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  • What am I missing about WCF?

    - by Bigtoe
    I've been developing in MS technologies for longer than I care to remember at this stage. When .NET arrived on the scene I thought they hit the nail on the head and with each iteration and version I thought their technologies were getting stronger and stronger and looked forward to each release. However, having had to work with WCF for the last year I must say I found the technology very difficult to work with and understand. Initially it's quite appealing but when you start getting into the guts of it, configuration is a nightmare, having to override behaviours for message sizes, number of objects contained in a messages, the complexity of the security model, disposing of proxies when faulted and finally moving back to defining interfaces in code rather than in XML. It just does not work out of the box and I think it should. We found all of the above issues while either testing ourselves or else when our products were out on site. I do understand the rationale behind it all, but surely they could have come up with simpler implementation mechanism. I suppose what I'm asking is, Am I looking at WCF the wrong way? What strengths does it have over the alternatives? Under what circumstances should I choose to use WCF? OK Folks, Sorry about the delay in responding, work does have a nasty habbit of get in the way somethimes :) Some clarifications My main paint point with WCF I suppose falls down into the following areas While it does work out of the box, your left with some major surprises under the hood. As pointed out above basic things are restricted until they are overridden Size of string than can be passed can't be over 8K Number of objects that can be passed in a single message is restricted Proxies not automatically recovering from failures The amount of configuration while it's there is a good thing, but understanding it all and what to use what and under which circumstances can be difficult to understand. Especially when deploying software on site with different security requirements etc. When talking about configuration, we've had to hide lots of ours in a back-end database because security and network people on-site were trying to change things in configuration files without understanding it. Keeping the configuration of the interfaces in code rather than moving to explicitly defined interfaces in XML, which can be published and consumed by almost anything. I know we can export the XML from the assembley, but it's full of rubbish and certain code generators choke on it. I know the world moves on, I've moved on a number of times over the last (ahem 22 years I've been developing) and am actively using WCF, so don't get me wrong, I do understand what it's for and where it's heading. I just think there should be simplier configuration/deployment options available, easier set-up and better management for configuration (SQL config provider maybe, rahter than just the web.config/app.config files). OK, back to the daily grid. Thanks for all your replies so far. Kind Regards Noel

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  • QT vs. Net - REAL comparisons for R.A.D. projects

    - by Pirate for Profit
    Man in all these Qt vs. .NET discussions 90% these people argue about the dumbest crap. Trying to get a real comparison chart here, because I know a little about both frameworks but I don't know everything. I believe Qt and .NET both have strengths and weaknesses. This is to make a comparison that highlights these so people can make more informed decisions before embarking on a project, in the spirit of R.A.D. Event Handling In Qt the event handling system is very simple. You just emit signals when something cool happens and then catch them in slots. ie. // run some calculations, then emit valueChanged(30, false, 20.2); and then catching it, any object can make a slot to recieve that message easily void MyObj::valueChanged(int percent, bool ok, float timeRemaining). It's easy to "block" an event or "disconnect" when needed, and works seamlessly across threads... once you get the hang of it, it just seems a lot more natural and intuitive than the way the .NET event handling is set up (you know, void valueChanged(object sender, CustomEventArgs e). And I'm not just talking about syntax, because in the end the .NET anonymous delegates are the bomb. I'm also talking about in more than just reflection (because, yes, .NET obviously has much stronger reflection capabilities). I'm talking about in the way the system feels to a human being. Qt wins hands down for the simplest yet still flexible event handling system ever i m o. Plugins and such I do love some of the ease of C# compared to C++, as well as .NET's assembly architecture, even though it leads to a bunch of .dll's (there's ways to combine everything into a single exe though). That is a big bonus for modular projects, which are a PITA to import stuff in C++ as far as RAD is concerned. Database Ease of Doing Crap Also what about datasets and database manipulations. I think .net wins here but I'm not sure. Threading/Conccurency How do you guys think of the threading? In .NET, all I've ever done is make like a list of master worker threads with locks. I like QConcurrentFramework, you don't worry about locks or anything, and with the ease of the signal slot system across threads it's nice to get notified about the progress of things. QConcurrent is the simplest threading mechanism I've ever played with. Memory Usage Also what do you think of the overall memory usage comparison. Is the .NET garbage collector pretty on the ball and quick compared to the instantaneous nature of native memory management? Or does it just let programs leak up a storm and lag the computer then clean it up when it's about to really lag? Doesn't the just-in-time compiler make native code that is pretty good, like and that only happens the first time the program is run? However, I am a n00b who doesn't know what I'm talking about, please school me on the subject.

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  • DCVS + hosting for a startup commercial multiplatform phone app

    - by AG
    I'm in lean startup mode, working on a simple phone app that will be published initially as a iThingy app and an Android app with, possibly, Blackberry and Symbian versions to follow. I'm about to go from no repository to needing a central repository that up to 4 very part-time resources will be sharing. Two of us have no version control background, one has used Subversion, and I've used most of the major centralized VCS systems. I'm not going to be pushing the technical limitations of any VCS for a long time; I'm sure that any of the major systems would work fine. And the hosting accounts I've looked at seem reasonable. So I'm really focussed on minimizing the downside risks. That is, I'd like to find a stable setup that is easy to learn in general, easy to use from Windows/Eclipse, and won't paint me into any obvious corners for the next 12 months or so. A quick search of the web had led me to consider the following pairs of DVCS and hosting service, with what I think I'm hearing as their strengths and weaknesses (for my purposes): Bazaar/Launchpad -- My initial choice since I need to get more familiar with this pair for the Google Summer of Code mentoring I'm doing. But, whatever the technical merits, a non-starter for me because they are purely open source, no private repositories plans to purchase that I can see. Git/GitHub -- Git: Fast, light, ultimately flexible, but relatively less Windows friendly, Eclipse plugin (eGit) available but relatively young, GitHub: widely used, pricing is fine Mercurial/BitBucket -- Mercurial: a little less flexible, a little more Windows friendly, Eclipse plugin seems a bit more mature, BitBucket: widely used, pricing is fine, includes a wiki and an issue tracker that we might be able to use instead of something like BaseCamp, at least for a while. Mercurial/BitBucket seem like the winning pair so far for my particular situation; at least two of us are definitely going to be working mostly from Eclipse on Windows and reducing my own learning curve is a priority. ;-) But I have two specific questions: 1) Am I wrong about Bazaar/Launchpad and is there a viable, secure way to use them for proprietary code? 2) Any reason to think that the Mecurial/Bitbucket pair will end up being a headache for my Mac developer, soon, or for Blackberry or Symbian developers a little later? ag

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  • Are there compelling reasons not to use Groovy?

    - by Leonard H Martin
    I'm developing a LoB application in Java after a long absence from the platform (having spent the last 8 years or so entrenched in Fortran, C, a smidgin of C++ and latterly .Net). Java, the language, is not much changed from how I remember it. I like it's strengths and I can work around its weaknesses - the platform has grown and deciding upon the myriad of different frameworks which appear to do much the same thing as one another is a different story; but that can wait for another day - all-in-all I'm comfortable with Java. However, over the last couple of weeks I've become enamoured with Groovy, and purely from a selfish point of view: but not just because it makes development against the JVM a more succinct and entertaining (and, well, "groovy") proposition than Java (the language). What strikes me most about Groovy is its inherent maintainability. We all (I hope!) strive to write well documented, easy to understand code. However, sometimes the languages we use themselves defeat us. An example: in 2001 I wrote a library in C to translate EDIFACT EDI messages into ANSI X12 messages. This is not a particularly complicated process, if slightly involved, and I thought at the time I had documented the code properly - and I probably had - but some six years later when I revisited the project (and after becoming acclimatised to C#) I found myself lost in so much C boilerplate (mallocs, pointers, etc. etc.) that it took three days of thoughtful analysis before I finally understood what I'd been doing six years previously. This evening I've written about 2000 lines of Java (it is the day of rest, after all!). I've documented as best as I know how, but, but, of those 2000 lines of Java a significant proportion is Java boiler plate. This is where I see Groovy and other dynamic languages winning through - maintainability and later comprehension. Groovy lets you concentrate on your intent without getting bogged down on the platform specific implementation; it's almost, but not quite, self documenting. I see this as being a huge boon to me when I revisit my current project (which I'll port to Groovy asap) in several years time and to my successors who will inherit it and carry on the good work. So, are there any reasons not to use Groovy?

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  • Visiting the Emtel Data Centre

    Back in February at the first event of the Emtel Knowledge Series (EKS) I spoke to various people at Emtel about their data centre here on the island. I was trying to see whether it would be possible to arrange a meeting over there for a selected group of our community members. Well, let's say it like this... My first approach wasn't that promising and far from successful but during the following months there were more and more occasions to get in touch with the "right" contact persons at Emtel to make it happen... Setting up an appointment and pre-requisites The major improvement came during a Boot Camp for Windows Phone 8.1 App development organised by Microsoft Indian Ocean Islands in cooperation with Emtel at the Emtel World, Ebene. Apart from learning bits and pieces regarding Universal Apps I took the opportunity to get in touch with Arvin Lockee, Sales Executive - Data, during our lunch break. And this really kicked off the whole procedure. Prior to get access to the Emtel data centre it is requested that you provide full name and National ID of anyone going to visit. Also, it should be noted that there was only a limited amount of seats available. Anyways, packed with this information I posted through the usual social media channels. Responses came in very quickly and based on First-come, first-serve (FCFS) principle I noted down the details and forwarded them to Emtel in order to fix a date and time for the visit. In preparation on our side, all attendees exchanged contact details and we organised transport options to go to the data centre in Arsenal. The day before and on the day of our meeting, Arvin send me a reminder to check whether everything is still confirmed and ready to go... Of course, it was! Arriving at the Emtel Data Centre As I'm coming from Flic En Flac towards the North, we agreed that I'm going to pick up a couple of young fellows near the old post office in Port Louis. All went well, except that Sean eventually might be living in another time zone compared to the rest of us. Anyway, after some extended stop we were complete and arrived just in time in Arsenal to meet and greet with Ish and Veer. Again, Emtel is taking access procedures to their data centre very serious and the gate stayed close until all our IDs had been noted and compared to the list of registered attendees. Despite having a good laugh at the mixture of old and new ID cards it was a straight-forward processing. The ward was very helpful and guided us to the waiting area at the entrance section of the building. Shortly after we were welcomed by Kamlesh Bokhoree, the Data Centre Officer. He gave us brief introduction into the rules and regulations during our visit, like no photography allowed, not touching the buttons, and following his instructions through the whole visit. Of course! Inside the data centre Next, he explained us the multi-factor authentication system using a combination of bio-metric data, like finger print reader, and "classic" pin panel. The Emtel data centre provides multiple services and next to co-location for your own hardware they also offer storage options for your backup and archive data in their massive, fire-resistant vault. Very impressive to get to know about the considerations that have been done in choosing the right location and how to set up the whole premises. It should also be noted that there is 24/7 CCTV surveillance inside and outside the buildings. Strengths of the Emtel TIER 3 Data Centre, Mauritius Finally, we were guided into the first server room. And wow, the whole setup is cleverly planned and outlined in the architecture. From the false floor and ceilings in order to provide optimum air flow, over to the separation of cold and hot aisles between the full-size server racks, and of course the monitored air conditions in order to analyse and watch changes in temperature, smoke detection and other parameters. And not surprisingly everything has been implemented in two independent circuits. There is a standardised classification for the construction and operation of data centres world-wide, and the Emtel's one has been designed to be a TIER 4 building but due to the lack of an alternative power supplier on the island it is officially registered as a TIER 3 compliant data centre. Maybe in the long run there might be a second supplier of energy next to CEB... time will tell. Luckily, the data centre is integrated into the National Fibre Optic Gigabit Ring and Emtel already connects internationally through diverse undersea cable routes like SAFE & LION/LION2 out of Mauritius and through several other providers for onwards connectivity. The data centre is part of the National Fibre Optic Gigabit Ring and has redundant internet connectivity onwards. Meanwhile, Arvin managed to join our little group of geeks and he supported Kamlesh in answering our technical questions regarding the capacities and general operation of the data centre. Visiting the NOC and its dedicated team of IT professionals was surely one of the visual highlights. Seeing their wall of screens to monitor any kind of activities on the data lines, the managed servers and the activity in and around the building was great. Even though I'm using a multi-head setup since years I cannot keep it up with that setup... ;-) But I got a couple of ideas on how to improve my work spaces here at the office. Clear advantages of hosting your e-commerce and mobile backends locally After the completely isolated NOC area we continued our Q&A session with Kamlesh and Arvin in the second server room which is dedictated to shared environments. On first thought it should be well-noted that there is lots of space for full-sized racks and therefore co-location of your own hardware. Actually, given the feedback that there will be upcoming changes in prices the facilities at the Emtel data centre are getting more and more competitive and interesting for local companies, especially small and medium enterprises. After seeing this world-class infrastructure available on the island, I'm already considering of moving one of my root servers abroad to be co-located here on the island. This would provide an improved user experience in terms of site performance and latency. This would be a good improvement, especially for upcoming e-commerce solutions for two of my local clients. Later on, we actually started the conversation of additional services that could be a catalyst for the local market in order to attract more small and medium companies to take the data centre into their evaluations regarding online activities. Until today Emtel does not provide virtualised server environments but there might be ongoing plans in the future to cover this field as well. Emtel is a mobile operator and internet connectivity provider in the first place, entering a market of managed and virtualised server infrastructures including capacities in terms of cloud storage and computing are rather new and there is a continuous learning curve at Emtel, too. You cannot just jump into a new market and see how it works out... And I appreciate Emtel's approach towards a solid fundament and then building new services on top of that. Emtel as a future one-stop-shop service provider for all your internet and telecommunications needs. Emtel's promotional video about their TIER 3 data centre in Arsenal, Mauritius More details are thoroughly described in Emtel's brochure of their data centre. Check out their PDF document here. Thanks for this opportunity Visiting and walking through the Emtel data centre for more than 2 hours was a great experience. As representative of the Mauritius Software Craftsmanship Community (MSCC) I would like to thank anyone at Emtel involved in the process of making it happen, and especially to Arvin Lockee and Kamlesh Bokhoree for their time and patience in explaining the infrastructure and answering all the endless questions from our members. Thank You!

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  • Cloud Computing = Elasticity * Availability

    - by Herve Roggero
    What is cloud computing? Is hosting the same thing as cloud computing? Are you running a cloud if you already use virtual machines? What is the difference between Infrastructure as a Service (IaaS) and a cloud provider? And the list goes on… these questions keep coming up and all try to fundamentally explain what “cloud” means relative to other concepts. At the risk of over simplification, answering these questions becomes simpler once you understand the primary foundations of cloud computing: Elasticity and Availability.   Elasticity The basic value proposition of cloud computing is to pay as you go, and to pay for what you use. This implies that an application can expand and contract on demand, across all its tiers (presentation layer, services, database, security…).  This also implies that application components can grow independently from each other. So if you need more storage for your database, you should be able to grow that tier without affecting, reconfiguring or changing the other tiers. Basically, cloud applications behave like a sponge; when you add water to a sponge, it grows in size; in the application world, the more customers you add, the more it grows. Pure IaaS providers will provide certain benefits, specifically in terms of operating costs, but an IaaS provider will not help you in making your applications elastic; neither will Virtual Machines. The smallest elasticity unit of an IaaS provider and a Virtual Machine environment is a server (physical or virtual). While adding servers in a datacenter helps in achieving scale, it is hardly enough. The application has yet to use this hardware.  If the process of adding computing resources is not transparent to the application, the application is not elastic.   As you can see from the above description, designing for the cloud is not about more servers; it is about designing an application for elasticity regardless of the underlying server farm.   Availability The fact of the matter is that making applications highly available is hard. It requires highly specialized tools and trained staff. On top of it, it's expensive. Many companies are required to run multiple data centers due to high availability requirements. In some organizations, some data centers are simply on standby, waiting to be used in a case of a failover. Other organizations are able to achieve a certain level of success with active/active data centers, in which all available data centers serve incoming user requests. While achieving high availability for services is relatively simple, establishing a highly available database farm is far more complex. In fact it is so complex that many companies establish yearly tests to validate failover procedures.   To a certain degree certain IaaS provides can assist with complex disaster recovery planning and setting up data centers that can achieve successful failover. However the burden is still on the corporation to manage and maintain such an environment, including regular hardware and software upgrades. Cloud computing on the other hand removes most of the disaster recovery requirements by hiding many of the underlying complexities.   Cloud Providers A cloud provider is an infrastructure provider offering additional tools to achieve application elasticity and availability that are not usually available on-premise. For example Microsoft Azure provides a simple configuration screen that makes it possible to run 1 or 100 web sites by clicking a button or two on a screen (simplifying provisioning), and soon SQL Azure will offer Data Federation to allow database sharding (which allows you to scale the database tier seamlessly and automatically). Other cloud providers offer certain features that are not available on-premise as well, such as the Amazon SC3 (Simple Storage Service) which gives you virtually unlimited storage capabilities for simple data stores, which is somewhat equivalent to the Microsoft Azure Table offering (offering a server-independent data storage model). Unlike IaaS providers, cloud providers give you the necessary tools to adopt elasticity as part of your application architecture.    Some cloud providers offer built-in high availability that get you out of the business of configuring clustered solutions, or running multiple data centers. Some cloud providers will give you more control (which puts some of that burden back on the customers' shoulder) and others will tend to make high availability totally transparent. For example, SQL Azure provides high availability automatically which would be very difficult to achieve (and very costly) on premise.   Keep in mind that each cloud provider has its strengths and weaknesses; some are better at achieving transparent scalability and server independence than others.    Not for Everyone Note however that it is up to you to leverage the elasticity capabilities of a cloud provider, as discussed previously; if you build a website that does not need to scale, for which elasticity is not important, then you can use a traditional host provider unless you also need high availability. Leveraging the technologies of cloud providers can be difficult and can become a journey for companies that build their solutions in a scale up fashion. Cloud computing promises to address cost containment and scalability of applications with built-in high availability. If your application does not need to scale or you do not need high availability, then cloud computing may not be for you. In fact, you may pay a premium to run your applications with cloud providers due to the underlying technologies built specifically for scalability and availability requirements. And as such, the cloud is not for everyone.   Consistent Customer Experience, Predictable Cost With all its complexities, buzz and foggy definition, cloud computing boils down to a simple objective: consistent customer experience at a predictable cost.  The objective of a cloud solution is to provide the same user experience to your last customer than the first, while keeping your operating costs directly proportional to the number of customers you have. Making your applications elastic and highly available across all its tiers, with as much automation as possible, achieves the first objective of a consistent customer experience. And the ability to expand and contract the infrastructure footprint of your application dynamically achieves the cost containment objectives.     Herve Roggero is a SQL Azure MVP and co-author of Pro SQL Azure (APress).  He is the co-founder of Blue Syntax Consulting (www.bluesyntax.net), a company focusing on cloud computing technologies helping customers understand and adopt cloud computing technologies. For more information contact herve at hroggero @ bluesyntax.net .

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  • What's new in Solaris 11.1?

    - by Karoly Vegh
    Solaris 11.1 is released. This is the first release update since Solaris 11 11/11, the versioning has been changed from MM/YY style to 11.1 highlighting that this is Solaris 11 Update 1.  Solaris 11 itself has been great. What's new in Solaris 11.1? Allow me to pick some new features from the What's New PDF that can be found in the official Oracle Solaris 11.1 Documentation. The updates are very numerous, I really can't include all.  I. New AI Automated Installer RBAC profiles have been introduced to enable delegation of installation tasks. II. The interactive installer now supports installing the OS to iSCSI targets. III. ASR (Auto Service Request) and OCM (Oracle Configuration Manager) have been enabled by default to proactively provide support information and create service requests to speed up support processes. This is optional and can be disabled but helps a lot in supportcases. For further information, see: http://oracle.com/goto/solarisautoreg IV. The new command svcbundle helps you to create SMF manifests without having to struggle with XML editing. (btw, do you know the interactive editprop subcommand in svccfg? The listprop/setprop subcommands are great for scripting and automating, but for an interactive property editing session try, for example, this: svccfg -s svc:/application/pkg/system-repository:default editprop )  V. pfedit: Ever wondered how to delegate editing permissions to certain files? It is well known "sudo /usr/bin/vi /etc/hosts" is not the right way, for sudo elevates the complete vi process to admin levels, and the user can "break" out of the session as root with simply starting a shell from that vi. Now, the new pfedit command provides a solution exactly to this challenge - an auditable, secure, per-user configurable editing possibility. See the pfedit man page for examples.   VI. rsyslog, the popular logging daemon (filters, SSL, formattable output, SQL collect...) has been included in Solaris 11.1 as an alternative to syslog.  VII: Zones: Solaris Zones - as a major Solaris differentiator - got lots of love in terms of new features: ZOSS - Zones on Shared Storage: Placing your zones to shared storage (FC, iSCSI) has never been this easy - via zonecfg.  parallell updates - with S11's bootenvironments updating zones was no problem and meant no downtime anyway, but still, now you can update them parallelly, a way faster update action if you are running a large number of zones. This is like parallell patching in Solaris 10, but with all the IPS/ZFS/S11 goodness.  per-zone fstype statistics: Running zones on a shared filesystems complicate the I/O debugging, since ZFS collects all the random writes and delivers them sequentially to boost performance. Now, over kstat you can find out which zone's I/O has an impact on the other ones, see the examples in the documentation: http://docs.oracle.com/cd/E26502_01/html/E29024/gmheh.html#scrolltoc Zones got RDSv3 protocol support for InfiniBand, and IPoIB support with Crossbow's anet (automatic vnic creation) feature.  NUMA I/O support for Zones: customers can now determine the NUMA I/O topology of the system from within zones.  VIII: Security got a lot of attention too:  Automated security/audit reporting, with builtin reporting templates e.g. for PCI (payment card industry) audits.  PAM is now configureable on a per-user basis instead of system wide, allowing different authentication requirements for different users  SSH in Solaris 11.1 now supports running in FIPS 140-2 mode, that is, in a U.S. government security accredited fashion.  SHA512/224 and SHA512/256 cryptographic hash functions are implemented in a FIPS-compliant way - and on a T4 implemented in silicon! That is, goverment-approved cryptography at HW-speed.  Generally, Solaris is currently under evaluation to be both FIPS and Common Criteria certified.  IX. Networking, as one of the core strengths of Solaris 11, has been extended with:  Data Center Bridging (DCB) - not only setups where network and storage share the same fabric (FCoE, anyone?) can have Quality-of-Service requirements. DCB enables peers to distinguish traffic based on priorities. Your NICs have to support DCB, see the documentation, and additional information on Wikipedia. DataLink MultiPathing, DLMP, enables link aggregation to span across multiple switches, even between those of different vendors. But there are essential differences to the good old bandwidth-aggregating LACP, see the documentation: http://docs.oracle.com/cd/E26502_01/html/E28993/gmdlu.html#scrolltoc VNIC live migration is now supported from one physical NIC to another on-the-fly  X. Data management:  FedFS, (Federated FileSystem) is new, it relies on Solaris 11's NFS referring mechanism to join separate shares of different NFS servers into a single filesystem namespace. The referring system has been there since S11 11/11, in Solaris 11.1 FedFS uses a LDAP - as the one global nameservice to bind them all.  The iSCSI initiator now uses the T4 CPU's HW-implemented CRC32 algorithm - thus improving iSCSI throughput while reducing CPU utilization on a T4 Storage locking improvements are now RAC aware, speeding up throughput with better locking-communication between nodes up to 20%!  XI: Kernel performance optimizations: The new Virtual Memory subsystem ("VM2") scales now to 100+ TB Memory ranges.  The memory predictor monitors large memory page usage, and adjust memory page sizes to applications' needs OSM, the Optimized Shared Memory allows Oracle DBs' SGA to be resized online XII: The Power Aware Dispatcher in now by default enabled, reducing power consumption of idle CPUs. Also, the LDoms' Power Management policies and the poweradm settings in Solaris 11 OS will cooperate. XIII: x86 boot: upgrade to the (Grand Unified Bootloader) GRUB2. Because grub2 differs in the configuration syntactically from grub1, one shall not edit the new grub configuration (grub.cfg) but use the new bootadm features to update it. GRUB2 adds UEFI support and also support for disks over 2TB. XIV: Improved viewing of per-CPU statistics of mpstat. This one might seem of less importance at first, but nowadays having better sorting/filtering possibilities on a periodically updated mpstat output of 256+ vCPUs can be a blessing. XV: Support for Solaris Cluster 4.1: The What's New document doesn't actually mention this one, since OSC 4.1 has not been released at the time 11.1 was. But since then it is available, and it requires Solaris 11.1. And it's only a "pkg update" away. ...aand I seriously need to stop here. There's a lot I missed, Edge Virtual Bridging, lofi tuning, ZFS sharing and crypto enhancements, USB3.0, pulseaudio, trusted extensions updates, etc - but if I mention all those then I effectively copy the What's New document. Which I recommend reading now anyway, it is a great extract of the 300+ new projects and RFE-followups in S11.1. And this blogpost is a summary of that extract.  For closing words, allow me to come back to Request For Enhancements, RFEs. Any customer can request features. Open up a Support Request, explain that this is an RFE, describe the feature you/your company desires to have in S11 implemented. The more SRs are collected for an RFE, the more chance it's got to get implemented. Feel free to provide feedback about the product, as well as about the Solaris 11.1 Documentation using the "Feedback" button there. Both the Solaris engineers and the documentation writers are eager to hear your input.Feel free to comment about this post too. Except that it's too long ;)  wbr,charlie

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  • Organization &amp; Architecture UNISA Studies &ndash; Chap 4

    - by MarkPearl
    Learning Outcomes Explain the characteristics of memory systems Describe the memory hierarchy Discuss cache memory principles Discuss issues relevant to cache design Describe the cache organization of the Pentium Computer Memory Systems There are key characteristics of memory… Location – internal or external Capacity – expressed in terms of bytes Unit of Transfer – the number of bits read out of or written into memory at a time Access Method – sequential, direct, random or associative From a users perspective the two most important characteristics of memory are… Capacity Performance – access time, memory cycle time, transfer rate The trade off for memory happens along three axis… Faster access time, greater cost per bit Greater capacity, smaller cost per bit Greater capacity, slower access time This leads to people using a tiered approach in their use of memory   As one goes down the hierarchy, the following occurs… Decreasing cost per bit Increasing capacity Increasing access time Decreasing frequency of access of the memory by the processor The use of two levels of memory to reduce average access time works in principle, but only if conditions 1 to 4 apply. A variety of technologies exist that allow us to accomplish this. Thus it is possible to organize data across the hierarchy such that the percentage of accesses to each successively lower level is substantially less than that of the level above. A portion of main memory can be used as a buffer to hold data temporarily that is to be read out to disk. This is sometimes referred to as a disk cache and improves performance in two ways… Disk writes are clustered. Instead of many small transfers of data, we have a few large transfers of data. This improves disk performance and minimizes processor involvement. Some data designed for write-out may be referenced by a program before the next dump to disk. In that case the data is retrieved rapidly from the software cache rather than slowly from disk. Cache Memory Principles Cache memory is substantially faster than main memory. A caching system works as follows.. When a processor attempts to read a word of memory, a check is made to see if this in in cache memory… If it is, the data is supplied, If it is not in the cache, a block of main memory, consisting of a fixed number of words is loaded to the cache. Because of the phenomenon of locality of references, when a block of data is fetched into the cache, it is likely that there will be future references to that same memory location or to other words in the block. Elements of Cache Design While there are a large number of cache implementations, there are a few basic design elements that serve to classify and differentiate cache architectures… Cache Addresses Cache Size Mapping Function Replacement Algorithm Write Policy Line Size Number of Caches Cache Addresses Almost all non-embedded processors support virtual memory. Virtual memory in essence allows a program to address memory from a logical point of view without needing to worry about the amount of physical memory available. When virtual addresses are used the designer may choose to place the cache between the MMU (memory management unit) and the processor or between the MMU and main memory. The disadvantage of virtual memory is that most virtual memory systems supply each application with the same virtual memory address space (each application sees virtual memory starting at memory address 0), which means the cache memory must be completely flushed with each application context switch or extra bits must be added to each line of the cache to identify which virtual address space the address refers to. Cache Size We would like the size of the cache to be small enough so that the overall average cost per bit is close to that of main memory alone and large enough so that the overall average access time is close to that of the cache alone. Also, larger caches are slightly slower than smaller ones. Mapping Function Because there are fewer cache lines than main memory blocks, an algorithm is needed for mapping main memory blocks into cache lines. The choice of mapping function dictates how the cache is organized. Three techniques can be used… Direct – simplest technique, maps each block of main memory into only one possible cache line Associative – Each main memory block to be loaded into any line of the cache Set Associative – exhibits the strengths of both the direct and associative approaches while reducing their disadvantages For detailed explanations of each approach – read the text book (page 148 – 154) Replacement Algorithm For associative and set associating mapping a replacement algorithm is needed to determine which of the existing blocks in the cache must be replaced by a new block. There are four common approaches… LRU (Least recently used) FIFO (First in first out) LFU (Least frequently used) Random selection Write Policy When a block resident in the cache is to be replaced, there are two cases to consider If no writes to that block have happened in the cache – discard it If a write has occurred, a process needs to be initiated where the changes in the cache are propagated back to the main memory. There are several approaches to achieve this including… Write Through – all writes to the cache are done to the main memory as well at the point of the change Write Back – when a block is replaced, all dirty bits are written back to main memory The problem is complicated when we have multiple caches, there are techniques to accommodate for this but I have not summarized them. Line Size When a block of data is retrieved and placed in the cache, not only the desired word but also some number of adjacent words are retrieved. As the block size increases from very small to larger sizes, the hit ratio will at first increase because of the principle of locality, which states that the data in the vicinity of a referenced word are likely to be referenced in the near future. As the block size increases, more useful data are brought into cache. The hit ratio will begin to decrease as the block becomes even bigger and the probability of using the newly fetched information becomes less than the probability of using the newly fetched information that has to be replaced. Two specific effects come into play… Larger blocks reduce the number of blocks that fit into a cache. Because each block fetch overwrites older cache contents, a small number of blocks results in data being overwritten shortly after they are fetched. As a block becomes larger, each additional word is farther from the requested word and therefore less likely to be needed in the near future. The relationship between block size and hit ratio is complex, and no set approach is judged to be the best in all circumstances.   Pentium 4 and ARM cache organizations The processor core consists of four major components: Fetch/decode unit – fetches program instruction in order from the L2 cache, decodes these into a series of micro-operations, and stores the results in the L2 instruction cache Out-of-order execution logic – Schedules execution of the micro-operations subject to data dependencies and resource availability – thus micro-operations may be scheduled for execution in a different order than they were fetched from the instruction stream. As time permits, this unit schedules speculative execution of micro-operations that may be required in the future Execution units – These units execute micro-operations, fetching the required data from the L1 data cache and temporarily storing results in registers Memory subsystem – This unit includes the L2 and L3 caches and the system bus, which is used to access main memory when the L1 and L2 caches have a cache miss and to access the system I/O resources

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  • Finding the Right Solution to Source and Manage Your Contractors

    - by mark.rosenberg(at)oracle.com
    Many of our PeopleSoft Enterprise applications customers operate in service-based industries, and all of our customers have at least some internal service units, such as IT, marketing, and facilities. Employing the services of contractors, often referred to as "contingent labor," to deliver either or both internal and external services is common practice. As we've transitioned from an industrial age to a knowledge age, talent has become a primary competitive advantage for most organizations. Contingent labor offers talent on flexible terms; it offers the ability to scale up operations, close skill gaps, and manage risk in the process of delivering services. Talent comes from many sources and the rise in the contingent worker (contractor, consultant, temporary, part time) has increased significantly in the past decade and is expected to reach 40 percent in the next decade. Managing the total pool of talent in a seamless integrated fashion not only saves organizations money and increases efficiency, but creates a better place for workers of all kinds to work. Although the term "contingent labor" is frequently used to describe both contractors and employees who have flexible schedules and relationships with an organization, the remainder of this discussion focuses on contractors. The term "contingent labor" is used interchangeably with "contractor." Recognizing the importance of contingent labor, our PeopleSoft customers often ask our team, "What Oracle vendor management system (VMS) applications should I evaluate for managing contractors?" In response, I thought it would be useful to describe and compare the three most common Oracle-based options available to our customers. They are:   The enterprise licensed software model in which you implement and utilize the PeopleSoft Services Procurement (sPro) application and potentially other PeopleSoft applications;  The software-as-a-service model in which you gain access to a derivative of PeopleSoft sPro from an Oracle Business Process Outsourcing Partner; and  The managed service provider (MSP) model in which staffing industry professionals utilize either your enterprise licensed software or the software-as-a-service application to administer your contingent labor program. At this point, you may be asking yourself, "Why three options?" The answer is that since there is no "one size fits all" in terms of talent, there is also no "one size fits all" for effectively sourcing and managing contingent workers. Various factors influence how an organization thinks about and relates to its contractors, and each of the three Oracle-based options addresses an organization's needs and preferences differently. For the purposes of this discussion, I will describe the options with respect to (A) pricing and software provisioning models; (B) control and flexibility; (C) level of engagement with contractors; and (D) approach to sourcing, employment law, and financial settlement. Option 1:  Enterprise Licensed Software In this model, you purchase from Oracle the license and support for the applications you need. Typically, you license PeopleSoft sPro as your VMS tool for sourcing, monitoring, and paying your contract labor. In conjunction with sPro, you can also utilize PeopleSoft Human Capital Management (HCM) applications (if you do not already) to configure more advanced business processes for recruiting, training, and tracking your contractors. Many customers choose this enterprise license software model because of the functionality and natural integration of the PeopleSoft applications and because the cost for the PeopleSoft software is explicit. There is no fee per transaction to source each contractor under this model. Our customers that employ contractors to augment their permanent staff on billable client engagements often find this model appealing because there are no fees to affect their profit margins. With this model, you decide whether to have your own IT organization run the software or have the software hosted and managed by either Oracle or another application services provider. Your organization, perhaps with the assistance of consultants, configures, deploys, and operates the software for managing your contingent workforce. This model offers you the highest level of control and flexibility since your organization can configure the contractor process flow exactly to your business and security requirements and can extend the functionality with PeopleTools. This option has proven very valuable and applicable to our customers engaged in government contracting because their contingent labor management practices are subject to complex standards and regulations. Customers find a great deal of value in the application functionality and configurability the enterprise licensed software offers for managing contingent labor. Some examples of that functionality are... The ability to create a tiered network of preferred suppliers including competencies, pricing agreements, and elaborate candidate management capabilities. Configurable alerts and online collaboration for bid, resource requisition, timesheet, and deliverable entry, routing, and approval for both resource and deliverable-based services. The ability to manage contractors with the same PeopleSoft HCM and Projects applications that are used to manage the permanent workforce. Because it allows you to utilize much of the same PeopleSoft HCM and Projects application functionality for contractors that you use for permanent employees, the enterprise licensed software model supports the deepest level of engagement with the contingent workforce. For example, you can: fill job openings with contingent labor; guide contingent workers through essential safety and compliance training with PeopleSoft Enterprise Learning Management; and source contingent workers directly to project-based assignments in PeopleSoft Resource Management and PeopleSoft Program Management. This option enables contingent workers to collaborate closely with your permanent staff on complex, knowledge-based efforts - R&D projects, billable client contracts, architecture and engineering projects spanning multiple years, and so on. With the enterprise licensed software model, your organization maintains responsibility for the sourcing, onboarding (including adherence to employment laws), and financial settlement processes. This means your organization maintains on staff or hires the expertise in these domains to utilize the software and interact with suppliers and contractors. Option 2:  Software as a Service (SaaS) The effort involved in setting up and operating VMS software to handle a contingent workforce leads many organizations to seek a system that can be activated and configured within a few days and for which they can pay based on usage. Oracle's Business Process Outsourcing partner, Provade, Inc., provides exactly this option to our customers. Provade offers its vendor management software as a service over the Internet and usually charges your organization a fee that is a percentage of your total contingent labor spending processed through the Provade software. (Percentage of spend is the predominant fee model, although not the only one.) In addition to lower implementation costs, the effort of configuring and maintaining the software is largely upon Provade, not your organization. This can be very appealing to IT organizations that are thinly stretched supporting other important information technology initiatives. Built upon PeopleSoft sPro, the Provade solution is tailored for simple and quick deployment and administration. Provade has added capabilities to clone users rapidly and has simplified business documents, like work orders and change orders, to facilitate enterprise-wide, self-service adoption with little to no training. Provade also leverages Oracle Business Intelligence Enterprise Edition (OBIEE) to provide integrated spend analytics and dashboards. Although pure customization is more limited than with the enterprise licensed software model, Provade offers a very effective option for organizations that are regularly on-boarding and off-boarding high volumes of contingent staff hired to perform discrete support tasks (for example, order fulfillment during the holiday season, hourly clerical work, desktop technology repairs, and so on) or project tasks. The software is very configurable and at the same time very intuitive to even the most computer-phobic users. The level of contingent worker engagement your organization can achieve with the Provade option is generally the same as with the enterprise licensed software model since Provade can automatically establish contingent labor resources in your PeopleSoft applications. Provade has pre-built integrations to Oracle's PeopleSoft and the Oracle E-Business Suite procurement, projects, payables, and HCM applications, so that you can evaluate, train, assign, and track contingent workers like your permanent employees. Similar to the enterprise licensed software model, your organization is responsible for the contingent worker sourcing, administration, and financial settlement processes. This means your organization needs to maintain the staff expertise in these domains. Option 3:  Managed Services Provider (MSP) Whether you are using the enterprise licensed model or the SaaS model, you may want to engage the services of sourcing, employment, payroll, and financial settlement professionals to administer your contingent workforce program. Firms that offer this expertise are often referred to as "MSPs," and they are typically staffing companies that also offer permanent and temporary hiring services. (In fact, many of the major MSPs are Oracle applications customers themselves, and they utilize the PeopleSoft Solution for the Staffing Industry to run their own business operations.) Usually, MSPs place their staff on-site at your facilities, and they can utilize either your enterprise licensed PeopleSoft sPro application or the Provade VMS SaaS software to administer the network of suppliers providing contingent workers. When you utilize an MSP, there is a separate fee for the MSP's service that is typically funded by the participating suppliers of the contingent labor. Also in this model, the suppliers of the contingent labor (not the MSP) usually pay the contingent labor force. With an MSP, you are intentionally turning over business process control for the advantages associated with having someone else manage the processes. The software option you choose will to a certain extent affect your process flexibility; however, the MSPs are often able to adapt their processes to the unique demands of your business. When you engage an MSP, you will want to give some thought to the level of engagement and "partnering" you need with your contingent workforce. Because the MSP acts as an intermediary, it can be very valuable in handling high volume, routine contracting for which there is a relatively low need for "partnering" with the contingent workforce. However, if your organization (or part of your organization) engages contingent workers for high-profile client projects that require diplomacy, intensive amounts of interaction, and personal trust, introducing an MSP into the process may prove less effective than handling the process with your own staff. In fact, in many organizations, it is common to enlist an MSP to handle contractors working on internal projects and to have permanent employees handle the contractor relationships that affect the portion of the services portfolio focused on customer-facing, billable projects. One of the key advantages of enlisting an MSP is that you do not have to maintain the expertise required for orchestrating the sourcing, hiring, and paying of contingent workers.  These are the domain of the MSPs. If your own staff members are not prepared to manage the essential "overhead" processes associated with contingent labor, working with an MSP can make solid business sense. Proper administration of a contingent workforce can make the difference between project success and failure, operating profit and loss, and legal compliance and fines. Concluding Thoughts There is little doubt that thoughtfully and purposefully constructing a service delivery strategy that leverages the strengths of contingent workers can lead to better projects, deliverables, and business results. What requires a bit more thinking is determining the platform (or platforms) that will enable each part of your organization to best deliver on its mission.

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  • C#: Handling Notifications: inheritance, events, or delegates?

    - by James Michael Hare
    Often times as developers we have to design a class where we get notification when certain things happen. In older object-oriented code this would often be implemented by overriding methods -- with events, delegates, and interfaces, however, we have far more elegant options. So, when should you use each of these methods and what are their strengths and weaknesses? Now, for the purposes of this article when I say notification, I'm just talking about ways for a class to let a user know that something has occurred. This can be through any programmatic means such as inheritance, events, delegates, etc. So let's build some context. I'm sitting here thinking about a provider neutral messaging layer for the place I work, and I got to the point where I needed to design the message subscriber which will receive messages from the message bus. Basically, what we want is to be able to create a message listener and have it be called whenever a new message arrives. Now, back before the flood we would have done this via inheritance and an abstract class: 1:  2: // using inheritance - omitting argument null checks and halt logic 3: public abstract class MessageListener 4: { 5: private ISubscriber _subscriber; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber) 11: { 12: _subscriber = subscriber; 13: _messageThread = new Thread(MessageLoop); 14: _messageThread.Start(); 15: } 16:  17: // user will override this to process their messages 18: protected abstract void OnMessageReceived(Message msg); 19:  20: // handle the looping in the thread 21: private void MessageLoop() 22: { 23: while(!_isHalted) 24: { 25: // as long as processing, wait 1 second for message 26: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 27: if(msg != null) 28: { 29: OnMessageReceived(msg); 30: } 31: } 32: } 33: ... 34: } It seems so odd to write this kind of code now. Does it feel odd to you? Maybe it's just because I've gotten so used to delegation that I really don't like the feel of this. To me it is akin to saying that if I want to drive my car I need to derive a new instance of it just to put myself in the driver's seat. And yet, unquestionably, five years ago I would have probably written the code as you see above. To me, inheritance is a flawed approach for notifications due to several reasons: Inheritance is one of the HIGHEST forms of coupling. You can't seal the listener class because it depends on sub-classing to work. Because C# does not allow multiple-inheritance, I've spent my one inheritance implementing this class. Every time you need to listen to a bus, you have to derive a class which leads to lots of trivial sub-classes. The act of consuming a message should be a separate responsibility than the act of listening for a message (SRP). Inheritance is such a strong statement (this IS-A that) that it should only be used in building type hierarchies and not for overriding use-specific behaviors and notifications. Chances are, if a class needs to be inherited to be used, it most likely is not designed as well as it could be in today's modern programming languages. So lets look at the other tools available to us for getting notified instead. Here's a few other choices to consider. Have the listener expose a MessageReceived event. Have the listener accept a new IMessageHandler interface instance. Have the listener accept an Action<Message> delegate. Really, all of these are different forms of delegation. Now, .NET events are a bit heavier than the other types of delegates in terms of run-time execution, but they are a great way to allow others using your class to subscribe to your events: 1: // using event - ommiting argument null checks and halt logic 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private bool _isHalted = false; 6: private Thread _messageThread; 7:  8: // assign the subscriber and start the messaging loop 9: public MessageListener(ISubscriber subscriber) 10: { 11: _subscriber = subscriber; 12: _messageThread = new Thread(MessageLoop); 13: _messageThread.Start(); 14: } 15:  16: // user will override this to process their messages 17: public event Action<Message> MessageReceived; 18:  19: // handle the looping in the thread 20: private void MessageLoop() 21: { 22: while(!_isHalted) 23: { 24: // as long as processing, wait 1 second for message 25: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 26: if(msg != null && MessageReceived != null) 27: { 28: MessageReceived(msg); 29: } 30: } 31: } 32: } Note, now we can seal the class to avoid changes and the user just needs to provide a message handling method: 1: theListener.MessageReceived += CustomReceiveMethod; However, personally I don't think events hold up as well in this case because events are largely optional. To me, what is the point of a listener if you create one with no event listeners? So in my mind, use events when handling the notification is optional. So how about the delegation via interface? I personally like this method quite a bit. Basically what it does is similar to inheritance method mentioned first, but better because it makes it easy to split the part of the class that doesn't change (the base listener behavior) from the part that does change (the user-specified action after receiving a message). So assuming we had an interface like: 1: public interface IMessageHandler 2: { 3: void OnMessageReceived(Message receivedMessage); 4: } Our listener would look like this: 1: // using delegation via interface - omitting argument null checks and halt logic 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private IMessageHandler _handler; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber, IMessageHandler handler) 11: { 12: _subscriber = subscriber; 13: _handler = handler; 14: _messageThread = new Thread(MessageLoop); 15: _messageThread.Start(); 16: } 17:  18: // handle the looping in the thread 19: private void MessageLoop() 20: { 21: while(!_isHalted) 22: { 23: // as long as processing, wait 1 second for message 24: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 25: if(msg != null) 26: { 27: _handler.OnMessageReceived(msg); 28: } 29: } 30: } 31: } And they would call it by creating a class that implements IMessageHandler and pass that instance into the constructor of the listener. I like that this alleviates the issues of inheritance and essentially forces you to provide a handler (as opposed to events) on construction. Well, this is good, but personally I think we could go one step further. While I like this better than events or inheritance, it still forces you to implement a specific method name. What if that name collides? Furthermore if you have lots of these you end up either with large classes inheriting multiple interfaces to implement one method, or lots of small classes. Also, if you had one class that wanted to manage messages from two different subscribers differently, it wouldn't be able to because the interface can't be overloaded. This brings me to using delegates directly. In general, every time I think about creating an interface for something, and if that interface contains only one method, I start thinking a delegate is a better approach. Now, that said delegates don't accomplish everything an interface can. Obviously having the interface allows you to refer to the classes that implement the interface which can be very handy. In this case, though, really all you want is a method to handle the messages. So let's look at a method delegate: 1: // using delegation via delegate - omitting argument null checks and halt logic 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private Action<Message> _handler; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber, Action<Message> handler) 11: { 12: _subscriber = subscriber; 13: _handler = handler; 14: _messageThread = new Thread(MessageLoop); 15: _messageThread.Start(); 16: } 17:  18: // handle the looping in the thread 19: private void MessageLoop() 20: { 21: while(!_isHalted) 22: { 23: // as long as processing, wait 1 second for message 24: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 25: if(msg != null) 26: { 27: _handler(msg); 28: } 29: } 30: } 31: } Here the MessageListener now takes an Action<Message>.  For those of you unfamiliar with the pre-defined delegate types in .NET, that is a method with the signature: void SomeMethodName(Message). The great thing about delegates is it gives you a lot of power. You could create an anonymous delegate, a lambda, or specify any other method as long as it satisfies the Action<Message> signature. This way, you don't need to define an arbitrary helper class or name the method a specific thing. Incidentally, we could combine both the interface and delegate approach to allow maximum flexibility. Doing this, the user could either pass in a delegate, or specify a delegate interface: 1: // using delegation - give users choice of interface or delegate 2: public sealed class MessageListener 3: { 4: private ISubscriber _subscriber; 5: private Action<Message> _handler; 6: private bool _isHalted = false; 7: private Thread _messageThread; 8:  9: // assign the subscriber and start the messaging loop 10: public MessageListener(ISubscriber subscriber, Action<Message> handler) 11: { 12: _subscriber = subscriber; 13: _handler = handler; 14: _messageThread = new Thread(MessageLoop); 15: _messageThread.Start(); 16: } 17:  18: // passes the interface method as a delegate using method group 19: public MessageListener(ISubscriber subscriber, IMessageHandler handler) 20: : this(subscriber, handler.OnMessageReceived) 21: { 22: } 23:  24: // handle the looping in the thread 25: private void MessageLoop() 26: { 27: while(!_isHalted) 28: { 29: // as long as processing, wait 1 second for message 30: Message msg = _subscriber.Receive(TimeSpan.FromSeconds(1)); 31: if(msg != null) 32: { 33: _handler(msg); 34: } 35: } 36: } 37: } } This is the method I tend to prefer because it allows the user of the class to choose which method works best for them. You may be curious about the actual performance of these different methods. 1: Enter iterations: 2: 1000000 3:  4: Inheritance took 4 ms. 5: Events took 7 ms. 6: Interface delegation took 4 ms. 7: Lambda delegate took 5 ms. Before you get too caught up in the numbers, however, keep in mind that this is performance over over 1,000,000 iterations. Since they are all < 10 ms which boils down to fractions of a micro-second per iteration so really any of them are a fine choice performance wise. As such, I think the choice of what to do really boils down to what you're trying to do. Here's my guidelines: Inheritance should be used only when defining a collection of related types with implementation specific behaviors, it should not be used as a hook for users to add their own functionality. Events should be used when subscription is optional or multi-cast is desired. Interface delegation should be used when you wish to refer to implementing classes by the interface type or if the type requires several methods to be implemented. Delegate method delegation should be used when you only need to provide one method and do not need to refer to implementers by the interface name.

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  • Modern Java alternatives

    - by Ralph
    I'm not sure if stackoverflow is the best forum for this discussion. I have been a Java developer for 14 years and have written an enterprise-level (~500,000 line) Swing application that uses most of the standard library APIs. Recently, I have become disappointed with the progress that the language has made to "modernize" itself, and am looking for an alternative for ongoing development. I have considered moving to the .NET platform, but I have issues with using something the only runs well in Windows (I know about Mono, but that is still far behind Microsoft). I also plan on buying a new Macbook Pro as soon as Apple releases their new rumored Arrandale-based machines and want to develop in an environment that will feel "at home" in Unix/Linux. I have considered using Python or Ruby, but the standard Java library is arguably the largest of any modern language. In JVM-based languages, I looked at Groovy, but am disappointed with its performance. Rumor has it that with the soon-to-be released JDK7, with its InvokeDynamic instruction, this will improve, but I don't know how much. Groovy is also not truly a functional language, although it provides closures and some of the "functional" features on collections. It does not embrace immutability. I have narrowed my search down to two JVM-based alternatives: Scala and Clojure. Each has its strengths and weaknesses. I am looking for the stackoverflow readerships' opinions. I am not an expert at either of these languages; I have read 2 1/2 books on Scala and am currently reading Stu Halloway's book on Clojure. Scala is strongly statically typed. I know the dynamic language folks claim that static typing is a crutch for not doing unit testing, but it does provide a mechanism for compile-time location of a whole class of errors. Scala is more concise than Java, but not as much as Clojure. Scala's inter-operation with Java seems to be better than Clojure's, in that most Java operations are easier to do in Scala than in Clojure. For example, I can find no way in Clojure to create a non-static initialization block in a class derived from a Java superclass. For example, I like the Apache commons CLI library for command line argument parsing. In Java and Scala, I can create a new Options object and add Option items to it in an initialization block as follows (Java code): final Options options = new Options() { { addOption(new Option("?", "help", false, "Show this usage information"); // other options } }; I can't figure out how to the same thing in Clojure (except by using (doit...)), although that may reflect my lack of knowledge of the language. Clojure's collections are optimized for immutability. They rarely require copy-on-write semantics. I don't know if Scala's immutable collections are implemented using similar algorithms, but Rich Hickey (Clojure's inventor) goes out of his way to explain how that language's data structures are efficient. Clojure was designed from the beginning for concurrency (as was Scala) and with modern multi-core processors, concurrency takes on more importance, but I occasionally need to write simple non-concurrent utilities, and Scala code probably runs a little faster for these applications since it discourages, but does not prohibit, "simple" mutability. One could argue that one-off utilities do not have to be super-fast, but sometimes they do tasks that take hours or days to complete. I know that there is no right answer to this "question", but I thought I would open it up for discussion. If anyone has a suggestion for another JVM-based language that can be used for enterprise level development, please list it. Also, it is not my intent to start a flame war. Thanks, Ralph

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  • Modern alternatives to Java

    - by Ralph
    I have been a Java developer for 14 years and have written an enterprise-level (~500 kloc) Swing application that uses most of the standard library APIs. Recently, I have become disappointed with the progress that the language has made to "modernize" itself, and am looking for an alternative for ongoing development. I have considered moving to the .NET platform, but I have issues with using something the only runs well in Windows (I know about Mono, but that is still far behind Microsoft). I also plan on buying a new Macbook Pro as soon as Apple releases their new rumored Arrandale-based machines and want to develop in an environment that will feel "at home" in Unix/Linux. I have considered using Python or Ruby, but the standard Java library is arguably the largest of any modern language. In JVM-based languages, I looked at Groovy, but am disappointed with its performance. Rumor has it that with the soon-to-be released JDK7, with its InvokeDynamic instruction, this will improve, but I don't know how much. Groovy is also not truly a functional language, although it provides closures and some of the "functional" features on collections. It does not embrace immutability. I have narrowed my search down to two JVM-based alternatives: Scala and Clojure. Each has its strengths and weaknesses. I am looking for opinions. I am not an expert at either of these languages; I have read 2 1/2 books on Scala and am currently reading Stu Halloway's book on Clojure. Scala is strongly statically typed. I know the dynamic language folks claim that static typing is a crutch for not doing unit testing, but it does provide a mechanism for compile-time location of a whole class of errors. Scala is more concise than Java, but not as much as Clojure. Scala's inter-operation with Java seems to be better than Clojure's, in that most Java operations are easier to do in Scala than in Clojure. For example, I can find no way in Clojure to create a non-static initialization block in a class derived from a Java superclass. For example, I like the Apache commons CLI library for command line argument parsing. In Java and Scala, I can create a new Options object and add Option items to it in an initialization block as follows (Java code): final Options options = new Options() { { addOption(new Option("?", "help", false, "Show this usage information"); // other options } }; I can't figure out how to the same thing in Clojure (except by using (doit...)), although that may reflect my lack of knowledge of the language. Clojure's collections are optimized for immutability. They rarely require copy-on-write semantics. I don't know if Scala's immutable collections are implemented using similar algorithms, but Rich Hickey (Clojure's inventor) goes out of his way to explain how that language's data structures are efficient. Clojure was designed from the beginning for concurrency (as was Scala) and with modern multi-core processors, concurrency takes on more importance, but I occasionally need to write simple non-concurrent utilities, and Scala code probably runs a little faster for these applications since it discourages, but does not prohibit, "simple" mutability. One could argue that one-off utilities do not have to be super-fast, but sometimes they do tasks that take hours or days to complete. I know that there is no right answer to this "question", but I thought I would open it up for discussion. Are there other JVM-based languages that can be used for enterprise level development?

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  • Pain Comes Instantly

    - by user701213
    When I look back at recent blog entries – many of which are not all that current (more on where my available writing time is going later) – I am struck by how many of them focus on public policy or legislative issues instead of, say, the latest nefarious cyberattack or exploit (or everyone’s favorite new pastime: coining terms for the Coming Cyberpocalypse: “digital Pearl Harbor” is so 1941). Speaking of which, I personally hope evil hackers from Malefactoria will someday hack into my bathroom scale – which in a future time will be connected to the Internet because, gosh, wouldn’t it be great to have absolutely everything in your life Internet-enabled? – and recalibrate it so I’m 10 pounds thinner. The horror. In part, my focus on public policy is due to an admitted limitation of my skill set. I enjoy reading technical articles about exploits and cybersecurity trends, but writing a blog entry on those topics would take more research than I have time for and, quite honestly, doesn’t play to my strengths. The first rule of writing is “write what you know.” The bigger contributing factor to my recent paucity of blog entries is that more and more of my waking hours are spent engaging in “thrust and parry” activity involving emerging regulations of some sort or other. I’ve opined in earlier blogs about what constitutes good and reasonable public policy so nobody can accuse me of being reflexively anti-regulation. That said, you have so many cycles in the day, and most of us would rather spend it slaying actual dragons than participating in focus groups on whether dragons are really a problem, whether lassoing them (with organic, sustainable and recyclable lassos) is preferable to slaying them – after all, dragons are people, too - and whether we need lasso compliance auditors to make sure lassos are being used correctly and humanely. (A point that seems to evade many rule makers: slaying dragons actually accomplishes something, whereas talking about “approved dragon slaying procedures and requirements” wastes the time of those who are competent to dispatch actual dragons and who were doing so very well without the input of “dragon-slaying theorists.”) Unfortunately for so many of us who would just get on with doing our day jobs, cybersecurity is rapidly devolving into the “focus groups on dragon dispatching” realm, which actual dragons slayers have little choice but to participate in. The general trend in cybersecurity is that powers-that-be – which encompasses groups other than just legislators – are often increasingly concerned and therefore feel they need to Do Something About Cybersecurity. Many seem to believe that if only we had the right amount of regulation and oversight, there would be no data breaches: a breach simply must mean Someone Is At Fault and Needs Supervision. (Leaving aside the fact that we have lots of home invasions despite a) guard dogs b) liberal carry permits c) alarm systems d) etc.) Also note that many well-managed and security-aware organizations, like the US Department of Defense, still get hacked. More specifically, many powers-that-be feel they must direct industry in a multiplicity of ways, up to and including how we actually build and deploy information technology systems. The more prescriptive the requirement, the more regulators or overseers a) can be seen to be doing something b) feel as if they are doing something regardless of whether they are actually doing something useful or cost effective. Note: an unfortunate concomitant of Doing Something is that often the cure is worse than the ailment. That is, doing what overseers want creates unfortunate byproducts that they either didn’t foresee or worse, don’t care about. After all, the logic goes, we Did Something. Prescriptive practice in the IT industry is problematic for a number of reasons. For a start, prescriptive guidance is really only appropriate if: • It is cost effective• It is “current” (meaning, the guidance doesn’t require the use of the technical equivalent of buggy whips long after horse-drawn transportation has become passé)*• It is practical (that is, pragmatic, proven and effective in the real world, not theoretical and unproven)• It solves the right problem With the above in mind, heading up the list of “you must be joking” regulations are recent disturbing developments in the Payment Card Industry (PCI) world. I’d like to give PCI kahunas the benefit of the doubt about their intentions, except that efforts by Oracle among others to make them aware of “unfortunate side effects of your requirements” – which is as tactful I can be for reasons that I believe will become obvious below - have gone, to-date, unanswered and more importantly, unchanged. A little background on PCI before I get too wound up. In 2008, the Payment Card Industry (PCI) Security Standards Council (SSC) introduced the Payment Application Data Security Standard (PA-DSS). That standard requires vendors of payment applications to ensure that their products implement specific requirements and undergo security assessment procedures. In order to have an application listed as a Validated Payment Application (VPA) and available for use by merchants, software vendors are required to execute the PCI Payment Application Vendor Release Agreement (VRA). (Are you still with me through all the acronyms?) Beginning in August 2010, the VRA imposed new obligations on vendors that are extraordinary and extraordinarily bad, short-sighted and unworkable. Specifically, PCI requires vendors to disclose (dare we say “tell all?”) to PCI any known security vulnerabilities and associated security breaches involving VPAs. ASAP. Think about the impact of that. PCI is asking a vendor to disclose to them: • Specific details of security vulnerabilities • Including exploit information or technical details of the vulnerability • Whether or not there is any mitigation available (as in a patch) PCI, in turn, has the right to blab about any and all of the above – specifically, to distribute all the gory details of what is disclosed - to the PCI SSC, qualified security assessors (QSAs), and any affiliate or agent or adviser of those entities, who are in turn permitted to share it with their respective affiliates, agents, employees, contractors, merchants, processors, service providers and other business partners. This assorted crew can’t be more than, oh, hundreds of thousands of entities. Does anybody believe that several hundred thousand people can keep a secret? Or that several hundred thousand people are all equally trustworthy? Or that not one of the people getting all that information would blab vulnerability details to a bad guy, even by accident? Or be a bad guy who uses the information to break into systems? (Wait, was that the Easter Bunny that just hopped by? Bringing world peace, no doubt.) Sarcasm aside, common sense tells us that telling lots of people a secret is guaranteed to “unsecret” the secret. Notably, being provided details of a vulnerability (without a patch) is of little or no use to companies running the affected application. Few users have the technological sophistication to create a workaround, and even if they do, most workarounds break some other functionality in the application or surrounding environment. Also, given the differences among corporate implementations of any application, it is highly unlikely that a single workaround is going to work for all corporate users. So until a patch is developed by the vendor, users remain at risk of exploit: even more so if the details of vulnerability have been widely shared. Sharing that information widely before a patch is available therefore does not help users, and instead helps only those wanting to exploit known security bugs. There’s a shocker for you. Furthermore, we already know that insider information about security vulnerabilities inevitably leaks, which is why most vendors closely hold such information and limit dissemination until a patch is available (and frequently limit dissemination of technical details even with the release of a patch). That’s the industry norm, not that PCI seems to realize or acknowledge that. Why would anybody release a bunch of highly technical exploit information to a cast of thousands, whose only “vetting” is that they are members of a PCI consortium? Oracle has had personal experience with this problem, which is one reason why information on security vulnerabilities at Oracle is “need to know” (we use our own row level access control to limit access to security bugs in our bug database, and thus less than 1% of development has access to this information), and we don’t provide some customers with more information than others or with vulnerability information and/or patches earlier than others. Failure to remember “insider information always leaks” creates problems in the general case, and has created problems for us specifically. A number of years ago, one of the UK intelligence agencies had information about a non-public security vulnerability in an Oracle product that they circulated among other UK and Commonwealth defense and intelligence entities. Nobody, it should be pointed out, bothered to report the problem to Oracle, even though only Oracle could produce a patch. The vulnerability was finally reported to Oracle by (drum roll) a US-based commercial company, to whom the information had leaked. (Note: every time I tell this story, the MI-whatever agency that created the problem gets a bit shirty with us. I know they meant well and have improved their vulnerability handling/sharing processes but, dudes, next time you find an Oracle vulnerability, try reporting it to us first before blabbing to lots of people who can’t actually fix the problem. Thank you!) Getting back to PCI: clearly, these new disclosure obligations increase the risk of exploitation of a vulnerability in a VPA and thus, of misappropriation of payment card data and customer information that a VPA processes, stores or transmits. It stands to reason that VRA’s current requirement for the widespread distribution of security vulnerability exploit details -- at any time, but particularly before a vendor can issue a patch or a workaround -- is very poor public policy. It effectively publicizes information of great value to potential attackers while not providing compensating benefits - actually, any benefits - to payment card merchants or consumers. In fact, it magnifies the risk to payment card merchants and consumers. The risk is most prominent in the time before a patch has been released, since customers often have little option but to continue using an application or system despite the risks. However, the risk is not limited to the time before a patch is issued: customers often need days, or weeks, to apply patches to systems, based upon the complexity of the issue and dependence on surrounding programs. Rather than decreasing the available window of exploit, this requirement increases the available window of exploit, both as to time available to exploit a vulnerability and the ease with which it can be exploited. Also, why would hackers focus on finding new vulnerabilities to exploit if they can get “EZHack” handed to them in such a manner: a) a vulnerability b) in a payment application c) with exploit code: the “Hacking Trifecta!“ It’s fair to say that this is probably the exact opposite of what PCI – or any of us – would want. Established industry practice concerning vulnerability handling avoids the risks created by the VRA’s vulnerability disclosure requirements. Specifically, the norm is not to release information about a security bug until the associated patch (or a pretty darn good workaround) has been issued. Once a patch is available, the notice to the user community is a high-level communication discussing the product at issue, the level of risk associated with the vulnerability, and how to apply the patch. The notices do not include either the specific customers affected by the vulnerability or forensic reports with maps of the exploit (both of which are required by the current VRA). In this way, customers have the tools they need to prioritize patching and to help prevent an attack, and the information released does not increase the risk of exploit. Furthermore, many vendors already use industry standards for vulnerability description: Common Vulnerability Enumeration (CVE) and Common Vulnerability Scoring System (CVSS). CVE helps ensure that customers know which particular issues a patch addresses and CVSS helps customers determine how severe a vulnerability is on a relative scale. Industry already provides the tools customers need to know what the patch contains and how bad the problem is that the patch remediates. So, what’s a poor vendor to do? Oracle is reaching out to other vendors subject to PCI and attempting to enlist then in a broad effort to engage PCI in rethinking (that is, eradicating) these requirements. I would therefore urge all who care about this issue, but especially those in the vendor community whose applications are subject to PCI and who may not have know they were being asked to tell-all to PCI and put their customers at risk, to do one of the following: • Contact PCI with your concerns• Contact Oracle (we are looking for vendors to sign our statement of concern)• And make sure you tell your customers that you have to rat them out to PCI if there is a breach involving the payment application I like to be charitable and say “PCI meant well” but in as important a public policy issue as what you disclose about vulnerabilities, to whom and when, meaning well isn’t enough. We need to do well. PCI, as regards this particular issue, has not done well, and has compounded the error by thus far being nonresponsive to those of us who have labored mightily to try to explain why they might want to rethink telling the entire planet about security problems with no solutions. By Way of Explanation… Non-related to PCI whatsoever, and the explanation for why I have not been blogging a lot recently, I have been working on Other Writing Venues with my sister Diane (who has also worked in the tech sector, inflicting upgrades on unsuspecting and largely ungrateful end users). I am pleased to note that we have recently (self-)published the first in the Miss Information Technology Murder Mystery series, Outsourcing Murder. The genre might best be described as “chick lit meets geek scene.” Our sisterly nom de plume is Maddi Davidson and (shameless plug follows): you can order the paper version of the book on Amazon, or the Kindle or Nook versions on www.amazon.com or www.bn.com, respectively. From our book jacket: Emma Jones, a 20-something IT consultant, is working on an outsourcing project at Tahiti Tacos, a restaurant chain offering Polynexican cuisine: refried poi, anyone? Emma despises her boss Padmanabh, a brilliant but arrogant partner in GD Consulting. When Emma discovers His-Royal-Padness’s body (verdict: death by cricket bat), she becomes a suspect.With her overprotective family and her best friend Stacey providing endless support and advice, Emma stumbles her way through an investigation of Padmanabh’s murder, bolstered by fusion food feeding frenzies, endless cups of frou-frou coffee and serious surfing sessions. While Stacey knows a PI who owes her a favor, landlady Magda urges Emma to tart up her underwear drawer before the next cute cop with a search warrant arrives. Emma’s mother offers to fix her up with a PhD student at Berkeley and showers her with self-defense gizmos while her old lover Keoni beckons from Hawai’i. And everyone, even Shaun the barista, knows a good lawyer. Book 2, Denial of Service, is coming out this summer. * Given the rate of change in technology, today’s “thou shalts” are easily next year’s “buggy whip guidance.”

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  • ASP.NET Frameworks and Raw Throughput Performance

    - by Rick Strahl
    A few days ago I had a curious thought: With all these different technologies that the ASP.NET stack has to offer, what's the most efficient technology overall to return data for a server request? When I started this it was mere curiosity rather than a real practical need or result. Different tools are used for different problems and so performance differences are to be expected. But still I was curious to see how the various technologies performed relative to each just for raw throughput of the request getting to the endpoint and back out to the client with as little processing in the actual endpoint logic as possible (aka Hello World!). I want to clarify that this is merely an informal test for my own curiosity and I'm sharing the results and process here because I thought it was interesting. It's been a long while since I've done any sort of perf testing on ASP.NET, mainly because I've not had extremely heavy load requirements and because overall ASP.NET performs very well even for fairly high loads so that often it's not that critical to test load performance. This post is not meant to make a point  or even come to a conclusion which tech is better, but just to act as a reference to help understand some of the differences in perf and give a starting point to play around with this yourself. I've included the code for this simple project, so you can play with it and maybe add a few additional tests for different things if you like. Source Code on GitHub I looked at this data for these technologies: ASP.NET Web API ASP.NET MVC WebForms ASP.NET WebPages ASMX AJAX Services  (couldn't get AJAX/JSON to run on IIS8 ) WCF Rest Raw ASP.NET HttpHandlers It's quite a mixed bag, of course and the technologies target different types of development. What started out as mere curiosity turned into a bit of a head scratcher as the results were sometimes surprising. What I describe here is more to satisfy my curiosity more than anything and I thought it interesting enough to discuss on the blog :-) First test: Raw Throughput The first thing I did is test raw throughput for the various technologies. This is the least practical test of course since you're unlikely to ever create the equivalent of a 'Hello World' request in a real life application. The idea here is to measure how much time a 'NOP' request takes to return data to the client. So for this request I create the simplest Hello World request that I could come up for each tech. Http Handler The first is the lowest level approach which is an HTTP handler. public class Handler : IHttpHandler { public void ProcessRequest(HttpContext context) { context.Response.ContentType = "text/plain"; context.Response.Write("Hello World. Time is: " + DateTime.Now.ToString()); } public bool IsReusable { get { return true; } } } WebForms Next I added a couple of ASPX pages - one using CodeBehind and one using only a markup page. The CodeBehind page simple does this in CodeBehind without any markup in the ASPX page: public partial class HelloWorld_CodeBehind : System.Web.UI.Page { protected void Page_Load(object sender, EventArgs e) { Response.Write("Hello World. Time is: " + DateTime.Now.ToString() ); Response.End(); } } while the Markup page only contains some static output via an expression:<%@ Page Language="C#" AutoEventWireup="false" CodeBehind="HelloWorld_Markup.aspx.cs" Inherits="AspNetFrameworksPerformance.HelloWorld_Markup" %> Hello World. Time is <%= DateTime.Now %> ASP.NET WebPages WebPages is the freestanding Razor implementation of ASP.NET. Here's the simple HelloWorld.cshtml page:Hello World @DateTime.Now WCF REST WCF REST was the token REST implementation for ASP.NET before WebAPI and the inbetween step from ASP.NET AJAX. I'd like to forget that this technology was ever considered for production use, but I'll include it here. Here's an OperationContract class: [ServiceContract(Namespace = "")] [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)] public class WcfService { [OperationContract] [WebGet] public Stream HelloWorld() { var data = Encoding.Unicode.GetBytes("Hello World" + DateTime.Now.ToString()); var ms = new MemoryStream(data); // Add your operation implementation here return ms; } } WCF REST can return arbitrary results by returning a Stream object and a content type. The code above turns the string result into a stream and returns that back to the client. ASP.NET AJAX (ASMX Services) I also wanted to test ASP.NET AJAX services because prior to WebAPI this is probably still the most widely used AJAX technology for the ASP.NET stack today. Unfortunately I was completely unable to get this running on my Windows 8 machine. Visual Studio 2012  removed adding of ASP.NET AJAX services, and when I tried to manually add the service and configure the script handler references it simply did not work - I always got a SOAP response for GET and POST operations. No matter what I tried I always ended up getting XML results even when explicitly adding the ScriptHandler. So, I didn't test this (but the code is there - you might be able to test this on a Windows 7 box). ASP.NET MVC Next up is probably the most popular ASP.NET technology at the moment: MVC. Here's the small controller: public class MvcPerformanceController : Controller { public ActionResult Index() { return View(); } public ActionResult HelloWorldCode() { return new ContentResult() { Content = "Hello World. Time is: " + DateTime.Now.ToString() }; } } ASP.NET WebAPI Next up is WebAPI which looks kind of similar to MVC. Except here I have to use a StringContent result to return the response: public class WebApiPerformanceController : ApiController { [HttpGet] public HttpResponseMessage HelloWorldCode() { return new HttpResponseMessage() { Content = new StringContent("Hello World. Time is: " + DateTime.Now.ToString(), Encoding.UTF8, "text/plain") }; } } Testing Take a minute to think about each of the technologies… and take a guess which you think is most efficient in raw throughput. The fastest should be pretty obvious, but the others - maybe not so much. The testing I did is pretty informal since it was mainly to satisfy my curiosity - here's how I did this: I used Apache Bench (ab.exe) from a full Apache HTTP installation to run and log the test results of hitting the server. ab.exe is a small executable that lets you hit a URL repeatedly and provides counter information about the number of requests, requests per second etc. ab.exe and the batch file are located in the \LoadTests folder of the project. An ab.exe command line  looks like this: ab.exe -n100000 -c20 http://localhost/aspnetperf/api/HelloWorld which hits the specified URL 100,000 times with a load factor of 20 concurrent requests. This results in output like this:   It's a great way to get a quick and dirty performance summary. Run it a few times to make sure there's not a large amount of varience. You might also want to do an IISRESET to clear the Web Server. Just make sure you do a short test run to warm up the server first - otherwise your first run is likely to be skewed downwards. ab.exe also allows you to specify headers and provide POST data and many other things if you want to get a little more fancy. Here all tests are GET requests to keep it simple. I ran each test: 100,000 iterations Load factor of 20 concurrent connections IISReset before starting A short warm up run for API and MVC to make sure startup cost is mitigated Here is the batch file I used for the test: IISRESET REM make sure you add REM C:\Program Files (x86)\Apache Software Foundation\Apache2.2\bin REM to your path so ab.exe can be found REM Warm up ab.exe -n100 -c20 http://localhost/aspnetperf/MvcPerformance/HelloWorldJsonab.exe -n100 -c20 http://localhost/aspnetperf/api/HelloWorldJson ab.exe -n100 -c20 http://localhost/AspNetPerf/WcfService.svc/HelloWorld ab.exe -n100000 -c20 http://localhost/aspnetperf/handler.ashx > handler.txt ab.exe -n100000 -c20 http://localhost/aspnetperf/HelloWorld_CodeBehind.aspx > AspxCodeBehind.txt ab.exe -n100000 -c20 http://localhost/aspnetperf/HelloWorld_Markup.aspx > AspxMarkup.txt ab.exe -n100000 -c20 http://localhost/AspNetPerf/WcfService.svc/HelloWorld > Wcf.txt ab.exe -n100000 -c20 http://localhost/aspnetperf/MvcPerformance/HelloWorldCode > Mvc.txt ab.exe -n100000 -c20 http://localhost/aspnetperf/api/HelloWorld > WebApi.txt I ran each of these tests 3 times and took the average score for Requests/second, with the machine otherwise idle. I did see a bit of variance when running many tests but the values used here are the medians. Part of this has to do with the fact I ran the tests on my local machine - result would probably more consistent running the load test on a separate machine hitting across the network. I ran these tests locally on my laptop which is a Dell XPS with quad core Sandibridge I7-2720QM @ 2.20ghz and a fast SSD drive on Windows 8. CPU load during tests ran to about 70% max across all 4 cores (IOW, it wasn't overloading the machine). Ideally you can try running these tests on a separate machine hitting the local machine. If I remember correctly IIS 7 and 8 on client OSs don't throttle so the performance here should be Results Ok, let's cut straight to the chase. Below are the results from the tests… It's not surprising that the handler was fastest. But it was a bit surprising to me that the next fastest was WebForms and especially Web Forms with markup over a CodeBehind page. WebPages also fared fairly well. MVC and WebAPI are a little slower and the slowest by far is WCF REST (which again I find surprising). As mentioned at the start the raw throughput tests are not overly practical as they don't test scripting performance for the HTML generation engines or serialization performances of the data engines. All it really does is give you an idea of the raw throughput for the technology from time of request to reaching the endpoint and returning minimal text data back to the client which indicates full round trip performance. But it's still interesting to see that Web Forms performs better in throughput than either MVC, WebAPI or WebPages. It'd be interesting to try this with a few pages that actually have some parsing logic on it, but that's beyond the scope of this throughput test. But what's also amazing about this test is the sheer amount of traffic that a laptop computer is handling. Even the slowest tech managed 5700 requests a second, which is one hell of a lot of requests if you extrapolate that out over a 24 hour period. Remember these are not static pages, but dynamic requests that are being served. Another test - JSON Data Service Results The second test I used a JSON result from several of the technologies. I didn't bother running WebForms and WebPages through this test since that doesn't make a ton of sense to return data from the them (OTOH, returning text from the APIs didn't make a ton of sense either :-) In these tests I have a small Person class that gets serialized and then returned to the client. The Person class looks like this: public class Person { public Person() { Id = 10; Name = "Rick"; Entered = DateTime.Now; } public int Id { get; set; } public string Name { get; set; } public DateTime Entered { get; set; } } Here are the updated handler classes that use Person: Handler public class Handler : IHttpHandler { public void ProcessRequest(HttpContext context) { var action = context.Request.QueryString["action"]; if (action == "json") JsonRequest(context); else TextRequest(context); } public void TextRequest(HttpContext context) { context.Response.ContentType = "text/plain"; context.Response.Write("Hello World. Time is: " + DateTime.Now.ToString()); } public void JsonRequest(HttpContext context) { var json = JsonConvert.SerializeObject(new Person(), Formatting.None); context.Response.ContentType = "application/json"; context.Response.Write(json); } public bool IsReusable { get { return true; } } } This code adds a little logic to check for a action query string and route the request to an optional JSON result method. To generate JSON, I'm using the same JSON.NET serializer (JsonConvert.SerializeObject) used in Web API to create the JSON response. WCF REST   [ServiceContract(Namespace = "")] [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)] public class WcfService { [OperationContract] [WebGet] public Stream HelloWorld() { var data = Encoding.Unicode.GetBytes("Hello World " + DateTime.Now.ToString()); var ms = new MemoryStream(data); // Add your operation implementation here return ms; } [OperationContract] [WebGet(ResponseFormat=WebMessageFormat.Json,BodyStyle=WebMessageBodyStyle.WrappedRequest)] public Person HelloWorldJson() { // Add your operation implementation here return new Person(); } } For WCF REST all I have to do is add a method with the Person result type.   ASP.NET MVC public class MvcPerformanceController : Controller { // // GET: /MvcPerformance/ public ActionResult Index() { return View(); } public ActionResult HelloWorldCode() { return new ContentResult() { Content = "Hello World. Time is: " + DateTime.Now.ToString() }; } public JsonResult HelloWorldJson() { return Json(new Person(), JsonRequestBehavior.AllowGet); } } For MVC all I have to do for a JSON response is return a JSON result. ASP.NET internally uses JavaScriptSerializer. ASP.NET WebAPI public class WebApiPerformanceController : ApiController { [HttpGet] public HttpResponseMessage HelloWorldCode() { return new HttpResponseMessage() { Content = new StringContent("Hello World. Time is: " + DateTime.Now.ToString(), Encoding.UTF8, "text/plain") }; } [HttpGet] public Person HelloWorldJson() { return new Person(); } [HttpGet] public HttpResponseMessage HelloWorldJson2() { var response = new HttpResponseMessage(HttpStatusCode.OK); response.Content = new ObjectContent<Person>(new Person(), GlobalConfiguration.Configuration.Formatters.JsonFormatter); return response; } } Testing and Results To run these data requests I used the following ab.exe commands:REM JSON RESPONSES ab.exe -n100000 -c20 http://localhost/aspnetperf/Handler.ashx?action=json > HandlerJson.txt ab.exe -n100000 -c20 http://localhost/aspnetperf/MvcPerformance/HelloWorldJson > MvcJson.txt ab.exe -n100000 -c20 http://localhost/aspnetperf/api/HelloWorldJson > WebApiJson.txt ab.exe -n100000 -c20 http://localhost/AspNetPerf/WcfService.svc/HelloWorldJson > WcfJson.txt The results from this test run are a bit interesting in that the WebAPI test improved performance significantly over returning plain string content. Here are the results:   The performance for each technology drops a little bit except for WebAPI which is up quite a bit! From this test it appears that WebAPI is actually significantly better performing returning a JSON response, rather than a plain string response. Snag with Apache Benchmark and 'Length Failures' I ran into a little snag with Apache Benchmark, which was reporting failures for my Web API requests when serializing. As the graph shows performance improved significantly from with JSON results from 5580 to 6530 or so which is a 15% improvement (while all others slowed down by 3-8%). However, I was skeptical at first because the WebAPI test reports showed a bunch of errors on about 10% of the requests. Check out this report: Notice the Failed Request count. What the hey? Is WebAPI failing on roughly 10% of requests when sending JSON? Turns out: No it's not! But it took some sleuthing to figure out why it reports these failures. At first I thought that Web API was failing, and so to make sure I re-ran the test with Fiddler attached and runiisning the ab.exe test by using the -X switch: ab.exe -n100 -c10 -X localhost:8888 http://localhost/aspnetperf/api/HelloWorldJson which showed that indeed all requests where returning proper HTTP 200 results with full content. However ab.exe was reporting the errors. After some closer inspection it turned out that the dates varying in size altered the response length in dynamic output. For example: these two results: {"Id":10,"Name":"Rick","Entered":"2012-09-04T10:57:24.841926-10:00"} {"Id":10,"Name":"Rick","Entered":"2012-09-04T10:57:24.8519262-10:00"} are different in length for the number which results in 68 and 69 bytes respectively. The same URL produces different result lengths which is what ab.exe reports. I didn't notice at first bit the same is happening when running the ASHX handler with JSON.NET result since it uses the same serializer that varies the milliseconds. Moral: You can typically ignore Length failures in Apache Benchmark and when in doubt check the actual output with Fiddler. Note that the other failure values are accurate though. Another interesting Side Note: Perf drops over Time As I was running these tests repeatedly I was finding that performance steadily dropped from a startup peak to a 10-15% lower stable level. IOW, with Web API I'd start out with around 6500 req/sec and in subsequent runs it keeps dropping until it would stabalize somewhere around 5900 req/sec occasionally jumping lower. For these tests this is why I did the IIS RESET and warm up for individual tests. This is a little puzzling. Looking at Process Monitor while the test are running memory very quickly levels out as do handles and threads, on the first test run. Subsequent runs everything stays stable, but the performance starts going downwards. This applies to all the technologies - Handlers, Web Forms, MVC, Web API - curious to see if others test this and see similar results. Doing an IISRESET then resets everything and performance starts off at peak again… Summary As I stated at the outset, these were informal to satiate my curiosity not to prove that any technology is better or even faster than another. While there clearly are differences in performance the differences (other than WCF REST which was by far the slowest and the raw handler which was by far the highest) are relatively minor, so there is no need to feel that any one technology is a runaway standout in raw performance. Choosing a technology is about more than pure performance but also about the adequateness for the job and the easy of implementation. The strengths of each technology will make for any minor performance difference we see in these tests. However, to me it's important to get an occasional reality check and compare where new technologies are heading. Often times old stuff that's been optimized and designed for a time of less horse power can utterly blow the doors off newer tech and simple checks like this let you compare. Luckily we're seeing that much of the new stuff performs well even in V1.0 which is great. To me it was very interesting to see Web API perform relatively badly with plain string content, which originally led me to think that Web API might not be properly optimized just yet. For those that caught my Tweets late last week regarding WebAPI's slow responses was with String content which is in fact considerably slower. Luckily where it counts with serialized JSON and XML WebAPI actually performs better. But I do wonder what would make generic string content slower than serialized code? This stresses another point: Don't take a single test as the final gospel and don't extrapolate out from a single set of tests. Certainly Twitter can make you feel like a fool when you post something immediate that hasn't been fleshed out a little more <blush>. Egg on my face. As a result I ended up screwing around with this for a few hours today to compare different scenarios. Well worth the time… I hope you found this useful, if not for the results, maybe for the process of quickly testing a few requests for performance and charting out a comparison. Now onwards with more serious stuff… Resources Source Code on GitHub Apache HTTP Server Project (ab.exe is part of the binary distribution)© Rick Strahl, West Wind Technologies, 2005-2012Posted in ASP.NET  Web Api   Tweet !function(d,s,id){var js,fjs=d.getElementsByTagName(s)[0];if(!d.getElementById(id)){js=d.createElement(s);js.id=id;js.src="//platform.twitter.com/widgets.js";fjs.parentNode.insertBefore(js,fjs);}}(document,"script","twitter-wjs"); (function() { var po = document.createElement('script'); po.type = 'text/javascript'; po.async = true; po.src = 'https://apis.google.com/js/plusone.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(po, s); })();

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  • Developing Spring Portlet for use inside Weblogic Portal / Webcenter Portal

    - by Murali Veligeti
    We need to understand the main difference between portlet workflow and servlet workflow.The main difference between portlet workflow and servlet workflow is that, the request to the portlet can have two distinct phases: 1) Action phase 2) Render phase. The Action phase is executed only once and is where any 'backend' changes or actions occur, such as making changes in a database. The Render phase then produces what is displayed to the user each time the display is refreshed. The critical point here is that for a single overall request, the action phase is executed only once, but the render phase may be executed multiple times. This provides a clean separation between the activities that modify the persistent state of your system and the activities that generate what is displayed to the user.The dual phases of portlet requests are one of the real strengths of the JSR-168 specification. For example, dynamic search results can be updated routinely on the display without the user explicitly re-running the search. Most other portlet MVC frameworks attempt to completely hide the two phases from the developer and make it look as much like traditional servlet development as possible - we think this approach removes one of the main benefits of using portlets. So, the separation of the two phases is preserved throughout the Spring Portlet MVC framework. The primary manifestation of this approach is that where the servlet version of the MVC classes will have one method that deals with the request, the portlet version of the MVC classes will have two methods that deal with the request: one for the action phase and one for the render phase. For example, where the servlet version of AbstractController has the handleRequestInternal(..) method, the portlet version of AbstractController has handleActionRequestInternal(..) and handleRenderRequestInternal(..) methods.The Spring Portlet Framework is designed around a DispatcherPortlet that dispatches requests to handlers, with configurable handler mappings and view resolution, just as the DispatcherServlet in the Spring Web Framework does.  Developing portlet.xml Let's start the sample development by creating the portlet.xml file in the /WebContent/WEB-INF/ folder as shown below: <?xml version="1.0" encoding="UTF-8"?> <portlet-app version="2.0" xmlns="http://java.sun.com/xml/ns/portlet/portlet-app_2_0.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"> <portlet> <portlet-name>SpringPortletName</portlet-name> <portlet-class>org.springframework.web.portlet.DispatcherPortlet</portlet-class> <supports> <mime-type>text/html</mime-type> <portlet-mode>view</portlet-mode> </supports> <portlet-info> <title>SpringPortlet</title> </portlet-info> </portlet> </portlet-app> DispatcherPortlet is responsible for handling every client request. When it receives a request, it finds out which Controller class should be used for handling this request, and then it calls its handleActionRequest() or handleRenderRequest() method based on the request processing phase. The Controller class executes business logic and returns a View name that should be used for rendering markup to the user. The DispatcherPortlet then forwards control to that View for actual markup generation. As you can see, DispatcherPortlet is the central dispatcher for use within Spring Portlet MVC Framework. Note that your portlet application can define more than one DispatcherPortlet. If it does so, then each of these portlets operates its own namespace, loading its application context and handler mapping. The DispatcherPortlet is also responsible for loading application context (Spring configuration file) for this portlet. First, it tries to check the value of the configLocation portlet initialization parameter. If that parameter is not specified, it takes the portlet name (that is, the value of the <portlet-name> element), appends "-portlet.xml" to it, and tries to load that file from the /WEB-INF folder. In the portlet.xml file, we did not specify the configLocation initialization parameter, so let's create SpringPortletName-portlet.xml file in the next section. Developing SpringPortletName-portlet.xml Create the SpringPortletName-portlet.xml file in the /WebContent/WEB-INF folder of your application as shown below: <?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.0.xsd"> <bean id="viewResolver" class="org.springframework.web.servlet.view.InternalResourceViewResolver"> <property name="viewClass" value="org.springframework.web.servlet.view.JstlView"/> <property name="prefix" value="/jsp/"/> <property name="suffix" value=".jsp"/> </bean> <bean id="pointManager" class="com.wlp.spring.bo.internal.PointManagerImpl"> <property name="users"> <list> <ref bean="point1"/> <ref bean="point2"/> <ref bean="point3"/> <ref bean="point4"/> </list> </property> </bean> <bean id="point1" class="com.wlp.spring.bean.User"> <property name="name" value="Murali"/> <property name="points" value="6"/> </bean> <bean id="point2" class="com.wlp.spring.bean.User"> <property name="name" value="Sai"/> <property name="points" value="13"/> </bean> <bean id="point3" class="com.wlp.spring.bean.User"> <property name="name" value="Rama"/> <property name="points" value="43"/> </bean> <bean id="point4" class="com.wlp.spring.bean.User"> <property name="name" value="Krishna"/> <property name="points" value="23"/> </bean> <bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource"> <property name="basename" value="messages"/> </bean> <bean name="/users.htm" id="userController" class="com.wlp.spring.controller.UserController"> <property name="pointManager" ref="pointManager"/> </bean> <bean name="/pointincrease.htm" id="pointIncreaseController" class="com.wlp.spring.controller.IncreasePointsFormController"> <property name="sessionForm" value="true"/> <property name="pointManager" ref="pointManager"/> <property name="commandName" value="pointIncrease"/> <property name="commandClass" value="com.wlp.spring.bean.PointIncrease"/> <property name="formView" value="pointincrease"/> <property name="successView" value="users"/> </bean> <bean id="parameterMappingInterceptor" class="org.springframework.web.portlet.handler.ParameterMappingInterceptor" /> <bean id="portletModeParameterHandlerMapping" class="org.springframework.web.portlet.handler.PortletModeParameterHandlerMapping"> <property name="order" value="1" /> <property name="interceptors"> <list> <ref bean="parameterMappingInterceptor" /> </list> </property> <property name="portletModeParameterMap"> <map> <entry key="view"> <map> <entry key="pointincrease"> <ref bean="pointIncreaseController" /> </entry> <entry key="users"> <ref bean="userController" /> </entry> </map> </entry> </map> </property> </bean> <bean id="portletModeHandlerMapping" class="org.springframework.web.portlet.handler.PortletModeHandlerMapping"> <property name="order" value="2" /> <property name="portletModeMap"> <map> <entry key="view"> <ref bean="userController" /> </entry> </map> </property> </bean> </beans> The SpringPortletName-portlet.xml file is an application context file for your MVC portlet. It has a couple of bean definitions: viewController. At this point, remember that the viewController bean definition points to the com.ibm.developerworks.springmvc.ViewController.java class. portletModeHandlerMapping. As we discussed in the last section, whenever DispatcherPortlet gets a client request, it tries to find a suitable Controller class for handling that request. That is where PortletModeHandlerMapping comes into the picture. The PortletModeHandlerMapping class is a simple implementation of the HandlerMapping interface and is used by DispatcherPortlet to find a suitable Controller for every request. The PortletModeHandlerMapping class uses Portlet mode for the current request to find a suitable Controller class to use for handling the request. The portletModeMap property of portletModeHandlerMapping bean is the place where we map the Portlet mode name against the Controller class. In the sample code, we show that viewController is responsible for handling View mode requests. Developing UserController.java In the preceding section, you learned that the viewController bean is responsible for handling all the View mode requests. Your next step is to create the UserController.java class as shown below: public class UserController extends AbstractController { private PointManager pointManager; public void handleActionRequest(ActionRequest request, ActionResponse response) throws Exception { } public ModelAndView handleRenderRequest(RenderRequest request, RenderResponse response) throws ServletException, IOException { String now = (new java.util.Date()).toString(); Map<String, Object> myModel = new HashMap<String, Object>(); myModel.put("now", now); myModel.put("users", this.pointManager.getUsers()); return new ModelAndView("users", "model", myModel); } public void setPointManager(PointManager pointManager) { this.pointManager = pointManager; } } Every controller class in Spring Portlet MVC Framework must implement the org.springframework.web. portlet.mvc.Controller interface directly or indirectly. To make things easier, Spring Framework provides AbstractController class, which is the default implementation of the Controller interface. As a developer, you should always extend your controller from either AbstractController or one of its more specific subclasses. Any implementation of the Controller class should be reusable, thread-safe, and capable of handling multiple requests throughout the lifecycle of the portlet. In the sample code, we create the ViewController class by extending it from AbstractController. Because we don't want to do any action processing in the HelloSpringPortletMVC portlet, we override only the handleRenderRequest() method of AbstractController. Now, the only thing that HelloWorldPortletMVC should do is render the markup of View.jsp to the user when it receives a user request to do so. To do that, return the object of ModelAndView with a value of view equal to View. Developing web.xml According to Portlet Specification 1.0, every portlet application is also a Servlet Specification 2.3-compliant Web application, and it needs a Web application deployment descriptor (that is, web.xml). Let’s create the web.xml file in the /WEB-INF/ folder as shown in listing 4. Follow these steps: Open the existing web.xml file located at /WebContent/WEB-INF/web.xml. Replace the contents of this file with the code as shown below: <servlet> <servlet-name>ViewRendererServlet</servlet-name> <servlet-class>org.springframework.web.servlet.ViewRendererServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>ViewRendererServlet</servlet-name> <url-pattern>/WEB-INF/servlet/view</url-pattern> </servlet-mapping> <context-param> <param-name>contextConfigLocation</param-name> <param-value>/WEB-INF/applicationContext.xml</param-value> </context-param> <listener> <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class> </listener> The web.xml file for the sample portlet declares two things: ViewRendererServlet. The ViewRendererServlet is the bridge servlet for portlet support. During the render phase, DispatcherPortlet wraps PortletRequest into ServletRequest and forwards control to ViewRendererServlet for actual rendering. This process allows Spring Portlet MVC Framework to use the same View infrastructure as that of its servlet version, that is, Spring Web MVC Framework. ContextLoaderListener. The ContextLoaderListener class takes care of loading Web application context at the time of the Web application startup. The Web application context is shared by all the portlets in the portlet application. In case of duplicate bean definition, the bean definition in the portlet application context takes precedence over the Web application context. The ContextLoader class tries to read the value of the contextConfigLocation Web context parameter to find out the location of the context file. If the contextConfigLocation parameter is not set, then it uses the default value, which is /WEB-INF/applicationContext.xml, to load the context file. The Portlet Controller interface requires two methods that handle the two phases of a portlet request: the action request and the render request. The action phase should be capable of handling an action request and the render phase should be capable of handling a render request and returning an appropriate model and view. While the Controller interface is quite abstract, Spring Portlet MVC offers a lot of controllers that already contain a lot of the functionality you might need – most of these are very similar to controllers from Spring Web MVC. The Controller interface just defines the most common functionality required of every controller - handling an action request, handling a render request, and returning a model and a view. How rendering works As you know, when the user tries to access a page with PointSystemPortletMVC portlet on it or when the user performs some action on any other portlet on that page or tries to refresh that page, a render request is sent to the PointSystemPortletMVC portlet. In the sample code, because DispatcherPortlet is the main portlet class, Weblogic Portal / Webcenter Portal calls its render() method and then the following sequence of events occurs: The render() method of DispatcherPortlet calls the doDispatch() method, which in turn calls the doRender() method. After the doRenderService() method gets control, first it tries to find out the locale of the request by calling the PortletRequest.getLocale() method. This locale is used while making all the locale-related decisions for choices such as which resource bundle should be loaded or which JSP should be displayed to the user based on the locale. After that, the doRenderService() method starts iterating through all the HandlerMapping classes configured for this portlet, calling their getHandler() method to identify the appropriate Controller for handling this request. In the sample code, we have configured only PortletModeHandlerMapping as a HandlerMapping class. The PortletModeHandlerMapping class reads the value of the current portlet mode, and based on that, it finds out, the Controller class that should be used to handle this request. In the sample code, ViewController is configured to handle the View mode request so that the PortletModeHandlerMapping class returns the object of ViewController. After the object of ViewController is returned, the doRenderService() method calls its handleRenderRequestInternal() method. Implementation of the handleRenderRequestInternal() method in ViewController.java is very simple. It logs a message saying that it got control, and then it creates an instance of ModelAndView with a value equal to View and returns it to DispatcherPortlet. After control returns to doRenderService(), the next task is to figure out how to render View. For that, DispatcherPortlet starts iterating through all the ViewResolvers configured in your portlet application, calling their resolveViewName() method. In the sample code we have configured only one ViewResolver, InternalResourceViewResolver. When its resolveViewName() method is called with viewName, it tries to add /WEB-INF/jsp as a prefix to the view name and to add JSP as a suffix. And it checks if /WEB-INF/jsp/View.jsp exists. If it does exist, it returns the object of JstlView wrapping View.jsp. After control is returned to the doRenderService() method, it creates the object PortletRequestDispatcher, which points to /WEB-INF/servlet/view – that is, ViewRendererServlet. Then it sets the object of JstlView in the request and dispatches the request to ViewRendererServlet. After ViewRendererServlet gets control, it reads the JstlView object from the request attribute and creates another RequestDispatcher pointing to the /WEB-INF/jsp/View.jsp URL and passes control to it for actual markup generation. The markup generated by View.jsp is returned to user. At this point, you may question the need for ViewRendererServlet. Why can't DispatcherPortlet directly forward control to View.jsp? Adding ViewRendererServlet in between allows Spring Portlet MVC Framework to reuse the existing View infrastructure. You may appreciate this more when we discuss how easy it is to integrate Apache Tiles Framework with your Spring Portlet MVC Framework. The attached project SpringPortlet.zip should be used to import the project in to your OEPE Workspace. SpringPortlet_Jars.zip contains jar files required for the application. Project is written on Spring 2.5.  The same JSR 168 portlet should work on Webcenter Portal as well.  Downloads: Download WeblogicPotal Project which consists of Spring Portlet. Download Spring Jars In-addition to above you need to download Spring.jar (Spring2.5)

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  • Syncing Data with a Server using Silverlight and HTTP Polling Duplex

    - by dwahlin
    Many applications have the need to stay in-sync with data provided by a service. Although web applications typically rely on standard polling techniques to check if data has changed, Silverlight provides several interesting options for keeping an application in-sync that rely on server “push” technologies. A few years back I wrote several blog posts covering different “push” technologies available in Silverlight that rely on sockets or HTTP Polling Duplex. We recently had a project that looked like it could benefit from pushing data from a server to one or more clients so I thought I’d revisit the subject and provide some updates to the original code posted. If you’ve worked with AJAX before in Web applications then you know that until browsers fully support web sockets or other duplex (bi-directional communication) technologies that it’s difficult to keep applications in-sync with a server without relying on polling. The problem with polling is that you have to check for changes on the server on a timed-basis which can often be wasteful and take up unnecessary resources. With server “push” technologies, data can be pushed from the server to the client as it changes. Once the data is received, the client can update the user interface as appropriate. Using “push” technologies allows the client to listen for changes from the data but stay 100% focused on client activities as opposed to worrying about polling and asking the server if anything has changed. Silverlight provides several options for pushing data from a server to a client including sockets, TCP bindings and HTTP Polling Duplex.  Each has its own strengths and weaknesses as far as performance and setup work with HTTP Polling Duplex arguably being the easiest to setup and get going.  In this article I’ll demonstrate how HTTP Polling Duplex can be used in Silverlight 4 applications to push data and show how you can create a WCF server that provides an HTTP Polling Duplex binding that a Silverlight client can consume.   What is HTTP Polling Duplex? Technologies that allow data to be pushed from a server to a client rely on duplex functionality. Duplex (or bi-directional) communication allows data to be passed in both directions.  A client can call a service and the server can call the client. HTTP Polling Duplex (as its name implies) allows a server to communicate with a client without forcing the client to constantly poll the server. It has the benefit of being able to run on port 80 making setup a breeze compared to the other options which require specific ports to be used and cross-domain policy files to be exposed on port 943 (as with sockets and TCP bindings). Having said that, if you’re looking for the best speed possible then sockets and TCP bindings are the way to go. But, they’re not the only game in town when it comes to duplex communication. The first time I heard about HTTP Polling Duplex (initially available in Silverlight 2) I wasn’t exactly sure how it was any better than standard polling used in AJAX applications. I read the Silverlight SDK, looked at various resources and generally found the following definition unhelpful as far as understanding the actual benefits that HTTP Polling Duplex provided: "The Silverlight client periodically polls the service on the network layer, and checks for any new messages that the service wants to send on the callback channel. The service queues all messages sent on the client callback channel and delivers them to the client when the client polls the service." Although the previous definition explained the overall process, it sounded as if standard polling was used. Fortunately, Microsoft’s Scott Guthrie provided me with a more clear definition several years back that explains the benefits provided by HTTP Polling Duplex quite well (used with his permission): "The [HTTP Polling Duplex] duplex support does use polling in the background to implement notifications – although the way it does it is different than manual polling. It initiates a network request, and then the request is effectively “put to sleep” waiting for the server to respond (it doesn’t come back immediately). The server then keeps the connection open but not active until it has something to send back (or the connection times out after 90 seconds – at which point the duplex client will connect again and wait). This way you are avoiding hitting the server repeatedly – but still get an immediate response when there is data to send." After hearing Scott’s definition the light bulb went on and it all made sense. A client makes a request to a server to check for changes, but instead of the request returning immediately, it parks itself on the server and waits for data. It’s kind of like waiting to pick up a pizza at the store. Instead of calling the store over and over to check the status, you sit in the store and wait until the pizza (the request data) is ready. Once it’s ready you take it back home (to the client). This technique provides a lot of efficiency gains over standard polling techniques even though it does use some polling of its own as a request is initially made from a client to a server. So how do you implement HTTP Polling Duplex in your Silverlight applications? Let’s take a look at the process by starting with the server. Creating an HTTP Polling Duplex WCF Service Creating a WCF service that exposes an HTTP Polling Duplex binding is straightforward as far as coding goes. Add some one way operations into an interface, create a client callback interface and you’re ready to go. The most challenging part comes into play when configuring the service to properly support the necessary binding and that’s more of a cut and paste operation once you know the configuration code to use. To create an HTTP Polling Duplex service you’ll need to expose server-side and client-side interfaces and reference the System.ServiceModel.PollingDuplex assembly (located at C:\Program Files (x86)\Microsoft SDKs\Silverlight\v4.0\Libraries\Server on my machine) in the server project. For the demo application I upgraded a basketball simulation service to support the latest polling duplex assemblies. The service simulates a simple basketball game using a Game class and pushes information about the game such as score, fouls, shots and more to the client as the game changes over time. Before jumping too far into the game push service, it’s important to discuss two interfaces used by the service to communicate in a bi-directional manner. The first is called IGameStreamService and defines the methods/operations that the client can call on the server (see Listing 1). The second is IGameStreamClient which defines the callback methods that a server can use to communicate with a client (see Listing 2).   [ServiceContract(Namespace = "Silverlight", CallbackContract = typeof(IGameStreamClient))] public interface IGameStreamService { [OperationContract(IsOneWay = true)] void GetTeamData(); } Listing 1. The IGameStreamService interface defines server operations that can be called on the server.   [ServiceContract] public interface IGameStreamClient { [OperationContract(IsOneWay = true)] void ReceiveTeamData(List<Team> teamData); [OperationContract(IsOneWay = true, AsyncPattern=true)] IAsyncResult BeginReceiveGameData(GameData gameData, AsyncCallback callback, object state); void EndReceiveGameData(IAsyncResult result); } Listing 2. The IGameStreamClient interfaces defines client operations that a server can call.   The IGameStreamService interface is decorated with the standard ServiceContract attribute but also contains a value for the CallbackContract property.  This property is used to define the interface that the client will expose (IGameStreamClient in this example) and use to receive data pushed from the service. Notice that each OperationContract attribute in both interfaces sets the IsOneWay property to true. This means that the operation can be called and passed data as appropriate, however, no data will be passed back. Instead, data will be pushed back to the client as it’s available.  Looking through the IGameStreamService interface you can see that the client can request team data whereas the IGameStreamClient interface allows team and game data to be received by the client. One interesting point about the IGameStreamClient interface is the inclusion of the AsyncPattern property on the BeginReceiveGameData operation. I initially created this operation as a standard one way operation and it worked most of the time. However, as I disconnected clients and reconnected new ones game data wasn’t being passed properly. After researching the problem more I realized that because the service could take up to 7 seconds to return game data, things were getting hung up. By setting the AsyncPattern property to true on the BeginReceivedGameData operation and providing a corresponding EndReceiveGameData operation I was able to get around this problem and get everything running properly. I’ll provide more details on the implementation of these two methods later in this post. Once the interfaces were created I moved on to the game service class. The first order of business was to create a class that implemented the IGameStreamService interface. Since the service can be used by multiple clients wanting game data I added the ServiceBehavior attribute to the class definition so that I could set its InstanceContextMode to InstanceContextMode.Single (in effect creating a Singleton service object). Listing 3 shows the game service class as well as its fields and constructor.   [ServiceBehavior(ConcurrencyMode = ConcurrencyMode.Multiple, InstanceContextMode = InstanceContextMode.Single)] public class GameStreamService : IGameStreamService { object _Key = new object(); Game _Game = null; Timer _Timer = null; Random _Random = null; Dictionary<string, IGameStreamClient> _ClientCallbacks = new Dictionary<string, IGameStreamClient>(); static AsyncCallback _ReceiveGameDataCompleted = new AsyncCallback(ReceiveGameDataCompleted); public GameStreamService() { _Game = new Game(); _Timer = new Timer { Enabled = false, Interval = 2000, AutoReset = true }; _Timer.Elapsed += new ElapsedEventHandler(_Timer_Elapsed); _Timer.Start(); _Random = new Random(); }} Listing 3. The GameStreamService implements the IGameStreamService interface which defines a callback contract that allows the service class to push data back to the client. By implementing the IGameStreamService interface, GameStreamService must supply a GetTeamData() method which is responsible for supplying information about the teams that are playing as well as individual players.  GetTeamData() also acts as a client subscription method that tracks clients wanting to receive game data.  Listing 4 shows the GetTeamData() method. public void GetTeamData() { //Get client callback channel var context = OperationContext.Current; var sessionID = context.SessionId; var currClient = context.GetCallbackChannel<IGameStreamClient>(); context.Channel.Faulted += Disconnect; context.Channel.Closed += Disconnect; IGameStreamClient client; if (!_ClientCallbacks.TryGetValue(sessionID, out client)) { lock (_Key) { _ClientCallbacks[sessionID] = currClient; } } currClient.ReceiveTeamData(_Game.GetTeamData()); //Start timer which when fired sends updated score information to client if (!_Timer.Enabled) { _Timer.Enabled = true; } } Listing 4. The GetTeamData() method subscribes a given client to the game service and returns. The key the line of code in the GetTeamData() method is the call to GetCallbackChannel<IGameStreamClient>().  This method is responsible for accessing the calling client’s callback channel. The callback channel is defined by the IGameStreamClient interface shown earlier in Listing 2 and used by the server to communicate with the client. Before passing team data back to the client, GetTeamData() grabs the client’s session ID and checks if it already exists in the _ClientCallbacks dictionary object used to track clients wanting callbacks from the server. If the client doesn’t exist it adds it into the collection. It then pushes team data from the Game class back to the client by calling ReceiveTeamData().  Since the service simulates a basketball game, a timer is then started if it’s not already enabled which is then used to randomly send data to the client. When the timer fires, game data is pushed down to the client. Listing 5 shows the _Timer_Elapsed() method that is called when the timer fires as well as the SendGameData() method used to send data to the client. void _Timer_Elapsed(object sender, ElapsedEventArgs e) { int interval = _Random.Next(3000, 7000); lock (_Key) { _Timer.Interval = interval; _Timer.Enabled = false; } SendGameData(_Game.GetGameData()); } private void SendGameData(GameData gameData) { var cbs = _ClientCallbacks.Where(cb => ((IContextChannel)cb.Value).State == CommunicationState.Opened); for (int i = 0; i < cbs.Count(); i++) { var cb = cbs.ElementAt(i).Value; try { cb.BeginReceiveGameData(gameData, _ReceiveGameDataCompleted, cb); } catch (TimeoutException texp) { //Log timeout error } catch (CommunicationException cexp) { //Log communication error } } lock (_Key) _Timer.Enabled = true; } private static void ReceiveGameDataCompleted(IAsyncResult result) { try { ((IGameStreamClient)(result.AsyncState)).EndReceiveGameData(result); } catch (CommunicationException) { // empty } catch (TimeoutException) { // empty } } LIsting 5. _Timer_Elapsed is used to simulate time in a basketball game. When _Timer_Elapsed() fires the SendGameData() method is called which iterates through the clients wanting to be notified of changes. As each client is identified, their respective BeginReceiveGameData() method is called which ultimately pushes game data down to the client. Recall that this method was defined in the client callback interface named IGameStreamClient shown earlier in Listing 2. Notice that BeginReceiveGameData() accepts _ReceiveGameDataCompleted as its second parameter (an AsyncCallback delegate defined in the service class) and passes the client callback as the third parameter. The initial version of the sample application had a standard ReceiveGameData() method in the client callback interface. However, sometimes the client callbacks would work properly and sometimes they wouldn’t which was a little baffling at first glance. After some investigation I realized that I needed to implement an asynchronous pattern for client callbacks to work properly since 3 – 7 second delays are occurring as a result of the timer. Once I added the BeginReceiveGameData() and ReceiveGameDataCompleted() methods everything worked properly since each call was handled in an asynchronous manner. The final task that had to be completed to get the server working properly with HTTP Polling Duplex was adding configuration code into web.config. In the interest of brevity I won’t post all of the code here since the sample application includes everything you need. However, Listing 6 shows the key configuration code to handle creating a custom binding named pollingDuplexBinding and associate it with the service’s endpoint.   <bindings> <customBinding> <binding name="pollingDuplexBinding"> <binaryMessageEncoding /> <pollingDuplex maxPendingSessions="2147483647" maxPendingMessagesPerSession="2147483647" inactivityTimeout="02:00:00" serverPollTimeout="00:05:00"/> <httpTransport /> </binding> </customBinding> </bindings> <services> <service name="GameService.GameStreamService" behaviorConfiguration="GameStreamServiceBehavior"> <endpoint address="" binding="customBinding" bindingConfiguration="pollingDuplexBinding" contract="GameService.IGameStreamService"/> <endpoint address="mex" binding="mexHttpBinding" contract="IMetadataExchange" /> </service> </services>   Listing 6. Configuring an HTTP Polling Duplex binding in web.config and associating an endpoint with it. Calling the Service and Receiving “Pushed” Data Calling the service and handling data that is pushed from the server is a simple and straightforward process in Silverlight. Since the service is configured with a MEX endpoint and exposes a WSDL file, you can right-click on the Silverlight project and select the standard Add Service Reference item. After the web service proxy is created you may notice that the ServiceReferences.ClientConfig file only contains an empty configuration element instead of the normal configuration elements created when creating a standard WCF proxy. You can certainly update the file if you want to read from it at runtime but for the sample application I fed the service URI directly to the service proxy as shown next: var address = new EndpointAddress("http://localhost.:5661/GameStreamService.svc"); var binding = new PollingDuplexHttpBinding(); _Proxy = new GameStreamServiceClient(binding, address); _Proxy.ReceiveTeamDataReceived += _Proxy_ReceiveTeamDataReceived; _Proxy.ReceiveGameDataReceived += _Proxy_ReceiveGameDataReceived; _Proxy.GetTeamDataAsync(); This code creates the proxy and passes the endpoint address and binding to use to its constructor. It then wires the different receive events to callback methods and calls GetTeamDataAsync().  Calling GetTeamDataAsync() causes the server to store the client in the server-side dictionary collection mentioned earlier so that it can receive data that is pushed.  As the server-side timer fires and game data is pushed to the client, the user interface is updated as shown in Listing 7. Listing 8 shows the _Proxy_ReceiveGameDataReceived() method responsible for handling the data and calling UpdateGameData() to process it.   Listing 7. The Silverlight interface. Game data is pushed from the server to the client using HTTP Polling Duplex. void _Proxy_ReceiveGameDataReceived(object sender, ReceiveGameDataReceivedEventArgs e) { UpdateGameData(e.gameData); } private void UpdateGameData(GameData gameData) { //Update Score this.tbTeam1Score.Text = gameData.Team1Score.ToString(); this.tbTeam2Score.Text = gameData.Team2Score.ToString(); //Update ball visibility if (gameData.Action != ActionsEnum.Foul) { if (tbTeam1.Text == gameData.TeamOnOffense) { AnimateBall(this.BB1, this.BB2); } else //Team 2 { AnimateBall(this.BB2, this.BB1); } } if (this.lbActions.Items.Count > 9) this.lbActions.Items.Clear(); this.lbActions.Items.Add(gameData.LastAction); if (this.lbActions.Visibility == Visibility.Collapsed) this.lbActions.Visibility = Visibility.Visible; } private void AnimateBall(Image onBall, Image offBall) { this.FadeIn.Stop(); Storyboard.SetTarget(this.FadeInAnimation, onBall); Storyboard.SetTarget(this.FadeOutAnimation, offBall); this.FadeIn.Begin(); } Listing 8. As the server pushes game data, the client’s _Proxy_ReceiveGameDataReceived() method is called to process the data. In a real-life application I’d go with a ViewModel class to handle retrieving team data, setup data bindings and handle data that is pushed from the server. However, for the sample application I wanted to focus on HTTP Polling Duplex and keep things as simple as possible.   Summary Silverlight supports three options when duplex communication is required in an application including TCP bindins, sockets and HTTP Polling Duplex. In this post you’ve seen how HTTP Polling Duplex interfaces can be created and implemented on the server as well as how they can be consumed by a Silverlight client. HTTP Polling Duplex provides a nice way to “push” data from a server while still allowing the data to flow over port 80 or another port of your choice.   Sample Application Download

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