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  • NServiceBus Generic Host and mqsvc.exe high CPU

    - by Michael Stephenson
    We have been doing some work with NServiceBus recently and observed some unusual behaviour which was caused by our mistake and seemed worthy of a small post.   The Scenario In our solution we were doing some standard NServiceBus stuff by pushing a message to a queue using NServiceBus.  We had a direct send/receive scenario rather than a publish/subscribe one.   The background process which was meant to collect the message and then process it was a normal NServiceBus message handler.  We would run the NServiceBus.Host.exe which would find the handler and then do the usual NServiceBus magic.   The Problem In this solution we were creating some automated tests around this module of the integration process to ensure that it would work well.  We had two tests.   Test 1 This test would start NServiceBus.Host.exe using the Process object, then seed a message to the queue via our web service façade sitting above the queue which wrapped NServiceBus.  The background process would then process the message and the test would check the message had been processed fine.   If all was well then the NServiceBus.Host.exe process was stopped.   Test 2 In test 2 we would do a very similar thing except that instead of starting the process the test would install NServiceBus.Host.exe as a windows service and then start the service before the test and once the test was executed it would stop the test.   The Results of the Tests Test 1 worked really well, however in test 2 we found that it didn’t really work at all, instead of doing the background process we were finding that between mqsvc.exe and NServiceBus.Host.exe the CPU on the machine was maxed and nothing was really happening.   The Solution After trying a few things we found it was the permissions on the queue were not set correctly.  Once this was resolved it all worked fine and CPU was not excessive and ran just like the console application.   I think the couple of take aways from this are:   Make sure you set the windows service for NserviceBus Generic Host to the right credentials When you install the generic host as a windows service then by default it will use the default windows credentials.  For any production like scenario you should be using a domain account to run the process as via the windows service. Make sure you have the queue set with the right permissions For the credentials you have used to configure the generic host as a windows service you should ensure that this user has the appropriate permissions for any queues it will interact with. Make sure you turn on the right logging configuration in NServiceBus When this wasnt working correctly we didnt know there was an issue, we were just experiencing the high CPU condition.  I am a little surprised that there wasnt something logged and that the process didnt crash.  I guess this could be by design bearing in mind that the process could be monitoring many queues.  In this point Im just saying that originally we didnt have all of the log4net logging which is available from NServiceBus turned on.  Its probably a good idea to have this turned on and configured until you are happy your solution is working fine.   Thanks to Ahmed Hashmi on my team who got this working in the end.

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  • Using NServiceBus behind a custom web service

    - by Michael Stephenson
    In this post I'd like to talk about an architecture scenario we had recently and how we were able to utilise NServiceBus to help us address this problem. Scenario Cognos is a reporting system used by one of my clients. A while back we developed a web service façade to allow line of business applications to be able to access reports from Cognos to support their various functions. The service was intended to provide access to reports which were quick running reports or pre-generated reports which could be accessed real-time on demand. One of the key aims of the web service was to provide a simple generic interface to allow applications to get any report without needing to worry about the complex .net SDK for Cognos. The web service also supported multi-hop kerberos delegation so that report data could be accesses under the context of the end user. This service was working well for a period of time. The Problem The problem we encountered was that reports were now also required to be available to batch processes. The original design was optimised for low latency so users would enjoy a positive experience, however when the batch processes started to request 250+ concurrent reports over an extended period of time you can begin to imagine the sorts of problems that come into play. The key problems this new scenario caused are: Users may be affected and the latency of on demand reports was significantly slower The Cognos infrastructure was not scaled sufficiently to be able to cope with these long peaks of load From a cost perspective it just isn't feasible to scale the Cognos infrastructure to be able to handle the load when it is only for a couple of hour window each night. We really needed to introduce a second pattern for accessing this service which would support high through-put scenarios. We also had little control over the batch process in terms of being able to throttle its load. We could however make some changes to the way it accessed the reports. The Approach My idea was to introduce a throttling mechanism between the Web Service Façade and Cognos. This would allow the batch processes to push reports requests hard at the web service which we were confident the web service can handle. The web service would then queue these requests and process them behind the scenes and make a call back to the batch application to provide the report once it had been accessed. In terms of technology we had some limitations because we were not able to use WCF or IIS7 where the MSMQ-Activated WCF services could have helped, but we did have MSMQ as an option and I thought NServiceBus could do just the job to help us here. The flow of how this would work was as follows: The batch applications would send a request for a report to the web service The web service uses NServiceBus to send the message to a Queue The NServiceBus Generic Host is running as a windows service with a message handler which subscribes to these messages The message handler gets the message, accesses the report from Cognos The message handler calls back to the original batch application, this is decoupled because the calling application provides a call back url The report gets into the batch application and is processed as normal This approach looks something like the below diagram: The key points are an application wanting to take advantage of the batch driven reports needs to do the following: Implement our call back contract Make a call to the service providing a call back url Provide a correlation ID so it knows how to tie each response back to its request What does NServiceBus offer in this solution So this scenario is not the typical messaging service bus type of solution people implement with NServiceBus, but it did offer the following: Simplified interaction with MSMQ Offered the ability to configure the number of processes working through the queue so we could find a balance between load on Cognos versus the applications end to end processing time NServiceBus offers retries and a way to manage failed messages NServiceBus offers a high availability setup The simple thing is that NServiceBus gave us the platform to build the solution on. We just implemented a message handler which functionally processed a message and we could rely on NServiceBus to do all of the hard work around managing the queues and all of the lower level things that would have took ages to write to any kind of robust level. Conclusion With this approach we were able to deal with a fairly significant performance issue with out too much rework. Hopefully this write up gives people some insight into ideas on how to leverage the excellent NServiceBus framework to help solve integration and high through-put scenarios.

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  • Hello World - My Name is Christian Finn and I'm a WebCenter Evangelist

    - by Michael Snow
    12.00 Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Cambria","serif"; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin;}  Good Morning World! I'd like to introduce a new member of the Oracle WebCenter Team, Christian Finn. We decided to let him do his own intros today. Look for his guest posts next week and he'll be a frequent contributor to WebCenter blog and voice of the community. Hello (Oracle) World! Hi everyone, my name is Christian Finn. It’s a coder’s tradition to have “hello world” be the first output from a new program or in a new language. While I have left my coding days far behind, it still seems fitting to start my new role here at Oracle by saying hello to all of you—our customers, partners and my colleagues. So by way of introduction, a little background about me. I am the new senior director for evangelism on the WebCenter product management team. Not only am I new to Oracle, but the evangelism team is also brand new. Our mission is to raise the profile of Oracle in all of the markets/conversations in which WebCenter competes—social business, collaboration, portals, Internet sites, and customer/audience engagement. This is all pretty familiar turf for me because, as some of you may know, until recently I was the director of product management at Microsoft for Microsoft SharePoint Server and several other SharePoint products. And prior to that, I held management roles at Microsoft in marketing, channels, learning, and enterprise sales. Before Microsoft, I got my start in the industry as a software trainer and Lotus Notes consultant. I am incredibly excited to be joining Oracle at this time because of the tremendous opportunity that lies ahead to improve how people and businesses work. Of all the vendors offering a vision for social business, Oracle is unique in having best of breed strength in market (or coming soon) in all three critical areas: customer experience management; the middleware and back-end applications that run your business; and in the social, collaboration, and content technologies that are the connective tissue between them. Everyone else can offer one or two of the above, but not all three unified together. So it is a great time to come board and there’s a fantastic team of people hard at work on building great products for you. In the coming weeks and months you’ll be hearing much more from us. For now, we’ll kick things off with some blog posts here on the WebCenter blog. Enjoy the reads and please share your thoughts with me over Twitter on @cfinn.

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  • C#: A "Dumbed-Down" C++?

    - by James Michael Hare
    I was spending a lovely day this last weekend watching my sons play outside in one of the better weekends we've had here in Saint Louis for quite some time, and whilst watching them and making sure no limbs were broken or eyes poked out with sticks and other various potential injuries, I was perusing (in the correct sense of the word) this month's MSDN magazine to get a sense of the latest VS2010 features in both IDE and in languages. When I got to the back pages, I saw a wonderful article by David S. Platt entitled, "In Praise of Dumbing Down"  (msdn.microsoft.com/en-us/magazine/ee336129.aspx).  The title captivated me and I read it and found myself agreeing with it completely especially as it related to my first post on divorcing C++ as my favorite language. Unfortunately, as Mr. Platt mentions, the term dumbing-down has negative connotations, but is really and truly a good thing.  You are, in essence, taking something that is extremely complex and reducing it to something that is much easier to use and far less error prone.  Adding safeties to power tools and anti-kick mechanisms to chainsaws are in some sense "dumbing them down" to the common user -- but that also makes them safer and more accessible for the common user.  This was exactly my point with C++ and C#.  I did not mean to infer that C++ was not a useful or good language, but that in a very high percentage of cases, is too complex and error prone for the job at hand. Choosing the correct programming language for a job is a lot like choosing any other tool for a task.  For example: if I want to dig a French drain in my lawn, I can attempt to use a huge tractor-like backhoe and the job would be done far quicker than if I would dig it by hand.  I can't deny that the backhoe has the raw power and speed to perform.  But you also cannot deny that my chances of injury or chances of severing utility lines or other resources climb at an exponential rate inverse to the amount of training I may have on that machinery. Is C++ a powerful tool?  Oh yes, and it's great for those tasks where speed and performance are paramount.  But for most of us, it's the wrong tool.  And keep in mind, I say this even though I have 17 years of experience in using it and feel myself highly adept in utilizing its features both in the standard libraries, the STL, and in supplemental libraries such as BOOST.  Which, although greatly help with adding powerful features quickly, do very little to curb the relative dangers of the language. So, you may say, the fault is in the developer, that if the developer had some higher skills or if we only hired C++ experts this would not be an issue.  Now, I will concede there is some truth to this.  Obviously, the higher skilled C++ developers you hire the better the chance they will produce highly performant and error-free code.  However, what good is that to the average developer who cannot afford a full stable of C++ experts? That's my point with C#:  It's like a kinder, gentler C++.  It gives you nearly the same speed, and in many ways even more power than C++, and it gives you a much softer cushion for novices to fall against if they code less-than-optimally.  A bug is a bug, of course, in any language, but C# does a good job of hiding and taking on the task of handling almost all of the resource issues that make C++ so tricky.  For my money, C# is much more maintainable, more feature-rich, second only slightly in performance, faster to market, and -- last but not least -- safer and easier to use.  That's why, where I work, I much prefer to see the developers moving to C#.  The quantity of bugs is much lower, and we don't need to hire "experts" to achieve the same results since the language itself handles those resource pitfalls so prevalent in poorly written C++ code.  C++ will still have its place in the world, and I'm sure I'll still use it now and again where it is truly the correct tool for the job, but for nearly every other project C# is a wonderfully "dumbed-down" version of C++ -- in the very best sense -- and to me, that's the smart choice.

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  • BizTalk Testing Series - The xpath Function

    - by Michael Stephenson
    Background While the xpath function in a BizTalk orchestration is a very powerful feature I have often come across the situation where someone has hard coded an xpath expression in an orchestration. If you have read some of my previous posts about testing I've tried to get across the general theme like test-driven or test-assisted development approaches where the underlying principle is that your building up your solution of small well tested units that are put together and the resulting solution is usually quite robust. You will be finding more bugs within your unit tests and fewer outside of your team. The thing I don't like about the xpath functions usual usage is when you come across an orchestration which has something like the below snippet in an expression or assign shape: string result = xpath(myMessage,"string(//Order/OrderItem/ProductName)"); My main issue with this is that the xpath statement is hard coded in the orchestration and you don't really know it works until you are running the orchestration. Some of the problems I think you end up with are: You waste time with lengthy debugging of the orchestration when your statement isn't working You might not know the function isn't working quite as expected because the testable unit around it is big You are much more open to regression issues if your schema changes     Approach to Testing The technique I usually follow is to hold the xpath statement as a constant in a helper class or to format a constant with a helper function to get the actual xpath statement. It is then used by the orchestration like follows. string result = xpath(myMessage, MyHelperClass.ProductNameXPathStatement); This means that because the xpath statement is available outside of the orchestration it now becomes testable in its own right. This means: I can test it in its own right I'm less likely to waste time tracking down problems caused by an error in the statement I can reduce the risk or regression issuess I'm now able to implement some testing around my xpath statements which usually are something like the following:    The test will use a sample xml file The sample will be validated against the schema The test will execute the xpath statement and then check the results are as expected     Walk-through BizTalk uses the XPathNavigator internally behind the xpath function to implement the queries you will usually use using the navigators select or evaluate functions. In the sample (link at bottom) I have a small solution which contains a schema from which I have generated a sample instance. I will then use this instance as the basis for my tests.     In the below diagram you can see the helper class which I've encapsulated my xpath expressions in, and some helper functions which will format the expression in the case of a repeating node which would want to inject an index into the xpath query.             I have then created a test class which has some functions to execute some queries against my sample xml file. An example of this is below.         In the test class I have a couple of helper functions which will execute the xpath expressions in a similar way to BizTalk. You could have a proper helper class to do this if you wanted.         You can see now in the BizTalk expression editor I can use these functions alongside the xpath function.         Conclusion I hope you can see with very little effort you can make your life much easier by testing xpath statements outside of an orchestration rather than using them directly hard coded into the orchestration.     This can also save you lots of pain longer term because your build should break if your schema changes unexpectedly causing these xpath tests to fail where as your tests around the orchestration will be more difficult to troubleshoot and workout the cause of the problem.     Sample Link The sample is available from the following link: http://code.msdn.microsoft.com/testbtsxpathfunction     Other Tools On the subject of using the xpath function, if you don't already use it the below tool is very useful for creating your xpath statements (thanks BizBert) http://www.bizbert.com/bizbert/2007/11/30/XPath+The+Hidden+Language+Of+BizTalk.aspx

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  • Oracle is #1 in Life Sciences!

    - by Michael Snow
    Guest post today by: John Klinke, Senior Principal Product Manager, Oracle WebCenter Content 12.00 Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Calibri","sans-serif"; mso-fareast-font-family:Calibri; mso-bidi-font-family:"Times New Roman";} Based on the announcement last week at EMC World about Documentum for Life Sciences, it looks like EMC is starting to have regrets about pulling out of the life sciences space over the last few years. Certainly their content management customers and partners in life sciences have noticed their retreat. Many of them are now talking to us about WebCenter Content since they’ve seen the writing on the wall regarding Documentum’s decline, including falling revenue, shrinking investment, departure of key executives, and EMC’s auditing of existing customers. While EMC has been neglecting the life sciences industry over the last few years, Oracle has been increasing its investment and commitment by providing best-of-breed solutions to enable pharmaceutical, medical device, biotech and CRO companies to improve productivity and drive innovation. As a result, according to IDC Health Insights, Oracle is #1 in life sciences. From research and development through clinical development and manufacturing to sales and marketing, Oracle provides the solutions that life sciences companies depend on to accelerate R&D, expedite clinical trials, and speed time to market. Specifically for Oracle WebCenter, our life sciences business is booming thanks to our comprehensive offerings led by Oracle WebCenter Content, our 21 CFR Part 11 compliant enterprise content management platform. Unlike Documentum, WebCenter Content is all about keeping the cost of ownership low - through simplicity, flexibility, and out-of-the-box integrations. WebCenter Content is a single, comprehensive ECM platform that can handle all your content management needs, from controlled documents to digital asset management, records management and document imaging and capture. And it is much more flexible, letting you do configuration changes instead of customizations to meet your business needs. It also saves you money by being pre-integrated with the rest of the Oracle Fusion Middleware technology stack and with leading enterprise applications like Siebel (including Siebel CTMS), Primavera, E-Business Suite, JD Edwards and PeopleSoft. So if you think EMC’s announcement last week was too little and too late, I’m happy to report that Oracle is here to help. Back in October, we announced our Move Off Documentum offer, which provides a 100% trade-in credit for your Documentum licenses when you purchase Oracle WebCenter, and the good news is, this offer is still available for a limited time. So stop maintaining Documentum and start innovating with Oracle WebCenter. For more details see www.oracle.com/moveoff/documentum.

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  • AccelerometerInput XNA GameComponent

    - by Michael B. McLaughlin
    Bad accelerometer controls kill otherwise good games. I decided to try to do something about it. So I create an XNA GameComponent called AccelerometerInput. It’s still a beta project but you are welcome to try it, use it, modify it, etc. I’m releasing under the terms of the Microsoft Public License. Important info: First, it only supports tilt-style controls currently. I have not implemented motion-style controls yet (and make no promises as to when I might find time to do so). Second, I commented it heavily so that you can (hopefully) understand what it is doing. Please read the comments and examine the sample game for a usage overview. There are configurable parameters which I encourage you to make use of (both by modifying the default values where your testing shows it to be appropriate and also by implementing a calibration mechanism in your game that lets the user adjust those configurable values based on his or her own circumstances). Third, even with this code, accelerometer controls are still a fairly advanced topic area; you will likely find nothing but disappointment if you simply plunk this into some project without testing it on a device (or preferably on several devices). Fourth, if you do try this code and find that something doesn’t work as expected on your phone, please let me know as I want to improve it and can only do so with your help. Let me know what phone model it is, what you tried doing, what you expected, and what result you had instead. I may or may not be able to incorporate it into the code, but I can let others know at the very least so that they can make appropriate modifications to their games (I’m hopeful that all phones are reasonably similar in their workings and require, at most, a slight calibration change, but I simply don’t know). Fifth, although I’ll do my best to answer any questions you may have about it, I’m very busy with a number of things currently so it might take a little while. Please look through the code and examine the comments and sample game first before asking any questions. It’s likely that the answer is in there. If not, or if you just aren’t really sure, ask away. Sixth, there are differences between a portrait-mode game and a landscape mode game (specifically in the appropriate default tilt adjustment for toward the user/away from the user calculations). This is documented and the default is set for landscape. If you use this for a portrait game, make the appropriate change (look for the TODO: comment in AccelerometerInput.cs). Seventh, no provision whatsoever is made for disabling screen locking. It is up to you to implement that and to take appropriate measures to detect when the user has been idle for too long and timeout the game. That code is very game-specific. If you have questions about such matters, consult the relevant MSDN documentation and, if you still have questions, visit the App Hub forums and ask there. I answer questions there a lot and so I may even stumble across your question and answer it. But that’s a much better forum than the comments section here for questions of that sort so I would appreciate it if you asked idle detection-related questions there (or on some other suitable site that you may be more familiar and comfortable with). Eighth, this is an XNA GameComponent intended for XNA-based games on WP7. A sufficiently knowledgeable Silverlight developer should have no problem adapting it for use in a Silverlight game or app. I may create a Silverlight version at some point myself. Right now I do not have the time, unfortunately. Ok. Without further ado: http://www.bobtacoindustries.com/developers/utils/AccelerometerInput.zip Have a great St. Patrick’s Day!

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  • Good Books About Scaling Up Databases/Servers/etc.?

    - by Mehrdad
    I've applied for an internship at a startup company that expects its user base to grow by a large factor in a small amount of time, and so part of their project is to scale everything up so that they're ready: handling more/larger requests efficiently, handling server failures, load balancing, getting more JavaScript to run faster on the client computers, etc. Part of my job will also be figuring out what to do, so it's not obvious what my exact task will be at the moment. I was told that I should start reading up a little more about this so that I would have a little bit of an idea of what to do. What are some good books for me to read on this topic? I have a little bit of experience with the usage of MySQL (and also a little experience with web development), but in no way do I claim any knowledge on the internal workings of databases or distributed systems, so I might need readings more on the introductory side.

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  • How to Force Aero Peek to Stay Up

    - by user26900
    Let's say I have a video running in an application. If I hover my mouse over the taskbar, it shows a little popup windows that diplays the video (aero peek). Sometimes I'm running a maximized window and I want to have this little screen always popped up. (Kind've like when your using the TV Guide menu, you still see a little clip of the video)

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  • DNS issue for internal website routing internet connection from remote location

    - by Michael Paul
    I have an issue that I could use some help with. Our company has a main location and a remote location. Previously, the remote location was connected to the main location through an internet connection VPN tunnel. The connection was pitifully slow at 1.5Mbps, so we upgraded it with a 75Mbps direct link. That meant the remote location lost it's internet access, so we routed their access through the main office internet connection. Everything works perfect except for one thing. The website we host is not accessible from the remote location unless the IP address is used. If I do NSLOOKUP on our website address from a machine connected to the main location network, it resolves correctly to the inside IP address. However, if I do the same from a remote location machine, it resolves to the website's outside IP address. Our internal DNS server(s) have a pointer and CNAME records set up, and everything was working perfectly before the connection was upgraded. In addition, the remote location has a domain controller, DNS server and DHCP server to service these requests at the remote location and prevent these requests from getting routed back and forth over the link. So I think was it happening is that for some reason the DNS server at the remote location is not resolving our website name correctly and passing the requests on to the routers, which then push the request out to the internet DNS system. That resolves the name to our external IP. This is purely a DNS issue, everything else works just fine. I am just stumped on this one. Any ideas on how to fix this? Edit: I forgot to mention that at the remote side of the link is a Cisco ASA-5505 and at the main office there is a Cisco ASA-5510. The link is connected between these 2 devices and the routing is handled in the 5510. Thanks, Michael

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  • no mails routed to/from new Exchange 2010

    - by Michael
    I have an Exchange Server 2003 up and running for years. Now I am in the mid of transition to Exchange Server 2010, I already installed it, put the latest Servicepack on it and everything seems fine, BUT: Mails do not get delivered to MailBoxes on the new Exchange 2010. e.g. when I create a new mailbox on the old server, Emails in and out to/from it work like a charm. But as soon as I move it to the new server, emails get stuck. Noe delivered from outside or old mailboxes, not send out from the new server to enywhere. Sending between Mailboxes on the new Server of course is working. I can see the connectors between old and new Server in the Exchange 2003 Admin Tool, but I cannot find these nowhere on the new server. I have also setup sending connectors at the new server to send out mails directly, but that does not work. In all other areas, the servers are perfectly working together - moving mailboxes between, seeing each other etc. "just" they dont exchange (!) any emails - Any ideas what I missed? I also followed the hints from: Upgrading from Exchange 2003 to Exchange 2010, routing works in one direction only There Emails were transported at least in one direction, in my case they are not transported at all. Both my connectors are up and valid abd have the correct source/target shown on Get-RoutingGroupConnector | FL Kind regards Michael

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  • Cannot connect to Windows SBS Essentials 2011

    - by Michael Ervin
    Using the Launchpad from the Mac, trying to connect to Server Essentials 2011, no one is able to actually log in. The little login wheel keeps spinning and spinning. Anyone have any ideas what might be keeping us from logging in? On the mac side, we are using 10.6 and 10.7, but both are exhibiting the same problem. I also cannot connect to the server by remote desktop connection within the local network. HELP!

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  • STOP 0x7b booting from iSCSI

    - by Michael
    Hi, I've a Windows 2008 SBS running. It boots of iSCSI. That setup worked for months until yesterday. I intended to reboot and gained a: STOP 0x0000007b INACCESSIBLE_BOOT_DEVICE and no idea why. My setup hasn't changed. No new controller, no new or changed iSCSI targets, no new Network Card or IP address changes. I had all Windows Updates on it. Last known good: same STOP. Allow unsigned drivers: same STOP. Safe mode (all variants): same STOP. Mount target from a client: works. Filesystem check fine. I booted of the SBS DVD but in computer repair options my target doesn't appear. When i choose setup the target appears. So, how can i diagnose what's going wrong? Any helpful tools? Any hints? Thanks in advance Michael

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  • Modularity through HTTP

    - by Michael Williamson
    As programmers, we strive for modularity in the code we write. We hope that splitting the problem up makes it easier to solve, and allows us to reuse parts of our code in other applications. Object-orientation is the most obvious of many attempts to get us closer to this ideal, and yet one of the most successful approaches is almost accidental: the web. Programming languages provide us with functions and classes, and plenty of other ways to modularize our code. This allows us to take our large problem, split it into small parts, and solve those small parts without having to worry about the whole. It also makes it easier to reason about our code. So far, so good, but now that we’ve written our small, independent module, for example to send out e-mails to my customers, we’d like to reuse it in another application. By creating DLLs, JARs or our platform’s package container of choice, we can do just that – provided our new application is on the same platform. Want to use a Java library from C#? Well, good luck – it might be possible, but it’s not going to be smooth sailing. Even if a library exists, it doesn’t mean that using it going to be a pleasant experience. Say I want to use Java to write out an XML document to an output stream. You’d imagine this would be a simple one-liner. You’d be wrong: import org.w3c.dom.*; import java.io.*; import javax.xml.transform.*; import javax.xml.transform.dom.*; import javax.xml.transform.stream.*; private static final void writeDoc(Document doc, OutputStream out) throws IOException { try { Transformer t = TransformerFactory.newInstance().newTransformer(); t.setOutputProperty(OutputKeys.DOCTYPE_SYSTEM, doc.getDoctype().getSystemId()); t.transform(new DOMSource(doc), new StreamResult(out)); } catch (TransformerException e) { throw new AssertionError(e); // Can't happen! } } Most of the time, there is a good chance somebody else has written the code before, but if nobody can understand the interface to that code, nobody’s going to use it. The result is that most of the code we write is just a variation on a theme. Despite our best efforts, we’ve fallen a little short of our ideal, but the web brings us closer. If we want to send e-mails to our customers, we could write an e-mail-sending library. More likely, we’d use an existing one for our language. Even then, we probably wouldn’t have niceties like A/B testing or DKIM signing. Alternatively, we could just fire some HTTP requests at MailChimp, and get a whole slew of features without getting anywhere near the code that implements them. The web is inherently language agnostic. So long as your language can send and receive text over HTTP, and probably parse some JSON, you’re about as well equipped as anybody. Instead of building libraries for a specific language, we can build a service that almost every language can reuse. The text-based nature of HTTP also helps to limit the complexity of the API. As SOAP will attest, you can still make a horrible mess using HTTP, but at least it is an obvious horrible mess. Complex data structures are tedious to marshal to and from text, providing a strong incentive to keep things simple. By contrast, spotting the complexities in a class hierarchy is often not as easy. HTTP doesn’t solve every problem. It probably isn’t such a good idea to use it inside an inner loop that’s executed thousands of times per second. What’s more, the HTTP approach might introduce some new problems. We often need to add a thin shim to each application that we wish to communicate over HTTP. For instance, we might need to write a small plugin in PHP if we want to integrate WordPress into our system. Suddenly, instead of a system written in one language, we’re maintaining a system with several distinct languages and platforms. Even then, we should strive to avoid re-implementing the same old thing. As programmers, we consistently underestimate both the cost of building a system and the ongoing maintenance. If we allow ourselves to integrate existing applications, even if they’re in unfamiliar languages, we save ourselves those development and maintenance costs, as well as being able to pick the best solution for our problem. Thanks to the web, HTTP is often the easiest way to get there.

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  • O'reilly certification in PHP worth it?

    - by editzombie
    I asked this question over on stack overflow but I didn't realise it wasn't really the place for not so technical questions. I've seen quite a few related threads on this forum so I thought I'd try and get some feedback here: This is my first time asking a question on this forum, though I´ve read it a lot. I apologise if this is repeating a thread. I´m interested in getting into web development. I am a video editor by trade but living in Spain the way things are at the moment its very difficult to find work. I have some very basic knowledge of HTML and CSS and a little bit of flash and have designed a few little personal websites myself. I also worked for a online marketing production company where I worked a little on blog design in Blogger amongst other social media. So thats my background, but I´m trying to expand my skills and get into web development as a career or in general part of my skill base, I was thinking particularly about PHP/MySQL. I have worked a little on some of the Lynda.com tutorials and have invested in a book (Sams Teach Yourself PHP, MySQL and Apache). I´m still finding it very difficult to progress. I know I should really try some practice projects (any reccomendations would be welcome). But I was also thinking about doing one of the O´Reilly certification courses and was wondering whether it would be worthwhile for a noob like me. I hear that the courses are associated with an American University which I guess gives it more clout. Any other thoughts you guys have about how to make progress in learning web development would be fantasic. Thanks in advance.

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  • C#: LINQ vs foreach - Round 1.

    - by James Michael Hare
    So I was reading Peter Kellner's blog entry on Resharper 5.0 and its LINQ refactoring and thought that was very cool.  But that raised a point I had always been curious about in my head -- which is a better choice: manual foreach loops or LINQ?    The answer is not really clear-cut.  There are two sides to any code cost arguments: performance and maintainability.  The first of these is obvious and quantifiable.  Given any two pieces of code that perform the same function, you can run them side-by-side and see which piece of code performs better.   Unfortunately, this is not always a good measure.  Well written assembly language outperforms well written C++ code, but you lose a lot in maintainability which creates a big techncial debt load that is hard to offset as the application ages.  In contrast, higher level constructs make the code more brief and easier to understand, hence reducing technical cost.   Now, obviously in this case we're not talking two separate languages, we're comparing doing something manually in the language versus using a higher-order set of IEnumerable extensions that are in the System.Linq library.   Well, before we discuss any further, let's look at some sample code and the numbers.  First, let's take a look at the for loop and the LINQ expression.  This is just a simple find comparison:       // find implemented via LINQ     public static bool FindViaLinq(IEnumerable<int> list, int target)     {         return list.Any(item => item == target);     }         // find implemented via standard iteration     public static bool FindViaIteration(IEnumerable<int> list, int target)     {         foreach (var i in list)         {             if (i == target)             {                 return true;             }         }           return false;     }   Okay, looking at this from a maintainability point of view, the Linq expression is definitely more concise (8 lines down to 1) and is very readable in intention.  You don't have to actually analyze the behavior of the loop to determine what it's doing.   So let's take a look at performance metrics from 100,000 iterations of these methods on a List<int> of varying sizes filled with random data.  For this test, we fill a target array with 100,000 random integers and then run the exact same pseudo-random targets through both searches.                       List<T> On 100,000 Iterations     Method      Size     Total (ms)  Per Iteration (ms)  % Slower     Any         10       26          0.00046             30.00%     Iteration   10       20          0.00023             -     Any         100      116         0.00201             18.37%     Iteration   100      98          0.00118             -     Any         1000     1058        0.01853             16.78%     Iteration   1000     906         0.01155             -     Any         10,000   10,383      0.18189             17.41%     Iteration   10,000   8843        0.11362             -     Any         100,000  104,004     1.8297              18.27%     Iteration   100,000  87,941      1.13163             -   The LINQ expression is running about 17% slower for average size collections and worse for smaller collections.  Presumably, this is due to the overhead of the state machine used to track the iterators for the yield returns in the LINQ expressions, which seems about right in a tight loop such as this.   So what about other LINQ expressions?  After all, Any() is one of the more trivial ones.  I decided to try the TakeWhile() algorithm using a Count() to get the position stopped like the sample Pete was using in his blog that Resharper refactored for him into LINQ:       // Linq form     public static int GetTargetPosition1(IEnumerable<int> list, int target)     {         return list.TakeWhile(item => item != target).Count();     }       // traditionally iterative form     public static int GetTargetPosition2(IEnumerable<int> list, int target)     {         int count = 0;           foreach (var i in list)         {             if(i == target)             {                 break;             }               ++count;         }           return count;     }   Once again, the LINQ expression is much shorter, easier to read, and should be easier to maintain over time, reducing the cost of technical debt.  So I ran these through the same test data:                       List<T> On 100,000 Iterations     Method      Size     Total (ms)  Per Iteration (ms)  % Slower     TakeWhile   10       41          0.00041             128%     Iteration   10       18          0.00018             -     TakeWhile   100      171         0.00171             88%     Iteration   100      91          0.00091             -     TakeWhile   1000     1604        0.01604             94%     Iteration   1000     825         0.00825             -     TakeWhile   10,000   15765       0.15765             92%     Iteration   10,000   8204        0.08204             -     TakeWhile   100,000  156950      1.5695              92%     Iteration   100,000  81635       0.81635             -     Wow!  I expected some overhead due to the state machines iterators produce, but 90% slower?  That seems a little heavy to me.  So then I thought, well, what if TakeWhile() is not the right tool for the job?  The problem is TakeWhile returns each item for processing using yield return, whereas our for-loop really doesn't care about the item beyond using it as a stop condition to evaluate. So what if that back and forth with the iterator state machine is the problem?  Well, we can quickly create an (albeit ugly) lambda that uses the Any() along with a count in a closure (if a LINQ guru knows a better way PLEASE let me know!), after all , this is more consistent with what we're trying to do, we're trying to find the first occurence of an item and halt once we find it, we just happen to be counting on the way.  This mostly matches Any().       // a new method that uses linq but evaluates the count in a closure.     public static int TakeWhileViaLinq2(IEnumerable<int> list, int target)     {         int count = 0;         list.Any(item =>             {                 if(item == target)                 {                     return true;                 }                   ++count;                 return false;             });         return count;     }     Now how does this one compare?                         List<T> On 100,000 Iterations     Method         Size     Total (ms)  Per Iteration (ms)  % Slower     TakeWhile      10       41          0.00041             128%     Any w/Closure  10       23          0.00023             28%     Iteration      10       18          0.00018             -     TakeWhile      100      171         0.00171             88%     Any w/Closure  100      116         0.00116             27%     Iteration      100      91          0.00091             -     TakeWhile      1000     1604        0.01604             94%     Any w/Closure  1000     1101        0.01101             33%     Iteration      1000     825         0.00825             -     TakeWhile      10,000   15765       0.15765             92%     Any w/Closure  10,000   10802       0.10802             32%     Iteration      10,000   8204        0.08204             -     TakeWhile      100,000  156950      1.5695              92%     Any w/Closure  100,000  108378      1.08378             33%     Iteration      100,000  81635       0.81635             -     Much better!  It seems that the overhead of TakeAny() returning each item and updating the state in the state machine is drastically reduced by using Any() since Any() iterates forward until it finds the value we're looking for -- for the task we're attempting to do.   So the lesson there is, make sure when you use a LINQ expression you're choosing the best expression for the job, because if you're doing more work than you really need, you'll have a slower algorithm.  But this is true of any choice of algorithm or collection in general.     Even with the Any() with the count in the closure it is still about 30% slower, but let's consider that angle carefully.  For a list of 100,000 items, it was the difference between 1.01 ms and 0.82 ms roughly in a List<T>.  That's really not that bad at all in the grand scheme of things.  Even running at 90% slower with TakeWhile(), for the vast majority of my projects, an extra millisecond to save potential errors in the long term and improve maintainability is a small price to pay.  And if your typical list is 1000 items or less we're talking only microseconds worth of difference.   It's like they say: 90% of your performance bottlenecks are in 2% of your code, so over-optimizing almost never pays off.  So personally, I'll take the LINQ expression wherever I can because they will be easier to read and maintain (thus reducing technical debt) and I can rely on Microsoft's development to have coded and unit tested those algorithm fully for me instead of relying on a developer to code the loop logic correctly.   If something's 90% slower, yes, it's worth keeping in mind, but it's really not until you start get magnitudes-of-order slower (10x, 100x, 1000x) that alarm bells should really go off.  And if I ever do need that last millisecond of performance?  Well then I'll optimize JUST THAT problem spot.  To me it's worth it for the readability, speed-to-market, and maintainability.

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  • A Good Developer is So Hard to Find

    - by James Michael Hare
    Let me start out by saying I want to damn the writers of the Toughest Developer Puzzle Ever – 2. It is eating every last shred of my free time! But as I've been churning through each puzzle and marvelling at the brain teasers and trivia within, I began to think about interviewing developers and why it seems to be so hard to find good ones.  The problem is, it seems like no matter how hard we try to find the perfect way to separate the chaff from the wheat, inevitably someone will get hired who falls far short of expectations or someone will get passed over for missing a piece of trivia or a tricky brain teaser that could have been an excellent team member.   In shops that are primarily software-producing businesses or other heavily IT-oriented businesses (Microsoft, Amazon, etc) there often exists a much tighter bond between HR and the hiring development staff because development is their life-blood. Unfortunately, many of us work in places where IT is viewed as a cost or just a means to an end. In these shops, too often, HR and development staff may work against each other due to differences in opinion as to what a good developer is or what one is worth.  It seems that if you ask two different people what makes a good developer, often you will get three different opinions.   With the exception of those shops that are purely development-centric (you guys have it much easier!), most other shops have management who have very little knowledge about the development process.  Their view can often be that development is simply a skill that one learns and then once aquired, that developer can produce widgets as good as the next like workers on an assembly-line floor.  On the other side, you have many developers that feel that software development is an art unto itself and that the ability to create the most pure design or know the most obscure of keywords or write the shortest-possible obfuscated piece of code is a good coder.  So is it a skill?  An Art?  Or something entirely in between?   Saying that software is merely a skill and one just needs to learn the syntax and tools would be akin to saying anyone who knows English and can use Word can write a 300 page book that is accurate, meaningful, and stays true to the point.  This just isn't so.  It takes more than mere skill to take words and form a sentence, join those sentences into paragraphs, and those paragraphs into a document.  I've interviewed candidates who could answer obscure syntax and keyword questions and once they were hired could not code effectively at all.  So development must be more than a skill.   But on the other end, we have art.  Is development an art?  Is our end result to produce art?  I can marvel at a piece of code -- see it as concise and beautiful -- and yet that code most perform some stated function with accuracy and efficiency and maintainability.  None of these three things have anything to do with art, per se.  Art is beauty for its own sake and is a wonderful thing.  But if you apply that same though to development it just doesn't hold.  I've had developers tell me that all that matters is the end result and how you code it is entirely part of the art and I couldn't disagree more.  Yes, the end result, the accuracy, is the prime criteria to be met.  But if code is not maintainable and efficient, it would be just as useless as a beautiful car that breaks down once a week or that gets 2 miles to the gallon.  Yes, it may work in that it moves you from point A to point B and is pretty as hell, but if it can't be maintained or is not efficient, it's not a good solution.  So development must be something less than art.   In the end, I think I feel like development is a matter of craftsmanship.  We use our tools and we use our skills and set about to construct something that satisfies a purpose and yet is also elegant and efficient.  There is skill involved, and there is an art, but really it boils down to being able to craft code.  Crafting code is far more than writing code.  Anyone can write code if they know the syntax, but so few people can actually craft code that solves a purpose and craft it well.  So this is what I want to find, I want to find code craftsman!  But how?   I used to ask coding-trivia questions a long time ago and many people still fall back on this.  The thought is that if you ask the candidate some piece of coding trivia and they know the answer it must follow that they can craft good code.  For example:   What C++ keyword can be applied to a class/struct field to allow it to be changed even from a const-instance of that class/struct?  (answer: mutable)   So what do we prove if a candidate can answer this?  Only that they know what mutable means.  One would hope that this would infer that they'd know how to use it, and more importantly when and if it should ever be used!  But it rarely does!  The problem with triva questions is that you will either: Approve a really good developer who knows what some obscure keyword is (good) Reject a really good developer who never needed to use that keyword or is too inexperienced to know how to use it (bad) Approve a really bad developer who googled "C++ Interview Questions" and studied like hell but can't craft (very bad) Many HR departments love these kind of tests because they are short and easy to defend if a legal issue arrises on hiring decisions.  After all it's easy to say a person wasn't hired because they scored 30 out of 100 on some trivia test.  But unfortunately, you've eliminated a large part of your potential developer pool and possibly hired a few duds.  There are times I've hired candidates who knew every trivia question I could throw out them and couldn't craft.  And then there are times I've interviewed candidates who failed all my trivia but who I took a chance on who were my best finds ever.    So if not trivia, then what?  Brain teasers?  The thought is, these type of questions measure the thinking power of a candidate.  The problem is, once again, you will either: Approve a good candidate who has never heard the problem and can solve it (good) Reject a good candidate who just happens not to see the "catch" because they're nervous or it may be really obscure (bad) Approve a candidate who has studied enough interview brain teasers (once again, you can google em) to recognize the "catch" or knows the answer already (bad). Once again, you're eliminating good candidates and possibly accepting bad candidates.  In these cases, I think testing someone with brain teasers only tests their ability to answer brain teasers, not the ability to craft code. So how do we measure someone's ability to craft code?  Here's a novel idea: have them code!  Give them a computer and a compiler, or a whiteboard and a pen, or paper and pencil and have them construct a piece of code.  It just makes sense that if we're going to hire someone to code we should actually watch them code.  When they're done, we can judge them on several criteria: Correctness - does the candidate's solution accurately solve the problem proposed? Accuracy - is the candidate's solution reasonably syntactically correct? Efficiency - did the candidate write or use the more efficient data structures or algorithms for the job? Maintainability - was the candidate's code free of obfuscation and clever tricks that diminish readability? Persona - are they eager and willing or aloof and egotistical?  Will they work well within your team? It may sound simple, or it may sound crazy, but when I'm looking to hire a developer, I want to see them actually develop well-crafted code.

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  • More Fun with C# Iterators and Generators

    - by James Michael Hare
    In my last post, I talked quite a bit about iterators and how they can be really powerful tools for filtering a list of items down to a subset of items.  This had both pros and cons over returning a full collection, which, in summary, were:   Pros: If traversal is only partial, does not have to visit rest of collection. If evaluation method is costly, only incurs that cost on elements visited. Adds little to no garbage collection pressure.    Cons: Very slight performance impact if you know caller will always consume all items in collection. And as we saw in the last post, that con for the cost was very, very small and only really became evident on very tight loops consuming very large lists completely.    One of the key items to note, though, is the garbage!  In the traditional (return a new collection) method, if you have a 1,000,000 element collection, and wish to transform or filter it in some way, you have to allocate space for that copy of the collection.  That is, say you have a collection of 1,000,000 items and you want to double every item in the collection.  Well, that means you have to allocate a collection to hold those 1,000,000 items to return, which is a lot especially if you are just going to use it once and toss it.   Iterators, though, don't have this problem.  Each time you visit the node, it would return the doubled value of the node (in this example) and not allocate a second collection of 1,000,000 doubled items.  Do you see the distinction?  In both cases, we're consuming 1,000,000 items.  But in one case we pass back each doubled item which is just an int (for example's sake) on the stack and in the other case, we allocate a list containing 1,000,000 items which then must be garbage collected.   So iterators in C# are pretty cool, eh?  Well, here's one more thing a C# iterator can do that a traditional "return a new collection" transformation can't!   It can return **unbounded** collections!   I know, I know, that smells a lot like an infinite loop, eh?  Yes and no.  Basically, you're relying on the caller to put the bounds on the list, and as long as the caller doesn't you keep going.  Consider this example:   public static class Fibonacci {     // returns the infinite fibonacci sequence     public static IEnumerable<int> Sequence()     {         int iteration = 0;         int first = 1;         int second = 1;         int current = 0;         while (true)         {             if (iteration++ < 2)             {                 current = 1;             }             else             {                 current = first + second;                 second = first;                 first = current;             }             yield return current;         }     } }   Whoa, you say!  Yes, that's an infinite loop!  What the heck is going on there?  Yes, that was intentional.  Would it be better to have a fibonacci sequence that returns only a specific number of items?  Perhaps, but that wouldn't give you the power to defer the execution to the caller.   The beauty of this function is it is as infinite as the sequence itself!  The fibonacci sequence is unbounded, and so is this method.  It will continue to return fibonacci numbers for as long as you ask for them.  Now that's not something you can do with a traditional method that would return a collection of ints representing each number.  In that case you would eventually run out of memory as you got to higher and higher numbers.  This method, though, never runs out of memory.   Now, that said, you do have to know when you use it that it is an infinite collection and bound it appropriately.  Fortunately, Linq provides a lot of these extension methods for you!   Let's say you only want the first 10 fibonacci numbers:       foreach(var fib in Fibonacci.Sequence().Take(10))     {         Console.WriteLine(fib);     }   Or let's say you only want the fibonacci numbers that are less than 100:       foreach(var fib in Fibonacci.Sequence().TakeWhile(f => f < 100))     {         Console.WriteLine(fib);     }   So, you see, one of the nice things about iterators is their power to work with virtually any size (even infinite) collections without adding the garbage collection overhead of making new collections.    You can also do fun things like this to make a more "fluent" interface for for loops:   // A set of integer generator extension methods public static class IntExtensions {     // Begins counting to inifity, use To() to range this.     public static IEnumerable<int> Every(this int start)     {         // deliberately avoiding condition because keeps going         // to infinity for as long as values are pulled.         for (var i = start; ; ++i)         {             yield return i;         }     }     // Begins counting to infinity by the given step value, use To() to     public static IEnumerable<int> Every(this int start, int byEvery)     {         // deliberately avoiding condition because keeps going         // to infinity for as long as values are pulled.         for (var i = start; ; i += byEvery)         {             yield return i;         }     }     // Begins counting to inifity, use To() to range this.     public static IEnumerable<int> To(this int start, int end)     {         for (var i = start; i <= end; ++i)         {             yield return i;         }     }     // Ranges the count by specifying the upper range of the count.     public static IEnumerable<int> To(this IEnumerable<int> collection, int end)     {         return collection.TakeWhile(item => item <= end);     } }   Note that there are two versions of each method.  One that starts with an int and one that starts with an IEnumerable<int>.  This is to allow more power in chaining from either an existing collection or from an int.  This lets you do things like:   // count from 1 to 30 foreach(var i in 1.To(30)) {     Console.WriteLine(i); }     // count from 1 to 10 by 2s foreach(var i in 0.Every(2).To(10)) {     Console.WriteLine(i); }     // or, if you want an infinite sequence counting by 5s until something inside breaks you out... foreach(var i in 0.Every(5)) {     if (someCondition)     {         break;     }     ... }     Yes, those are kinda play functions and not particularly useful, but they show some of the power of generators and extension methods to form a fluid interface.   So what do you think?  What are some of your favorite generators and iterators?

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  • Combining Shared Secret and Username Token – Azure Service Bus

    - by Michael Stephenson
    As discussed in the introduction article this walkthrough will explain how you can implement WCF security with the Windows Azure Service Bus to ensure that you can protect your endpoint in the cloud with a shared secret but also flow through a username token so that in your listening WCF service you will be able to identify who sent the message. This could either be in the form of an application or a user depending on how you want to use your token. Prerequisites Before going into the walk through I want to explain a few assumptions about the scenario we are implementing but to keep the article shorter I am not going to walk through all of the steps in how to setup some of this. In the solution we have a simple console application which will represent the client application. There is also the services WCF application which contains the WCF service we will expose via the Windows Azure Service Bus. The WCF Service application in this example was hosted in IIS 7 on Windows 2008 R2 with AppFabric Server installed and configured to auto-start the WCF listening services. I am not going to go through significant detail around the IIS setup because it should not matter in relation to this article however if you want to understand more about how to configure WCF and IIS for such a scenario please refer to the following paper which goes into a lot of detail about how to configure this. The link is: http://tinyurl.com/8s5nwrz   The Service Component To begin with let's look at the service component and how it can be configured to listen to the service bus using a shared secret but to also accept a username token from the client. In the sample the service component is called Acme.Azure.ServiceBus.Poc.UN.Services. It has a single service which is the Visual Studio template for a WCF service when you add a new WCF Service Application so we have a service called Service1 with its Echo method. Nothing special so far!.... The next step is to look at the web.config file to see how we have configured the WCF service. In the services section of the WCF configuration you can see I have created my service and I have created a local endpoint which I simply used to do a little bit of diagnostics and to check it was working, but more importantly there is the Windows Azure endpoint which is using the ws2007HttpRelayBinding (note that this should also work just the same if your using netTcpRelayBinding). The key points to note on the above picture are the service behavior called MyServiceBehaviour and the service bus endpoints behavior called MyEndpointBehaviour. We will go into these in more detail later.   The Relay Binding The relay binding for the service has been configured to use the TransportWithMessageCredential security mode. This is the important bit where the transport security really relates to the interaction between the service and listening to the Azure Service Bus and the message credential is where we will use our username token like we have specified in the message/clientCrentialType attribute. Note also that we have left the relayClientAuthenticationType set to RelayAccessToken. This means that authentication will be made against ACS for accessing the service bus and messages will not be accepted from any sender who has not been authenticated by ACS.   The Endpoint Behaviour In the below picture you can see the endpoint behavior which is configured to use the shared secret client credential for accessing the service bus and also for diagnostic purposes I have included the service registry element. Hopefully if you are familiar with using Windows Azure Service Bus relay feature the above is very familiar to you and this is a very common setup for this section. There is nothing specific to the username token implementation here. The Service Behaviour Now we come to the bit with most of the username token bits in it. When you configure the service behavior I have included the serviceCredentials element and then setup to use userNameAuthentication and you can see that I have created my own custom username token validator.   This setup means that WCF will hand off to my class for validating the username token details. I have also added the serviceSecurityAudit element to give me a simple auditing of access capability. My UsernamePassword Validator The below picture shows you the details of the username password validator class I have implemented. WCF will hand off to this class when validating the token and give me a nice way to check the token credentials against an on-premise store. You have all of the validation features with a non-service bus WCF implementation available such as validating the username password against active directory or ASP.net membership features or as in my case above something much simpler.   The Client Now let's take a look at the client side of this solution and how we can configure the client to authenticate against ACS but also send a username token over to the service component so it can implement additional security checks on-premise. I have a console application and in the program class I want to use the proxy generated with Add Service Reference to send a message via the Azure Service Bus. You can see in my WCF client configuration below I have setup my details for the azure service bus url and am using the ws2007HttpRelayBinding. Next is my configuration for the relay binding. You can see below I have configured security to use TransportWithMessageCredential so we will flow the username token with the message and also the RelayAccessToken relayClientAuthenticationType which means the component will validate against ACS before being allowed to access the relay endpoint to send a message.     After the binding we need to configure the endpoint behavior like in the below picture. This is the normal configuration to use a shared secret for accessing a Service Bus endpoint.   Finally below we have the code of the client in the console application which will call the service bus. You can see that we have created our proxy and then made a normal call to a WCF service but this time we have also set the ClientCredentials to use the appropriate username and password which will be flown through the service bus and to our service which will validate them.     Conclusion As you can see from the above walkthrough it is not too difficult to configure a service to use both a shared secret and username token at the same time. This gives you the power and protection offered by the access control service in the cloud but also the ability to flow additional tokens to the on-premise component for additional security features to be implemented. Sample The sample used in this post is available at the following location: https://s3.amazonaws.com/CSCBlogSamples/Acme.Azure.ServiceBus.Poc.UN.zip

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  • Combining Shared Secret and Certificates

    - by Michael Stephenson
    As discussed in the introduction article this walkthrough will explain how you can implement WCF security with the Windows Azure Service Bus to ensure that you can protect your endpoint in the cloud with a shared secret but also combine this with certificates so that you can identify the sender of the message.   Prerequisites As in the previous article before going into the walk through I want to explain a few assumptions about the scenario we are implementing but to keep the article shorter I am not going to walk through all of the steps in how to setup some of this. In the solution we have a simple console application which will represent the client application. There is also the services WCF application which contains the WCF service we will expose via the Windows Azure Service Bus. The WCF Service application in this example was hosted in IIS 7 on Windows 2008 R2 with AppFabric Server installed and configured to auto-start the WCF listening services. I am not going to go through significant detail around the IIS setup because it should not matter in relation to this article however if you want to understand more about how to configure WCF and IIS for such a scenario please refer to the following paper which goes into a lot of detail about how to configure this. The link is: http://tinyurl.com/8s5nwrz   Setting up the Certificates To keep the post and sample simple I am going to use the local computer store for all certificates but this bit is really just the same as setting up certificates for an example where you are using WCF without using Windows Azure Service Bus. In the sample I have included two batch files which you can use to create the sample certificates or remove them. Basically you will end up with: A certificate called PocServerCert in the personal store for the local computer which will be used by the WCF Service component A certificate called PocClientCert in the personal store for the local computer which will be used by the client application A root certificate in the Root store called PocRootCA with its associated revocation list which is the root from which the client and server certificates were created   For the sample Im just using development certificates like you would normally, and you can see exactly how these are configured and placed in the stores from the batch files in the solution using makecert and certmgr.   The Service Component To begin with let's look at the service component and how it can be configured to listen to the service bus using a shared secret but to also accept a username token from the client. In the sample the service component is called Acme.Azure.ServiceBus.Poc.Cert.Services. It has a single service which is the Visual Studio template for a WCF service when you add a new WCF Service Application so we have a service called Service1 with its Echo method. Nothing special so far!.... The next step is to look at the web.config file to see how we have configured the WCF service. In the services section of the WCF configuration you can see I have created my service and I have created a local endpoint which I simply used to do a little bit of diagnostics and to check it was working, but more importantly there is the Windows Azure endpoint which is using the ws2007HttpRelayBinding (note that this should also work just the same if your using netTcpRelayBinding). The key points to note on the above picture are the service behavior called MyServiceBehaviour and the service bus endpoints behavior called MyEndpointBehaviour. We will go into these in more detail later.   The Relay Binding The relay binding for the service has been configured to use the TransportWithMessageCredential security mode. This is the important bit where the transport security really relates to the interaction between the service and listening to the Azure Service Bus and the message credential is where we will use our certificate like we have specified in the message/clientCrentialType attribute. Note also that we have left the relayClientAuthenticationType set to RelayAccessToken. This means that authentication will be made against ACS for accessing the service bus and messages will not be accepted from any sender who has not been authenticated by ACS.   The Endpoint Behaviour In the below picture you can see the endpoint behavior which is configured to use the shared secret client credential for accessing the service bus and also for diagnostic purposes I have included the service registry element.     Hopefully if you are familiar with using Windows Azure Service Bus relay feature the above is very familiar to you and this is a very common setup for this section. There is nothing specific to the username token implementation here. The Service Behaviour Now we come to the bit with most of the certificate stuff in it. When you configure the service behavior I have included the serviceCredentials element and then setup to use the clientCertificate check and also specifying the serviceCertificate with information on how to find the servers certificate in the store.     I have also added a serviceAuthorization section where I will implement my own authorization component to perform additional security checks after the service has validated that the message was signed with a good certificate. I also have the same serviceSecurityAudit configuration to log access to my service. My Authorization Manager The below picture shows you implementation of my authorization manager. WCF will eventually hand off the message to my authorization component before it calls the service code. This is where I can perform some logic to check if the identity is allowed to access resources. In this case I am simple rejecting messages from anyone except the PocClientCertificate.     The Client Now let's take a look at the client side of this solution and how we can configure the client to authenticate against ACS but also send a certificate over to the service component so it can implement additional security checks on-premise. I have a console application and in the program class I want to use the proxy generated with Add Service Reference to send a message via the Azure Service Bus. You can see in my WCF client configuration below I have setup my details for the azure service bus url and am using the ws2007HttpRelayBinding.   Next is my configuration for the relay binding. You can see below I have configured security to use TransportWithMessageCredential so we will flow the token from a certificate with the message and also the RelayAccessToken relayClientAuthenticationType which means the component will validate against ACS before being allowed to access the relay endpoint to send a message.     After the binding we need to configure the endpoint behavior like in the below picture. This contains the normal transportClientEndpointBehaviour to setup the ACS shared secret configuration but we have also configured the clientCertificate to look for the PocClientCert.     Finally below we have the code of the client in the console application which will call the service bus. You can see that we have created our proxy and then made a normal call to a WCF in exactly the normal way but the configuration will jump in and ensure that a token is passed representing the client certificate.     Conclusion As you can see from the above walkthrough it is not too difficult to configure a service to use both a shared secret and certificate based token at the same time. This gives you the power and protection offered by the access control service in the cloud but also the ability to flow additional tokens to the on-premise component for additional security features to be implemented. Sample The sample used in this post is available at the following location: https://s3.amazonaws.com/CSCBlogSamples/Acme.Azure.ServiceBus.Poc.Cert.zip

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  • Code Reuse is (Damn) Hard

    - by James Michael Hare
    Being a development team lead, the task of interviewing new candidates was part of my job.  Like any typical interview, we started with some easy questions to get them warmed up and help calm their nerves before hitting the hard stuff. One of those easier questions was almost always: “Name some benefits of object-oriented development.”  Nearly every time, the candidate would chime in with a plethora of canned answers which typically included: “it helps ease code reuse.”  Of course, this is a gross oversimplification.  Tools only ease reuse, its developers that ultimately can cause code to be reusable or not, regardless of the language or methodology. But it did get me thinking…  we always used to say that as part of our mantra as to why Object-Oriented Programming was so great.  With polymorphism, inheritance, encapsulation, etc. we in essence set up the concepts to help facilitate reuse as much as possible.  And yes, as a developer now of many years, I unquestionably held that belief for ages before it really struck me how my views on reuse have jaded over the years.  In fact, in many ways Agile rightly eschews reuse as taking a backseat to developing what's needed for the here and now.  It used to be I was in complete opposition to that view, but more and more I've come to see the logic in it.  Too many times I've seen developers (myself included) get lost in design paralysis trying to come up with the perfect abstraction that would stand all time.  Nearly without fail, all of these pieces of code become obsolete in a matter of months or years. It’s not that I don’t like reuse – it’s just that reuse is hard.  In fact, reuse is DAMN hard.  Many times it is just a distraction that eats up architect and developer time, and worse yet can be counter-productive and force wrong decisions.  Now don’t get me wrong, I love the idea of reusable code when it makes sense.  These are in the few cases where you are designing something that is inherently reusable.  The problem is, most business-class code is inherently unfit for reuse! Furthermore, the code that is reusable will often fail to be reused if you don’t have the proper framework in place for effective reuse that includes standardized versioning, building, releasing, and documenting the components.  That should always be standard across the board when promoting reusable code.  All of this is hard, and it should only be done when you have code that is truly reusable or you will be exerting a large amount of development effort for very little bang for your buck. But my goal here is not to get into how to reuse (that is a topic unto itself) but what should be reused.  First, let’s look at an extension method.  There’s many times where I want to kick off a thread to handle a task, then when I want to reign that thread in of course I want to do a Join on it.  But what if I only want to wait a limited amount of time and then Abort?  Well, I could of course write that logic out by hand each time, but it seemed like a great extension method: 1: public static class ThreadExtensions 2: { 3: public static bool JoinOrAbort(this Thread thread, TimeSpan timeToWait) 4: { 5: bool isJoined = false; 6:  7: if (thread != null) 8: { 9: isJoined = thread.Join(timeToWait); 10:  11: if (!isJoined) 12: { 13: thread.Abort(); 14: } 15: } 16: return isJoined; 17: } 18: } 19:  When I look at this code, I can immediately see things that jump out at me as reasons why this code is very reusable.  Some of them are standard OO principles, and some are kind-of home grown litmus tests: Single Responsibility Principle (SRP) – The only reason this extension method need change is if the Thread class itself changes (one responsibility). Stable Dependencies Principle (SDP) – This method only depends on classes that are more stable than it is (System.Threading.Thread), and in itself is very stable, hence other classes may safely depend on it. It is also not dependent on any business domain, and thus isn't subject to changes as the business itself changes. Open-Closed Principle (OCP) – This class is inherently closed to change. Small and Stable Problem Domain – This method only cares about System.Threading.Thread. All-or-None Usage – A user of a reusable class should want the functionality of that class, not parts of that functionality.  That’s not to say they most use every method, but they shouldn’t be using a method just to get half of its result. Cost of Reuse vs. Cost to Recreate – since this class is highly stable and minimally complex, we can offer it up for reuse very cheaply by promoting it as “ready-to-go” and already unit tested (important!) and available through a standard release cycle (very important!). Okay, all seems good there, now lets look at an entity and DAO.  I don’t know about you all, but there have been times I’ve been in organizations that get the grand idea that all DAOs and entities should be standardized and shared.  While this may work for small or static organizations, it’s near ludicrous for anything large or volatile. 1: namespace Shared.Entities 2: { 3: public class Account 4: { 5: public int Id { get; set; } 6:  7: public string Name { get; set; } 8:  9: public Address HomeAddress { get; set; } 10:  11: public int Age { get; set;} 12:  13: public DateTime LastUsed { get; set; } 14:  15: // etc, etc, etc... 16: } 17: } 18:  19: ... 20:  21: namespace Shared.DataAccess 22: { 23: public class AccountDao 24: { 25: public Account FindAccount(int id) 26: { 27: // dao logic to query and return account 28: } 29:  30: ... 31:  32: } 33: } Now to be fair, I’m not saying there doesn’t exist an organization where some entites may be extremely static and unchanging.  But at best such entities and DAOs will be problematic cases of reuse.  Let’s examine those same tests: Single Responsibility Principle (SRP) – The reasons to change for these classes will be strongly dependent on what the definition of the account is which can change over time and may have multiple influences depending on the number of systems an account can cover. Stable Dependencies Principle (SDP) – This method depends on the data model beneath itself which also is largely dependent on the business definition of an account which can be very inherently unstable. Open-Closed Principle (OCP) – This class is not really closed for modification.  Every time the account definition may change, you’d need to modify this class. Small and Stable Problem Domain – The definition of an account is inherently unstable and in fact may be very large.  What if you are designing a system that aggregates account information from several sources? All-or-None Usage – What if your view of the account encompasses data from 3 different sources but you only care about one of those sources or one piece of data?  Should you have to take the hit of looking up all the other data?  On the other hand, should you have ten different methods returning portions of data in chunks people tend to ask for?  Neither is really a great solution. Cost of Reuse vs. Cost to Recreate – DAOs are really trivial to rewrite, and unless your definition of an account is EXTREMELY stable, the cost to promote, support, and release a reusable account entity and DAO are usually far higher than the cost to recreate as needed. It’s no accident that my case for reuse was a utility class and my case for non-reuse was an entity/DAO.  In general, the smaller and more stable an abstraction is, the higher its level of reuse.  When I became the lead of the Shared Components Committee at my workplace, one of the original goals we looked at satisfying was to find (or create), version, release, and promote a shared library of common utility classes, frameworks, and data access objects.  Now, of course, many of you will point to nHibernate and Entity for the latter, but we were looking at larger, macro collections of data that span multiple data sources of varying types (databases, web services, etc). As we got deeper and deeper in the details of how to manage and release these items, it quickly became apparent that while the case for reuse was typically a slam dunk for utilities and frameworks, the data access objects just didn’t “smell” right.  We ended up having session after session of design meetings to try and find the right way to share these data access components. When someone asked me why it was taking so long to iron out the shared entities, my response was quite simple, “Reuse is hard...”  And that’s when I realized, that while reuse is an awesome goal and we should strive to make code maintainable, often times you end up creating far more work for yourself than necessary by trying to force code to be reusable that inherently isn’t. Think about classes the times you’ve worked in a company where in the design session people fight over the best way to implement a class to make it maximally reusable, extensible, and any other buzzwordable.  Then think about how quickly that design became obsolete.  Many times I set out to do a project and think, “yes, this is the best design, I can extend it easily!” only to find out the business requirements change COMPLETELY in such a way that the design is rendered invalid.  Code, in general, tends to rust and age over time.  As such, writing reusable code can often be difficult and many times ends up being a futile exercise and worse yet, sometimes makes the code harder to maintain because it obfuscates the design in the name of extensibility or reusability. So what do I think are reusable components? Generic Utility classes – these tend to be small classes that assist in a task and have no business context whatsoever. Implementation Abstraction Frameworks – home-grown frameworks that try to isolate changes to third party products you may be depending on (like writing a messaging abstraction layer for publishing/subscribing that is independent of whether you use JMS, MSMQ, etc). Simplification and Uniformity Frameworks – To some extent this is similar to an abstraction framework, but there may be one chosen provider but a development shop mandate to perform certain complex items in a certain way.  Or, perhaps to simplify and dumb-down a complex task for the average developer (such as implementing a particular development-shop’s method of encryption). And what are less reusable? Application and Business Layers – tend to fluctuate a lot as requirements change and new features are added, so tend to be an unstable dependency.  May be reused across applications but also very volatile. Entities and Data Access Layers – these tend to be tuned to the scope of the application, so reusing them can be hard unless the abstract is very stable. So what’s the big lesson?  Reuse is hard.  In fact it’s damn hard.  And much of the time I’m not convinced we should focus too hard on it. If you’re designing a utility or framework, then by all means design it for reuse.  But you most also really set down a good versioning, release, and documentation process to maximize your chances.  For anything else, design it to be maintainable and extendable, but don’t waste the effort on reusability for something that most likely will be obsolete in a year or two anyway.

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  • Timeout Considerations for Solicit Response

    - by Michael Stephenson
    Background One of the clients I work with had been experiencing some issues for a while surrounding web service timeouts.  It's been a little challenging to work through the problems due to limitations in the diagnostic information available from one of the applications, but I learned some interesting things while troubleshooting the problem which don't seem to have been discussed much in the community so I thought I'd share my findings. In the scenario we have BizTalk trying to make calls to a .net web service which was exposed as a WSE 2 endpoint.  In the process BizTalk will try to make a large number of concurrent web service calls to the application, and the backend application has more than enough infrastructure and capability to handle the load. We have configured the <ConnectionManagement> section of the BizTalk configuration file to support up to 100 concurrent connections from each of our 2 BizTalk send servers to the web servers of the application. The problem we were facing was that the BizTalk side was reporting a significant number of timeouts when calling the web service.   One of the biggest issues was the challenge of being able to correlate a message from BizTalk to the IIS log in the .net application and the custom logs in the application especially when there was a fairly large number of servers hosting the web services.  However the key moment came when we were able to identify a specific call which had taken 40 seconds to execute on the server (yes a long time I know but that's a different story!).  Anyway we were able to identify that this had timed out on the BizTalk side.  Based on the normal 2 minute timeout we knew something unexpected was going on. From here I decided to do some experimentation and I wanted to start outside of BizTalk because my hunch was this was not a BizTalk behaviour but something which was being highlighted by BizTalk because of our large load.     Server-side - Sample Web Service To begin with I created a sample web service.  Nothing special just a vanilla asmx web service hosted in IIS6 on Windows 2003 Standard Edition.  The web service is just a hello world style web service as shown in the below picture.  The only key feature is that the server side web method has a 30 second sleep in it and will trace out some information before and after the thread is set to sleep.      In the configuration for this web service there again is nothing special it's pretty much the most plain simple web service you could build. Client-Side To begin looking at what was happening with our example I created a number of different ways to consume the web service. SoapHttpClientProtocol Example I created a small application which would use a normal proxy generated to call the web service.  It would iterate around a loop and make calls using the begin/end methods so I can do this asynchronously.  I would do a loop of 20 calls with the ConnectionManager configuration section supporting only 5 concurrent connections to the server.     <connectionManagement> <remove address="*"/> <add address = "*" maxconnection = "12" /> <add address = "http://<ServerName>" maxconnection = "5" />                         </connectionManagement> </system.net>     The below picture shows an example of the service calling code, key points are: I have configured the timeout of 40 seconds for the proxy I am using the asynchronous methods on the proxy to call the web service         The Test I would run the client and execute 21 calls to the web service.   The Results  Below is the client side trace showing what's happening on the client. In the below diagram is the web service side trace showing what's happening on the server Some observations on the results are: All of the calls were successful from the clients perspective You could see the next call starting on the server as soon as the previous one had completed Calls took significantly longer than 40 seconds from the start of our call to the return. In fact call 20 took 2 minutes and 30 seconds from the perspective of my code to execute even though I had set the timeout to 40 seconds     WSE 2 Sample In the second example I used the exact same code to call the web service again with a single exception that I modified the web service proxy to derive from WebServiceClient protocol which is part of WSE 2 (using SP3).  The below picture shows the basic code and the key points are: I have configured the timeout of 40 seconds for the proxy I am using the asynchronous methods on the proxy to call the web service        The Test This test would execute 21 calls from the client to the web service.   The Results  The below trace is from the client side: The below trace is from the server side:   Some observations on the trace results for this scenario are: With call 4 if you look at the server side trace it did not start executing on the server for a number of seconds after the other 4 initial calls which were accepted by the server. I re-ran the test and this happened a couple of times and not on most others so at this point I'm just putting this down to something unexpected happening on the development machine and we will leave this observation out of scope of this article. You can see that the client side trace statement executed almost immediately in all cases All calls after the initial few calls would timeout On the client side the calls that did timeout; timed out in a longer duration than the 40 seconds we set as the timeout You can see that as calls were completing on the server the next calls were starting to come through The calls that timed out on the client did actually connect to the server and their server side execution completed successfully     Elaboration on the findings Based on the above observations I have drawn the below sequence diagram to illustrate conceptually what is happening.  Everything except the final web service object is on the client side of the call. In the diagram below I've put two notes on the Web Service Proxy to show the two different places where the different base classes seem to start their timeout counters. From the earlier samples we can work out that the timeout counter for the WSE web service proxy starts before the one for the SoapHttpClientProtocol proxy and the WSE one includes the time to get a connection from the pool; whereas the Soap proxy timeout just covers the method execution. One interesting observation is if we rerun the above sample and increase the number of calls from 21 to 100,000 then for the WSE sample we will see a similar pattern where everything after the first few calls will timeout on the client as soon as it makes a connection to the server whereas the soap proxy will happily plug away and process all of the calls without a single timeout. I have actually set the sample running overnight and this did happen. At this point you are probably thinking the same thoughts I was at the time about the differences in behaviour and which is right and why are they different? I'm not sure there is a definitive answer to this in the documentation, or at least not that I could find! I think you just have to consider that they are different and they could have different effects depending on your messaging solution. In lots of situations this is just not an issue as your concurrent requests doesn't get to the situation where you end up throttling the web service calls on the client side, however this is definitely more common with an integration broker such as BizTalk where you often have high throughput requirements.  Some of the considerations you should make Based on this behaviour you should be aware of the following: In a .net application if you are making lots of concurrent web service calls from an application in an asynchronous manner your user may thing they are experiencing poor performance but you think your web service is working well. The problem could be that the client will have a default of 2 connections to remote servers so you should bear this in mind When you are developing a BizTalk solution or a .net solution with the WSE 2 stack you may experience timeouts under load and throttling the number of connections using the max connections element in the configuration file will not help you For an application using WSE2 or SoapHttpClientProtocol an expired timeout will not throw an error until after a connection to the server has been made so you should consider this in your transaction and durability patterns     Our Work Around In the short term for our specific scenario we know that we can handle this by just increasing our timeout value.  There is only a specific small window when we get lots of concurrent traffic that causes this scenario so we should be able to increase the timeout to take into consideration the additional client side wait, and on the odd occasion where we do get a timeout the BizTalk send port retry will handle this. What was causing our original problem was that for that short window we were getting a lot of retries which significantly increased the load on our send servers and highlighted the issue.  Longer Term Solution As a longer term solution this really gives us more ammunition to argue a migration to WCF. The application we are calling has some factors which limit the protocols we can use but with WCF we would have more control on the various timeout options because in WCF you can configure specific parts of the timeout. Summary I've had this blog post on my to do list for ages but hopefully it will be useful to some people to just understand this behaviour and to possibly help you with some performance issues you may have. I do not believe there is too much in the way of documentation particularly around WSE2 and ASMX in this area so again another bit of ammunition for migrating to WCF. I'll try to do a follow up post with the sample for WCF to show how this changes things.

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  • LINQ to Entities for subtracting 2 dates

    - by Michael I
    I am trying to determine the number of days between 2 dates using LINQ with Entity Framework. It is telling me that it does not recognize Subtract on the System.TimeSpan class Here is my where portion of the LINQ query. where ((DateTime.Now.Subtract(vid.CreatedDate).TotalDays < maxAgeInDays)) Here is the error I receive in the VS.NET debugger {"LINQ to Entities does not recognize the method 'System.TimeSpan Subtract(System.DateTime)' method, and this method cannot be translated into a store expression."} Am I doing something wrong or is there a better way to get the number of days between 2 DateTimes in the entity framework? thanks Michael

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  • "Gtk-WARNING **: cannot open display: " when using execve to launch a Gtk program on ubuntu

    - by michael
    Hi, I have the following c program which launches a Gtk Program on ubuntu: #include <unistd.h> int main( int argc, const char* argv[] ) { char *args[2] = { "testarg", 0 }; char *envp[1] = { 0 }; execve("/home/michael/MyGtkApp",args,envp); } I get "Gtk-WARNING **: cannot open display: " and my program is not launched. I have tried setting char *envp[1] = {"DISPLAY:0.0"}; and execute 'xhost +' , I dont' see the 'cannot open display' warning, but my program is still not launched. Does anyone know how to fix my problem? Thank you.

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