Search Results

Search found 4999 results on 200 pages for 'derived instances'.

Page 51/200 | < Previous Page | 47 48 49 50 51 52 53 54 55 56 57 58  | Next Page >

• Meet the New Windows Azure

  - by ScottGu

  Today we are releasing a major set of improvements to Windows Azure.  Below is a short-summary of just a few of them: New Admin Portal and Command Line Tools Today’s release comes with a new Windows Azure portal that will enable you to manage all features and services offered on Windows Azure in a seamless, integrated way.  It is very fast and fluid, supports filtering and sorting (making it much easier to use for large deployments), works on all browsers, and offers a lot of great new features – including built-in VM, Web site, Storage, and Cloud Service monitoring support. The new portal is built on top of a REST-based management API within Windows Azure – and everything you can do through the portal can also be programmed directly against this Web API. We are also today releasing command-line tools (which like the portal call the REST Management APIs) to make it even easier to script and automate your administration tasks.  We are offering both a Powershell (for Windows) and Bash (for Mac and Linux) set of tools to download.  Like our SDKs, the code for these tools is hosted on GitHub under an Apache 2 license. Virtual Machines Windows Azure now supports the ability to deploy and run durable VMs in the cloud.  You can easily create these VMs using a new Image Gallery built-into the new Windows Azure Portal, or alternatively upload and run your own custom-built VHD images. Virtual Machines are durable (meaning anything you install within them persists across reboots) and you can use any OS with them.  Our built-in image gallery includes both Windows Server images (including the new Windows Server 2012 RC) as well as Linux images (including Ubuntu, CentOS, and SUSE distributions).  Once you create a VM instance you can easily Terminal Server or SSH into it in order to configure and customize the VM however you want (and optionally capture your own image snapshot of it to use when creating new VM instances).  This provides you with the flexibility to run pretty much any workload within Windows Azure.   The new Windows Azure Portal provides a rich set of management features for Virtual Machines – including the ability to monitor and track resource utilization within them.  Our new Virtual Machine support also enables the ability to easily attach multiple data-disks to VMs (which you can then mount and format as drives).  You can optionally enable geo-replication support on these – which will cause Windows Azure to continuously replicate your storage to a secondary data-center at least 400 miles away from your primary data-center as a backup. We use the same VHD format that is supported with Windows virtualization today (and which we’ve released as an open spec), which enables you to easily migrate existing workloads you might already have virtualized into Windows Azure.  We also make it easy to download VHDs from Windows Azure, which also provides the flexibility to easily migrate cloud-based VM workloads to an on-premise environment.  All you need to do is download the VHD file and boot it up locally, no import/export steps required. Web Sites Windows Azure now supports the ability to quickly and easily deploy ASP.NET, Node.js and PHP web-sites to a highly scalable cloud environment that allows you to start small (and for free) and then scale up as your traffic grows.  You can create a new web site in Azure and have it ready to deploy to in under 10 seconds: The new Windows Azure Portal provides built-in administration support for Web sites – including the ability to monitor and track resource utilization in real-time: You can deploy to web-sites in seconds using FTP, Git, TFS and Web Deploy.  We are also releasing tooling updates today for both Visual Studio and Web Matrix that enable developers to seamlessly deploy ASP.NET applications to this new offering.  The VS and Web Matrix publishing support includes the ability to deploy SQL databases as part of web site deployment – as well as the ability to incrementally update database schema with a later deployment. You can integrate web application publishing with source control by selecting the “Set up TFS publishing” or “Set up Git publishing” links on a web-site’s dashboard: Doing do will enable integration with our new TFS online service (which enables a full TFS workflow – including elastic build and testing support), or create a Git repository that you can reference as a remote and push deployments to.  Once you push a deployment using TFS or Git, the deployments tab will keep track of the deployments you make, and enable you to select an older (or newer) deployment and quickly redeploy your site to that snapshot of the code.  This provides a very powerful DevOps workflow experience.   Windows Azure now allows you to deploy up to 10 web-sites into a free, shared/multi-tenant hosting environment (where a site you deploy will be one of multiple sites running on a shared set of server resources).  This provides an easy way to get started on projects at no cost. You can then optionally upgrade your sites to run in a “reserved mode” that isolates them so that you are the only customer within a virtual machine: And you can elastically scale the amount of resources your sites use – allowing you to increase your reserved instance capacity as your traffic scales: Windows Azure automatically handles load balancing traffic across VM instances, and you get the same, super fast, deployment options (FTP, Git, TFS and Web Deploy) regardless of how many reserved instances you use. With Windows Azure you pay for compute capacity on a per-hour basis – which allows you to scale up and down your resources to match only what you need. Cloud Services and Distributed Caching Windows Azure also supports the ability to build cloud services that support rich multi-tier architectures, automated application management, and scale to extremely large deployments.  Previously we referred to this capability as “hosted services” – with this week’s release we are now referring to this capability as “cloud services”.  We are also enabling a bunch of new features with them. Distributed Cache One of the really cool new features being enabled with cloud services is a new distributed cache capability that enables you to use and setup a low-latency, in-memory distributed cache within your applications.  This cache is isolated for use just by your applications, and does not have any throttling limits. This cache can dynamically grow and shrink elastically (without you have to redeploy your app or make code changes), and supports the full richness of the AppFabric Cache Server API (including regions, high availability, notifications, local cache and more).  In addition to supporting the AppFabric Cache Server API, it also now supports the Memcached protocol – allowing you to point code written against Memcached at it (no code changes required). The new distributed cache can be setup to run in one of two ways: 1) Using a co-located approach.  In this option you allocate a percentage of memory in your existing web and worker roles to be used by the cache, and then the cache joins the memory into one large distributed cache.  Any data put into the cache by one role instance can be accessed by other role instances in your application – regardless of whether the cached data is stored on it or another role.  The big benefit with the “co-located” option is that it is free (you don’t have to pay anything to enable it) and it allows you to use what might have been otherwise unused memory within your application VMs. 2) Alternatively, you can add “cache worker roles” to your cloud service that are used solely for caching.  These will also be joined into one large distributed cache ring that other roles within your application can access.  You can use these roles to cache 10s or 100s of GBs of data in-memory very effectively – and the cache can be elastically increased or decreased at runtime within your application: New SDKs and Tooling Support We have updated all of the Windows Azure SDKs with today’s release to include new features and capabilities.  Our SDKs are now available for multiple languages, and all of the source in them is published under an Apache 2 license and and maintained in GitHub repositories. The .NET SDK for Azure has in particular seen a bunch of great improvements with today’s release, and now includes tooling support for both VS 2010 and the VS 2012 RC. We are also now shipping Windows, Mac and Linux SDK downloads for languages that are offered on all of these systems – allowing developers to develop Windows Azure applications using any development operating system. Much, Much More The above is just a short list of some of the improvements that are shipping in either preview or final form today – there is a LOT more in today’s release.  These include new Virtual Private Networking capabilities, new Service Bus runtime and tooling support, the public preview of the new Azure Media Services, new Data Centers, significantly upgraded network and storage hardware, SQL Reporting Services, new Identity features, support within 40+ new countries and territories, and much, much more. You can learn more about Windows Azure and sign-up to try it for free at http://windowsazure.com.  You can also watch a live keynote I’m giving at 1pm June 7th (later today) where I’ll walk through all of the new features.  We will be opening up the new features I discussed above for public usage a few hours after the keynote concludes.  We are really excited to see the great applications you build with them. Hope this helps, Scott

  Read the article

• JUnit Testing in Multithread Application

  - by e2bady

  This is a problem me and my team faces in almost all of the projects. Testing certain parts of the application with JUnit is not easy and you need to start early and to stick to it, but that's not the question I'm asking. The actual problem is that with n-Threads, locking, possible exceptions within the threads and shared objects the task of testing is not as simple as testing the class, but testing them under endless possible situations within threading. To be more precise, let me tell you about the design of one of our applications: When a user makes a request several threads are started that each analyse a part of the data to complete the analysis, these threads run a certain time depending on the size of the chunk of data (which are endless and of uncertain quality) to analyse, or they may fail if the data was insufficient/lacking quality. After each completed its analysis they call upon a handler which decides after each thread terminates if the collected analysis-data is sufficient to deliver an answer to the request. All of these analysers share certain parts of the applications (some parts because the instances are very big and only a certain number can be loaded into memory and those instances are reusable, some parts because they have a standing connection, where connecting takes time, ex.gr. sql connections) so locking is very common (done with reentrant-locks). While the applications runs very efficient and fast, it's not very easy to test it under real-world conditions. What we do right now is test each class and it's predefined conditions, but there are no automated tests for interlocking and synchronization, which in my opionion is not very good for quality insurances. Given this example how would you handle testing the threading, interlocking and synchronization?

  Read the article

• BizTalk 2009 - Scoped Record Counting in Maps

  - by StuartBrierley

  Within BizTalk there is a functoid called Record Count that will return the number of instances of a repeated record or repeated element that occur in a message instance. The input to this functoid is the record or element to be counted. As an example take the following Source schema, where the Source message has a repeated record called Box and each Box has a repeated element called Item: An instance of this Source schema may look as follows; 2 box records - one with 2 items and one with only 1 item. Our destination schema has a number of elements and a repeated box record.  The top level elements contain totals for the number of boxes and the overall number of items.  Each box record contains a single element representing the number of items in that box. Using the Record Count functoid it is easy to map the top level elements, producing the expected totals of 2 boxes and 3 items: We now need to map the total number of items per box, but how will we do this?  We have already seen that the record count functoid returns the total number of instances for the entire message, and unfortunately it does not allow you to specify a scoping parameter.  In order to acheive Scoped Record Counting we will need to make use of a combination of functoids. As you can see above, by linking to a Logical Existence functoid from the record/element to be counted we can then feed the output into a Value Mapping functoid.  Set the other Value Mapping parameter to "1" and link the output to a Cumulative Sum functoid. Set the other Cumulative Sum functoid parameter to "1" to limit the scope of the Cumulative Sum. This gives us the expected results of Items per Box of 2 and 1 respectively. I ran into this issue with a larger schema on a more complex map, but the eventual solution is still the same.  Hopefully this simplified example will act as a good reminder to me and save someone out there a few minutes of brain scratching.

  Read the article

• Using EC2 instance as main development platform

  - by David

  My problem I am working as a consultant for various companies. Each company provides me with a laptop where with their software on and I also have my own where I have my development environment. I tend to buy a new laptop every second year and find myself spending lots of time configuring and installing software. I also sometimes spend a lot of time waiting for my laptop to process things. To solve all these issues, I am now considering using EC2 (running windows instances) as my main development platform and just access this from any PC I happen to be at. I calculated that running the High-CPU On-Demand Instances (medium) for 8 hours a day for a year costs me 580$, which is acceptable. I imagine that when I approach the workplace each day, I will make a single click my phone to fire up the instance, so it is ready when I get to work. I should have different icons on my phone to fire up the various instance types. The same software should of course automatically be loaded on the various hardware (sometimes I would even need their instance with 68.4 GB of memory). Another advantage is that if I am having a specific problem with my instance, I could fire up another instance and have someone look into the problem and update the image. My question: Does anyone have experience with such a setup on EC2? What kind of problems do you forsee?

  Read the article

• How to get httpd to forward to multiple tomcats for different urls, including / ?

  - by Nick Foote

  Ok So I've got multiple tomcat instances setup on several AJP ports, I also have Apache httpd listening on port 8090 (cos I've got another app already using 8080 at the moment). I've successfully mapped urls such as mydomain.com:8090/demo and mydomain.com:8090/preprod to their respective tomcat instances using Jk Mount and the following vhosts config; <VirtualHost *:8090> JkMount /preprod* preprod JkMount /demo* demo </VirtualHost> But I also want the "root" address to map to another tomcat instance, what will become live/production, ie I want mydomain.com:8090/ to map a 3rd tomcat instance. At the moment nothing happens or changes if I just add to the above config a line; JkMount /* rootwar if I browse to mydomain.com:8090 I just get the same boring apache httpd landing page letting me know its running (ie index.html in httpd/htdocs) Is it possible to use JkMount to redirect the "root" address stuff to a tomcat instance? I can see that a rule like /* will also match URLs like mydomain.com/preprod but I was hoping the rules are applied in order so if /* appears at the end it effectively would be a "if its not one of the other environments, then direct to root/production" Just to be clear I'm trying to setup the following; mydomain.com:8090/preprod --> myApp running in tomcat1 mydomain.com:8090/demo --> myApp running in tomcat2 mydomain.com:8090 --> myApp running in tomcat3

  Read the article

• Object oriented wrapper around a dll

  - by Tom Davies

  So, I'm writing a C# managed wrapper around a native dll. The dll contains several hundred functions. In most cases, the first argument to each function is an opaque handle to a type internal to the dll. So, an obvious starting point for defining some classes in the wrapper would be to define classes corresponding to each of these opaque types, with each instance holding and managing the opaque handle (passed to its constructor) Things are a little awkward when dealing with callbacks from the dll. Naturally, the callback handlers in my wrapper have to be static, but the callbacks arguments invariable contain an opaque handle. In order to get from the static callback back to an object instance, I've created a static dictionary in each class, associating handles with class instances. In the constructor of each class, an entry is put into the dictionary, and this entry is then removed in the Destructors. When I receive a callback, I can then consult the dictionary to retrieve the class instance corresponding to the opaque reference. Are there any obvious flaws to this? Something that seems to be a problem is that the existence static dictionary means that the garbage collector will not act on my class instances that are otherwise unreachable. As they are never garbage collected, they never get removed from the dictionary, so the dictionary grows. It seems I might have to manually dispose of my objects, which is something absolutely would like to avoid. Can anyone suggest a good design that allows me to avoid having to do this?

  Read the article

• BizTalk 2009 - How do I do t"HAT"?

  - by StuartBrierley

  In my previous life working with BizTalk Server 2004, I came to view HAT (the Health and Activity Tracking tool) as one of my first ports of call in the case of problems with any of our BizTalk solutions.  When you move to BizTalk Server 2009 it is quickly apparent that HAT is no longer with us. HAT was useful in BizTalk 2004 mainly as it provided developers and administrators with a number of useful queries and views of what was going on inside BizTalk at runtime; when and what type of messages were received and sent, what messages had been suspended, what orchestration were running or suspended, you could even follow the process flow of a message or orchestration to see what was going on. With BizTalk Server 2009 much of the functionality of HAT can now be found in the BizTalk Administration console.  Select a BizTalk Group and you will be shown the Group Hub Overview page.  This provides a number of default queries that replicate some of those found in the old HAT. You can also use the Group Hub page to create new queries.  These can then be saved and loaded in other Group Hub instances - useful for creating queries in development for later use in Test, Psuedo-Live and Live environments. In the next few posts I am going to look at some of the common queries that we might miss from HAT and recreate them (or something close) using the new query option. Messages - last 100 received Messages - last 100 sent Messages - last 50 suspended Service instances - last 100 I have yet to try the updated Admin-HAT-Console in anger, and after using old-HAT for so long it may take some getting uesd to, but so far I would say that moving the HAT functionality into the BizTalk Administration console was probably the correct way to go.  Having one tool as the place to look for the combined functionality on offer certainly seems to be the sensible option.

  Read the article

• Tomcat + Spring + CI workflow

  - by ex3v

  We're starting our very first project with Spring and java web stack. This project will be mainly about rewriting quite large ERP/CRM from Zend Framework to Java. Important factor in my question is that I come from php territory, where things (in terms of quality) tend to look different than in java world. Fatcs: there will be 2-3 developers, at least one of developers uses Windows, rest uses Linux, there is one remote linux-based machine, which should handle test and production instances, after struggling with buggy legacy code, we want to introduce good programming and development practices (CI, tests, clean code and so on) client: internal, frequent business logic changes, scrum, daily deployments What I want to achieve is good workflow on as many development stages as possible (coding - commiting - testing - deploying). The problem is that I've never done this before, so I don't know what are best practices to do this. What I have so far is: developers code locally, there is vagrant instance on every development machine, managed by puppet. It contains the same linux, jenkins and tomcat versions as production machine, while coding, developer deploys to vagrant machine, after local merge to test branch, jenkins on vagrant handles tests, when everything is fine, developer pushes commits and merges jenkins on remote machine pulls commit from test branch, runs tests and so on, if everything looks green, jenkins deploys to test tomcat instance Deployment to production is manual (altough it can be done using helping scripts) when business logic is tested by other divisions and everything looks fine to client. Now, the real question: does above make any sense? Things that I'm not sure about: Remote machine: won't there be any problems with two (or even three, as jenkins might need one) instances of same app on tomcat? Using vagrant to develop on php environment is just vise. Isn't this overkill while using Tomcat? I mean, is there higher probability that tomcat will act the same on every machine? Is there sense of having local jenkins on vagrant?

  Read the article

• What kind of hosting do I need?

  - by Robert Smith

  I migrated this question from serverfault. Hopefully this is the appropriate place. I have been trying to answer this question but I haven't found an specific answer to my situation. As I want to pay for what I need, I thought I could get a good answer here. I have a custom made forum (rather than a built-in forum like the ones you can find in plugins, e.g. WP-Forum or phpBB type of software) in Django. I don't want to use Apache and modwsgi because it's usually very memory-hungry and I can't afford a big server. I prefer a combination of nginx and gunicorn which I think is very efficient (maybe you can also tell me what you think about that). I'm expecting to receive 10,000 to 20,000 visits each month with 15,000 to 30,000 page impressions. I have reviewed some cloud services like Amazon EC2 or Rackspace and other more traditional services (Linodo). This site won't use videos or big images and I certainly don't need a huge amount of bandwidth (200GB would be definitely too much). I need shell access so shared hosting is out of the question. What do I need to run a website like that without problems? What about RAM? 256MB would be enough (that's the amount of RAM offered by small instances in Amazon and Rackspace)? Do you know of any alternative to those I mentioned? If you need more information to provide a useful answer, please don't hesitate to ask. By the way, I was told that Linodo is not all that different to Amazon EC2 but this website is supposed to work 24/7, so I can't take advantage of Linodo's flexibility regarding creating and deleting instances. Thanks in advance.

  Read the article

• Any danger in using the Wine workaround in 12.04?

  - by TrailRider

  To run certain Windows programs in WINE you need to this workaround: echo 0|sudo tee /proc/sys/kernel/yama/ptrace_scope According to the support websites, this is due to a bug in the Ubuntu kernel that prevents ptrace and WINE playing well together. Using the above command you set the ptrace to 0 which according the research I've done(don't ask me which websites, I have seem a lot of them), ptrace has to do with the interactions between programs. The 0 setting is more permissive than the 1. I have to assume that there was a good reason Ubuntu wanted the ptrace=1 so this leads me back to the short form of the question. Are there any risks involved in setting ptrace=0. Lower security? problems debugging? any others that I haven't thought of??? P.S. for anybody reading this that wonders what the bug causes, the Windows programs will fail to open at all, in the System Monitor you will see many instances of the program trying to open and then they will eventually all quit and if you run the progam for the terminal you will get an error that tells you that the maximum number of program instances has been reached.

  Read the article

• How to enable a Web portal-based rich enterprise platform on different domains and hosts using JS without customization/ server configuration

  - by S.Jalali

  Our company Coscend has built a Web portal-based communications and cloud collaboration platform by using JavaScript (JS), which is embedded in HTML5 and formatted with CSS3. Other technologies used in the core code include Flash, Flex, PostgreSQL and MySQL. Our team would like to host this platform on five different Windows and Linux environments that run different types of Web servers such as IIS and Apache. Technical challenge: Each of these Windows and Linux servers have a different host name and domain name (and IP address), but we would like to keep our enterprise platform independent of host server configuration. Possible approach to solution: We think an API (interface module with a GUI) is needed to accomplish this level of modularity and flexibility while deploying at our enterprise customers. Seeking your insights: In this context, our team would appreciate your guidance on: Is there an algorithmic method to implement this Web portal-based platform in these Windows and Linux environments while separating it from server configuration, i.e., customizing the host name, domain name and IP address for each individual instance? For example, would it be suitable to create some JS variables / objects for host name and domain name and call them in the different implementations? If a reference to the host/domain names occurs on hundreds of portal modules, these variables or JS objects would replace that. If so, what is the best way to make these object modules written in JS portable and re-usable across different environments and instances for enterprise customers? Here is an example of the implemented code for the said platform. The following Web site (www.CoscendCommunications.com) was built using this enterprise collaboration platform and has the base code examples of the platform. This Web site is domain-specific. We like to make the underlying platform such that it is domain and host-independent. This will allow the underlying platform to be deployed in multiple instances of our enterprise customers.

  Read the article

• Could a singleton type replace static methods and classes?

  - by MKO

  In C# Static methods has long served a purpose allowing us to call them without instantiating classes. Only in later year have we became more aware of the problems of using static methods and classes. They can’t use interfaces They can’t use inheritance They are hard to test because you can’t make mocks and stubs Is there a better way ? Obviously we need to be able to access library methods without instantiated classes all the time otherwise our code would become pretty cluttered One possibly solution is to use a new keyword for an old concept: the singleton. Singleton’s are global instances of a class, since they are instances we can use them as we would normal classes. In order to make their use nice and practical we'd need some syntactic sugar however Say that the Math class would be of type singleton instead of an actual class. The actual class containing all the default methods for the Math singleton is DefaultMath, which implements the interface IMath. The singleton would be declared as singleton Math : IMath { public Math { this = new DefaultMath(); } } If we wanted to substitute our own class for all math operations we could make a new class MyMath that inherits DefaultMath, or we could just inherit from the interface IMath and create a whole new Class. To make our class the active Math class, you'd do a simple assignment Math = new MyMath(); and voilá! the next time we call Math.Floor it will call your method. Note that for a normal singleton we'd have to write something like Math.Instance.Floor but the compiler eliminates the need for the Instance property Another idea would be to be able to define a singletons as Lazy so they get instantiated only when they're first called, like lazy singleton Math : IMath What do you think, would it have been a better solution that static methods and classes? Is there any problems with this approach?

  Read the article

• Associate a texture to an object (from a data-model, not graphical point of view).

  - by Raveline

  I'm writing a roguelike where objects and floor can be made of different materials. For instance, let's say we can have a wooden chair, an iron chair, a golden chair, and so on. I've got an Object class (I know, the name is terrible), which is more or less using a composite pattern, and a Material class. Material have different important properties (noise, color...). For the time being, there are 5 different instances of materials, created at the initialization of the game. How would connect an instance of Object with one of the 5 instances of materials ? I see three simple solutions : Using a pointer. Simple and brutal. Using an integer material-id, then get the materials out of a table when engine manipulates the object for various purposes (display, attack analysis, etc.). Not very beautiful, I think, and not very flexible. Using an integer material-id, then get the materials out of a std::map. A bit more flexible, but still not perfect. Do you see other possibilities ? If not, what would you choose (and why) ? Thanks in advance !

  Read the article

• Entity Framework version 1- Brief Synopsis and Tips &ndash; Part 1

  - by Rohit Gupta

  To Do Eager loading use Projections (for e.g. from c in context.Contacts select c, c.Addresses)  or use Include Query Builder Methods (Include(“Addresses”)) If there is multi-level hierarchical Data then to eager load all the relationships use Include Query Builder methods like customers.Include("Order.OrderDetail") to include Order and OrderDetail collections or use customers.Include("Order.OrderDetail.Location") to include all Order, OrderDetail and location collections with a single include statement =========================================================================== If the query uses Joins then Include() Query Builder method will be ignored, use Nested Queries instead If the query does projections then Include() Query Builder method will be ignored Use Address.ContactReference.Load() OR Contact.Addresses.Load() if you need to Deferred Load Specific Entity – This will result in extra round trips to the database ObjectQuery<> cannot return anonymous types... it will return a ObjectQuery<DBDataRecord> Only Include method can be added to Linq Query Methods Any Linq Query method can be added to Query Builder methods. If you need to append a Query Builder Method (other than Include) after a LINQ method  then cast the IQueryable<Contact> to ObjectQuery<Contact> and then append the Query Builder method to it =========================================================================== Query Builder methods are Select, Where, Include Methods which use Entity SQL as parameters e.g. "it.StartDate, it.EndDate" When Query Builder methods do projection then they return ObjectQuery<DBDataRecord>, thus to iterate over this collection use contact.Item[“Name”].ToString() When Linq To Entities methods do projection, they return collection of anonymous types --- thus the collection is strongly typed and supports Intellisense EF Object Context can track changes only on Entities, not on Anonymous types. If you use a Defining Query for a EntitySet then the EntitySet becomes readonly since a Defining Query is the same as a View (which is treated as a ReadOnly by default). However if you want to use this EntitySet for insert/update/deletes then we need to map stored procs (as created in the DB) to the insert/update/delete functions of the Entity in the Designer You can use either Execute method or ToList() method to bind data to datasources/bindingsources If you use the Execute Method then remember that you can traverse through the ObjectResult<> collection (returned by Execute) only ONCE. In WPF use ObservableCollection to bind to data sources , for keeping track of changes and letting EF send updates to the DB automatically. Use Extension Methods to add logic to Entities. For e.g. create extension methods for the EntityObject class. Create a method in ObjectContext Partial class and pass the entity as a parameter, then call this method as desired from within each entity. ================================================================ DefiningQueries and Stored Procedures: For Custom Entities, one can use DefiningQuery or Stored Procedures. Thus the Custom Entity Collection will be populated using the DefiningQuery (of the EntitySet) or the Sproc. If you use Sproc to populate the EntityCollection then the query execution is immediate and this execution happens on the Server side and any filters applied will be applied in the Client App. If we use a DefiningQuery then these queries are composable, meaning the filters (if applied to the entityset) will all be sent together as a single query to the DB, returning only filtered results. If the sproc returns results that cannot be mapped to existing entity, then we first create the Entity/EntitySet in the CSDL using Designer, then create a dummy Entity/EntitySet using XML in the SSDL. When creating a EntitySet in the SSDL for this dummy entity, use a TSQL that does not return any results, but does return the relevant columns e.g. select ContactID, FirstName, LastName from dbo.Contact where 1=2 Also insure that the Entity created in the SSDL uses the SQL DataTypes and not .NET DataTypes. If you are unable to open the EDMX file in the designer then note the Errors ... they will give precise info on what is wrong. The Thrid option is to simply create a Native Query in the SSDL using <Function Name="PaymentsforContact" IsComposable="false">   <CommandText>SELECT ActivityId, Activity AS ActivityName, ImagePath, Category FROM dbo.Activities </CommandText></FuncTion> Then map this Function to a existing Entity. This is a quick way to get a custom Entity which is regular Entity with renamed columns or additional columns (which are computed columns). The disadvantage to using this is that It will return all the rows from the Defining query and any filter (if defined) will be applied only at the Client side (after getting all the rows from DB). If you you DefiningQuery instead then we can use that as a Composable Query. The Fourth option (for mapping a READ stored proc results to a non-existent Entity) is to create a View in the Database which returns all the fields that the sproc also returns, then update the Model so that the model contains this View as a Entity. Then map the Read Sproc to this View Entity. The other option would be to simply create the View and remove the sproc altogether. ================================================================ To Execute a SProc that does not return a entity, use a EntityCommand to execute that proc. You cannot call a sproc FunctionImport that does not return Entities From Code, the only way is to use SSDL function calls using EntityCommand.  This changes with EntityFramework Version 4 where you can return Scalar Types, Complex Types, Entities or NonQuery ================================================================ UDF when created as a Function in SSDL, we need to set the Name & IsComposable properties for the Function element. IsComposable is always false for Sprocs, for UDF's set this to true. You cannot call UDF "Function" from within code since you cannot import a UDF Function into the CSDL Model (with Version 1 of EF). only stored procedures can be imported and then mapped to a entity ================================================================ Entity Framework requires properties that are involved in association mappings to be mapped in all of the function mappings for the entity (Insert, Update and Delete). Because Payment has an association to Reservation... hence we need to pass both the paymentId and reservationId to the Delete sproc even though just the paymentId is the PK on the Payment Table. ================================================================ When mapping insert, update and delete procs to a Entity, insure that all the three or none are mapped. Further if you have a base class and derived class in the CSDL, then you must map (ins, upd, del) sprocs to all parent and child entities in the inheritance relationship. Note that this limitation that base and derived entity methods must all must be mapped does not apply when you are mapping Read Stored Procedures.... ================================================================ You can write stored procedures SQL directly into the SSDL by creating a Function element in the SSDL and then once created, you can map this Function to a CSDL Entity directly in the designer during Function Import ================================================================ You can do Entity Splitting such that One Entity maps to multiple tables in the DB. For e.g. the Customer Entity currently derives from Contact Entity...in addition it also references the ContactPersonalInfo Entity. One can copy all properties from the ContactPersonalInfo Entity into the Customer Entity and then Delete the CustomerPersonalInfo entity, finall one needs to map the copied properties to the ContactPersonalInfo Table in Table Mapping (by adding another table (ContactPersonalInfo) to the Table Mapping... this is called Entity Splitting. Thus now when you insert a Customer record, it will automatically create SQL to insert records into the Contact, Customers and ContactPersonalInfo tables even though you have a Single Entity called Customer in the CSDL =================================================================== There is Table by Type Inheritance where another EDM Entity can derive from another EDM entity and absorb the inherted entities properties, for example in the Break Away Geek Adventures EDM, the Customer entity derives (inherits) from the Contact Entity and absorbs all the properties of Contact entity. Thus when you create a Customer Entity in Code and then call context.SaveChanges the Object Context will first create the TSQL to insert into the Contact Table followed by a TSQL to insert into the Customer table =================================================================== Then there is the Table per Hierarchy Inheritance..... where different types are created based on a condition (similar applying a condition to filter a Entity to contain filtered records)... the diference being that the filter condition populates a new Entity Type (derived from the base Entity). In the BreakAway sample the example is Lodging Entity which is a Abstract Entity and Then Resort and NonResort Entities which derive from Lodging Entity and records are filtered based on the value of the Resort Boolean field =================================================================== Then there is Table per Concrete Type Hierarchy where we create a concrete Entity for each table in the database. In the BreakAway sample there is a entity for the Reservation table and another Entity for the OldReservation table even though both the table contain the same number of fields. The OldReservation Entity can then inherit from the Reservation Entity and configure the OldReservation Entity to remove all Scalar Properties from the Entity (since it inherits the properties from Reservation and filters based on ReservationDate field) =================================================================== Complex Types (Complex Properties) Entities in EF can also contain Complex Properties (in addition to Scalar Properties) and these Complex Properties reference a ComplexType (not a EntityType) DropdownList, ListBox, RadioButtonList, CheckboxList, Bulletedlist are examples of List server controls (not data bound controls) these controls cannot use Complex properties during databinding, they need Scalar Properties. So if a Entity contains Complex properties and you need to bind those to list server controls then use projections to return Scalar properties and bind them to the control (the disadvantage is that projected collections are not tracked by the Object Context and hence cannot persist changes to the projected collections bound to controls) ObjectDataSource and EntityDataSource do account for Complex properties and one can bind entities with Complex Properties to Data Source controls and they will be tracked for changes... with no additional plumbing needed to persist changes to these collections bound to controls So DataBound controls like GridView, FormView need to use EntityDataSource or ObjectDataSource as a datasource for entities that contain Complex properties so that changes to the datasource done using the GridView can be persisted to the DB (enabling the controls for updates)....if you cannot use the EntityDataSource you need to flatten the ComplexType Properties using projections With EF Version 4 ComplexTypes are supported by the Designer and can add/remove/compose Complex Types directly using the Designer =================================================================== Conditional Mapping ... is like Table per Hierarchy Inheritance where Entities inherit from a base class and then used conditions to populate the EntitySet (called conditional Mapping). Conditional Mapping has limitations since you can only use =, is null and IS NOT NULL Conditions to do conditional mapping. If you need more operators for filtering/mapping conditionally then use QueryView(or possibly Defining Query) to create a readonly entity. QueryView are readonly by default... the EntitySet created by the QueryView is enabled for change tracking by the ObjectContext, however the ObjectContext cannot create insert/update/delete TSQL statements for these Entities when SaveChanges is called since it is QueryView. One way to get around this limitation is to map stored procedures for the insert/update/delete operations in the Designer. =================================================================== Difference between QueryView and Defining Query : QueryView is defined in the (MSL) Mapping File/section of the EDM XML, whereas the DefiningQuery is defined in the store schema (SSDL). QueryView is written using Entity SQL and is this database agnostic and can be used against any database/Data Layer. DefiningQuery is written using Database Lanaguage i.e. TSQL or PSQL thus you have more control =================================================================== Performance: Lazy loading is deferred loading done automatically. lazy loading is supported with EF version4 and is on by default. If you need to turn it off then use context.ContextOptions.lazyLoadingEnabled = false To improve Performance consider PreCompiling the ObjectQuery using the CompiledQuery.Compile method

  Read the article

• SQL Server 2012 - AlwaysOn

  - by Claus Jandausch

  Ich war nicht nur irritiert, ich war sogar regelrecht schockiert - und für einen kurzen Moment sprachlos (was nur selten der Fall ist). Gerade eben hatte mich jemand gefragt "Wann Oracle denn etwas Vergleichbares wie AlwaysOn bieten würde - und ob überhaupt?" War ich hier im falschen Film gelandet? Ich konnte nicht anders, als meinen Unmut kundzutun und zu erklären, dass die Fragestellung normalerweise anders herum läuft. Zugegeben - es mag vielleicht strittige Punkte geben im Vergleich zwischen Oracle und SQL Server - bei denen nicht unbedingt immer Oracle die Nase vorn haben muss - aber das Thema Clustering für Hochverfügbarkeit (HA), Disaster Recovery (DR) und Skalierbarkeit gehört mit Sicherheit nicht dazu. Dieses Erlebnis hakte ich am Nachgang als Einzelfall ab, der so nie wieder vorkommen würde. Bis ich kurz darauf eines Besseren belehrt wurde und genau die selbe Frage erneut zu hören bekam. Diesmal sogar im Exadata-Umfeld und einem Oracle Stretch Cluster. Einmal ist keinmal, doch zweimal ist einmal zu viel... Getreu diesem alten Motto war mir klar, dass man das so nicht länger stehen lassen konnte. Ich habe keine Ahnung, wie die Microsoft Marketing Abteilung es geschafft hat, unter dem AlwaysOn Brading eine innovative Technologie vermuten zu lassen - aber sie hat ihren Job scheinbar gut gemacht. Doch abgesehen von einem guten Marketing, stellt sich natürlich die Frage, was wirklich dahinter steckt und wie sich das Ganze mit Oracle vergleichen lässt - und ob überhaupt? Damit wären wir wieder bei der ursprünglichen Frage angelangt.  So viel zum Hintergrund dieses Blogbeitrags - von meiner Antwort handelt der restliche Blog. "Windows was the God ..." Um den wahren Unterschied zwischen Oracle und Microsoft verstehen zu können, muss man zunächst das bedeutendste Microsoft Dogma kennen. Es lässt sich schlicht und einfach auf den Punkt bringen: "Alles muss auf Windows basieren." Die Überschrift dieses Absatzes ist kein von mir erfundener Ausspruch, sondern ein Zitat. Konkret stammt es aus einem längeren Artikel von Kurt Eichenwald in der Vanity Fair aus dem August 2012. Er lautet Microsoft's Lost Decade und sei jedem ans Herz gelegt, der die "Microsoft-Maschinerie" unter Steve Ballmer und einige ihrer Kuriositäten besser verstehen möchte. "YOU TALKING TO ME?" Microsoft C.E.O. Steve Ballmer bei seiner Keynote auf der 2012 International Consumer Electronics Show in Las Vegas am 9. Januar   Manche Dinge in diesem Artikel mögen überspitzt dargestellt erscheinen - sind sie aber nicht. Vieles davon kannte ich bereits aus eigener Erfahrung und kann es nur bestätigen. Anderes hat sich mir erst so richtig erschlossen. Insbesondere die folgenden Passagen führten zum Aha-Erlebnis: “Windows was the god—everything had to work with Windows,” said Stone... “Every little thing you want to write has to build off of Windows (or other existing roducts),” one software engineer said. “It can be very confusing, …” Ich habe immer schon darauf hingewiesen, dass in einem SQL Server Failover Cluster die Microsoft Datenbank eigentlich nichts Nenneswertes zum Geschehen beiträgt, sondern sich voll und ganz auf das Windows Betriebssystem verlässt. Deshalb muss man auch die Windows Server Enterprise Edition installieren, soll ein Failover Cluster für den SQL Server eingerichtet werden. Denn hier werden die Cluster Services geliefert - nicht mit dem SQL Server. Er ist nur lediglich ein weiteres Server Produkt, für das Windows in Ausfallszenarien genutzt werden kann - so wie Microsoft Exchange beispielsweise, oder Microsoft SharePoint, oder irgendein anderes Server Produkt das auf Windows gehostet wird. Auch Oracle kann damit genutzt werden. Das Stichwort lautet hier: Oracle Failsafe. Nur - warum sollte man das tun, wenn gleichzeitig eine überlegene Technologie wie die Oracle Real Application Clusters (RAC) zur Verfügung steht, die dann auch keine Windows Enterprise Edition voraussetzen, da Oracle die eigene Clusterware liefert. Welche darüber hinaus für kürzere Failover-Zeiten sorgt, da diese Cluster-Technologie Datenbank-integriert ist und sich nicht auf "Dritte" verlässt. Wenn man sich also schon keine technischen Vorteile mit einem SQL Server Failover Cluster erkauft, sondern zusätzlich noch versteckte Lizenzkosten durch die Lizenzierung der Windows Server Enterprise Edition einhandelt, warum hat Microsoft dann in den vergangenen Jahren seit SQL Server 2000 nicht ebenfalls an einer neuen und innovativen Lösung gearbeitet, die mit Oracle RAC mithalten kann? Entwickler hat Microsoft genügend? Am Geld kann es auch nicht liegen? Lesen Sie einfach noch einmal die beiden obenstehenden Zitate und sie werden den Grund verstehen. Anders lässt es sich ja auch gar nicht mehr erklären, dass AlwaysOn aus zwei unterschiedlichen Technologien besteht, die beide jedoch wiederum auf dem Windows Server Failover Clustering (WSFC) basieren. Denn daraus ergeben sich klare Nachteile - aber dazu später mehr. Um AlwaysOn zu verstehen, sollte man sich zunächst kurz in Erinnerung rufen, was Microsoft bisher an HA/DR (High Availability/Desaster Recovery) Lösungen für SQL Server zur Verfügung gestellt hat. Replikation Basiert auf logischer Replikation und Pubisher/Subscriber Architektur Transactional Replication Merge Replication Snapshot Replication Microsoft's Replikation ist vergleichbar mit Oracle GoldenGate. Oracle GoldenGate stellt jedoch die umfassendere Technologie dar und bietet High Performance. Log Shipping Microsoft's Log Shipping stellt eine einfache Technologie dar, die vergleichbar ist mit Oracle Managed Recovery in Oracle Version 7. Das Log Shipping besitzt folgende Merkmale: Transaction Log Backups werden von Primary nach Secondary/ies geschickt Einarbeitung (z.B. Restore) auf jedem Secondary individuell Optionale dritte Server Instanz (Monitor Server) für Überwachung und Alarm Log Restore Unterbrechung möglich für Read-Only Modus (Secondary) Keine Unterstützung von Automatic Failover Database Mirroring Microsoft's Database Mirroring wurde verfügbar mit SQL Server 2005, sah aus wie Oracle Data Guard in Oracle 9i, war funktional jedoch nicht so umfassend. Für ein HA/DR Paar besteht eine 1:1 Beziehung, um die produktive Datenbank (Principle DB) abzusichern. Auf der Standby Datenbank (Mirrored DB) werden alle Insert-, Update- und Delete-Operationen nachgezogen. Modi Synchron (High-Safety Modus) Asynchron (High-Performance Modus) Automatic Failover Unterstützt im High-Safety Modus (synchron) Witness Server vorausgesetzt     Zur Frage der Kontinuität Es stellt sich die Frage, wie es um diesen Technologien nun im Zusammenhang mit SQL Server 2012 bestellt ist. Unter Fanfaren seinerzeit eingeführt, war Database Mirroring das erklärte Mittel der Wahl. Ich bin kein Produkt Manager bei Microsoft und kann hierzu nur meine Meinung äußern, aber zieht man den SQL AlwaysOn Team Blog heran, so sieht es nicht gut aus für das Database Mirroring - zumindest nicht langfristig. "Does AlwaysOn Availability Group replace Database Mirroring going forward?” “The short answer is we recommend that you migrate from the mirroring configuration or even mirroring and log shipping configuration to using Availability Group. Database Mirroring will still be available in the Denali release but will be phased out over subsequent releases. Log Shipping will continue to be available in future releases.” Damit wären wir endlich beim eigentlichen Thema angelangt. Was ist eine sogenannte Availability Group und was genau hat es mit der vielversprechend klingenden Bezeichnung AlwaysOn auf sich?   SQL Server 2012 - AlwaysOn Zwei HA-Features verstekcne sich hinter dem “AlwaysOn”-Branding. Einmal das AlwaysOn Failover Clustering aka SQL Server Failover Cluster Instances (FCI) - zum Anderen die AlwaysOn Availability Groups. Failover Cluster Instances (FCI) Entspricht ungefähr dem Stretch Cluster Konzept von Oracle Setzt auf Windows Server Failover Clustering (WSFC) auf Bietet HA auf Instanz-Ebene AlwaysOn Availability Groups (Verfügbarkeitsgruppen) Ähnlich der Idee von Consistency Groups, wie in Storage-Level Replikations-Software von z.B. EMC SRDF Abhängigkeiten zu Windows Server Failover Clustering (WSFC) Bietet HA auf Datenbank-Ebene   Hinweis: Verwechseln Sie nicht eine SQL Server Datenbank mit einer Oracle Datenbank. Und auch nicht eine Oracle Instanz mit einer SQL Server Instanz. Die gleichen Begriffe haben hier eine andere Bedeutung - nicht selten ein Grund, weshalb Oracle- und Microsoft DBAs schnell aneinander vorbei reden. Denken Sie bei einer SQL Server Datenbank eher an ein Oracle Schema, das kommt der Sache näher. So etwas wie die SQL Server Northwind Datenbank ist vergleichbar mit dem Oracle Scott Schema. Wenn Sie die genauen Unterschiede kennen möchten, finden Sie eine detaillierte Beschreibung in meinem Buch "Oracle10g Release 2 für Windows und .NET", erhältich bei Lehmanns, Amazon, etc.   Windows Server Failover Clustering (WSFC) Wie man sieht, basieren beide AlwaysOn Technologien wiederum auf dem Windows Server Failover Clustering (WSFC), um einerseits Hochverfügbarkeit auf Ebene der Instanz zu gewährleisten und andererseits auf der Datenbank-Ebene. Deshalb nun eine kurze Beschreibung der WSFC. Die WSFC sind ein mit dem Windows Betriebssystem geliefertes Infrastruktur-Feature, um HA für Server Anwendungen, wie Microsoft Exchange, SharePoint, SQL Server, etc. zu bieten. So wie jeder andere Cluster, besteht ein WSFC Cluster aus einer Gruppe unabhängiger Server, die zusammenarbeiten, um die Verfügbarkeit einer Applikation oder eines Service zu erhöhen. Falls ein Cluster-Knoten oder -Service ausfällt, kann der auf diesem Knoten bisher gehostete Service automatisch oder manuell auf einen anderen im Cluster verfügbaren Knoten transferriert werden - was allgemein als Failover bekannt ist. Unter SQL Server 2012 verwenden sowohl die AlwaysOn Avalability Groups, als auch die AlwaysOn Failover Cluster Instances die WSFC als Plattformtechnologie, um Komponenten als WSFC Cluster-Ressourcen zu registrieren. Verwandte Ressourcen werden in eine Ressource Group zusammengefasst, die in Abhängigkeit zu anderen WSFC Cluster-Ressourcen gebracht werden kann. Der WSFC Cluster Service kann jetzt die Notwendigkeit zum Neustart der SQL Server Instanz erfassen oder einen automatischen Failover zu einem anderen Server-Knoten im WSFC Cluster auslösen.   Failover Cluster Instances (FCI) Eine SQL Server Failover Cluster Instanz (FCI) ist eine einzelne SQL Server Instanz, die in einem Failover Cluster betrieben wird, der aus mehreren Windows Server Failover Clustering (WSFC) Knoten besteht und so HA (High Availability) auf Ebene der Instanz bietet. Unter Verwendung von Multi-Subnet FCI kann auch Remote DR (Disaster Recovery) unterstützt werden. Eine weitere Option für Remote DR besteht darin, eine unter FCI gehostete Datenbank in einer Availability Group zu betreiben. Hierzu später mehr. FCI und WSFC Basis FCI, das für lokale Hochverfügbarkeit der Instanzen genutzt wird, ähnelt der veralteten Architektur eines kalten Cluster (Aktiv-Passiv). Unter SQL Server 2008 wurde diese Technologie SQL Server 2008 Failover Clustering genannt. Sie nutzte den Windows Server Failover Cluster. In SQL Server 2012 hat Microsoft diese Basistechnologie unter der Bezeichnung AlwaysOn zusammengefasst. Es handelt sich aber nach wie vor um die klassische Aktiv-Passiv-Konfiguration. Der Ablauf im Failover-Fall ist wie folgt: Solange kein Hardware-oder System-Fehler auftritt, werden alle Dirty Pages im Buffer Cache auf Platte geschrieben Alle entsprechenden SQL Server Services (Dienste) in der Ressource Gruppe werden auf dem aktiven Knoten gestoppt Die Ownership der Ressource Gruppe wird auf einen anderen Knoten der FCI transferriert Der neue Owner (Besitzer) der Ressource Gruppe startet seine SQL Server Services (Dienste) Die Connection-Anforderungen einer Client-Applikation werden automatisch auf den neuen aktiven Knoten mit dem selben Virtuellen Network Namen (VNN) umgeleitet Abhängig vom Zeitpunkt des letzten Checkpoints, kann die Anzahl der Dirty Pages im Buffer Cache, die noch auf Platte geschrieben werden müssen, zu unvorhersehbar langen Failover-Zeiten führen. Um diese Anzahl zu drosseln, besitzt der SQL Server 2012 eine neue Fähigkeit, die Indirect Checkpoints genannt wird. Indirect Checkpoints ähnelt dem Fast-Start MTTR Target Feature der Oracle Datenbank, das bereits mit Oracle9i verfügbar war.   SQL Server Multi-Subnet Clustering Ein SQL Server Multi-Subnet Failover Cluster entspricht vom Konzept her einem Oracle RAC Stretch Cluster. Doch dies ist nur auf den ersten Blick der Fall. Im Gegensatz zu RAC ist in einem lokalen SQL Server Failover Cluster jeweils nur ein Knoten aktiv für eine Datenbank. Für die Datenreplikation zwischen geografisch entfernten Sites verlässt sich Microsoft auf 3rd Party Lösungen für das Storage Mirroring.     Die Verbesserung dieses Szenario mit einer SQL Server 2012 Implementierung besteht schlicht darin, dass eine VLAN-Konfiguration (Virtual Local Area Network) nun nicht mehr benötigt wird, so wie dies bisher der Fall war. Das folgende Diagramm stellt dar, wie der Ablauf mit SQL Server 2012 gehandhabt wird. In Site A und Site B wird HA jeweils durch einen lokalen Aktiv-Passiv-Cluster sichergestellt.     Besondere Aufmerksamkeit muss hier der Konfiguration und dem Tuning geschenkt werden, da ansonsten völlig inakzeptable Failover-Zeiten resultieren. Dies liegt darin begründet, weil die Downtime auf Client-Seite nun nicht mehr nur von der reinen Failover-Zeit abhängt, sondern zusätzlich von der Dauer der DNS Replikation zwischen den DNS Servern. (Rufen Sie sich in Erinnerung, dass wir gerade von Multi-Subnet Clustering sprechen). Außerdem ist zu berücksichtigen, wie schnell die Clients die aktualisierten DNS Informationen abfragen. Spezielle Konfigurationen für Node Heartbeat, HostRecordTTL (Host Record Time-to-Live) und Intersite Replication Frequeny für Active Directory Sites und Services werden notwendig. Default TTL für Windows Server 2008 R2: 20 Minuten Empfohlene Einstellung: 1 Minute DNS Update Replication Frequency in Windows Umgebung: 180 Minuten Empfohlene Einstellung: 15 Minuten (minimaler Wert)   Betrachtet man diese Werte, muss man feststellen, dass selbst eine optimale Konfiguration die rigiden SLAs (Service Level Agreements) heutiger geschäftskritischer Anwendungen für HA und DR nicht erfüllen kann. Denn dies impliziert eine auf der Client-Seite erlebte Failover-Zeit von insgesamt 16 Minuten. Hierzu ein Auszug aus der SQL Server 2012 Online Dokumentation: Cons: If a cross-subnet failover occurs, the client recovery time could be 15 minutes or longer, depending on your HostRecordTTL setting and the setting of your cross-site DNS/AD replication schedule.    Wir sind hier an einem Punkt unserer Überlegungen angelangt, an dem sich erklärt, weshalb ich zuvor das "Windows was the God ..." Zitat verwendet habe. Die unbedingte Abhängigkeit zu Windows wird zunehmend zum Problem, da sie die Komplexität einer Microsoft-basierenden Lösung erhöht, anstelle sie zu reduzieren. Und Komplexität ist das Letzte, was sich CIOs heutzutage wünschen.  Zur Ehrenrettung des SQL Server 2012 und AlwaysOn muss man sagen, dass derart lange Failover-Zeiten kein unbedingtes "Muss" darstellen, sondern ein "Kann". Doch auch ein "Kann" kann im unpassenden Moment unvorhersehbare und kostspielige Folgen haben. Die Unabsehbarkeit ist wiederum Ursache vieler an der Implementierung beteiligten Komponenten und deren Abhängigkeiten, wie beispielsweise drei Cluster-Lösungen (zwei von Microsoft, eine 3rd Party Lösung). Wie man die Sache auch dreht und wendet, kommt man an diesem Fakt also nicht vorbei - ganz unabhängig von der Dauer einer Downtime oder Failover-Zeiten. Im Gegensatz zu AlwaysOn und der hier vorgestellten Version eines Stretch-Clusters, vermeidet eine entsprechende Oracle Implementierung eine derartige Komplexität, hervorgerufen duch multiple Abhängigkeiten. Den Unterschied machen Datenbank-integrierte Mechanismen, wie Fast Application Notification (FAN) und Fast Connection Failover (FCF). Für Oracle MAA Konfigurationen (Maximum Availability Architecture) sind Inter-Site Failover-Zeiten im Bereich von Sekunden keine Seltenheit. Wenn Sie dem Link zur Oracle MAA folgen, finden Sie außerdem eine Reihe an Customer Case Studies. Auch dies ist ein wichtiges Unterscheidungsmerkmal zu AlwaysOn, denn die Oracle Technologie hat sich bereits zigfach in höchst kritischen Umgebungen bewährt.   Availability Groups (Verfügbarkeitsgruppen) Die sogenannten Availability Groups (Verfügbarkeitsgruppen) sind - neben FCI - der weitere Baustein von AlwaysOn.   Hinweis: Bevor wir uns näher damit beschäftigen, sollten Sie sich noch einmal ins Gedächtnis rufen, dass eine SQL Server Datenbank nicht die gleiche Bedeutung besitzt, wie eine Oracle Datenbank, sondern eher einem Oracle Schema entspricht. So etwas wie die SQL Server Northwind Datenbank ist vergleichbar mit dem Oracle Scott Schema.   Eine Verfügbarkeitsgruppe setzt sich zusammen aus einem Set mehrerer Benutzer-Datenbanken, die im Falle eines Failover gemeinsam als Gruppe behandelt werden. Eine Verfügbarkeitsgruppe unterstützt ein Set an primären Datenbanken (primäres Replikat) und einem bis vier Sets von entsprechenden sekundären Datenbanken (sekundäre Replikate).       Es können jedoch nicht alle SQL Server Datenbanken einer AlwaysOn Verfügbarkeitsgruppe zugeordnet werden. Der SQL Server Spezialist Michael Otey zählt in seinem SQL Server Pro Artikel folgende Anforderungen auf: Verfügbarkeitsgruppen müssen mit Benutzer-Datenbanken erstellt werden. System-Datenbanken können nicht verwendet werden Die Datenbanken müssen sich im Read-Write Modus befinden. Read-Only Datenbanken werden nicht unterstützt Die Datenbanken in einer Verfügbarkeitsgruppe müssen Multiuser Datenbanken sein Sie dürfen nicht das AUTO_CLOSE Feature verwenden Sie müssen das Full Recovery Modell nutzen und es muss ein vollständiges Backup vorhanden sein Eine gegebene Datenbank kann sich nur in einer einzigen Verfügbarkeitsgruppe befinden und diese Datenbank düerfen nicht für Database Mirroring konfiguriert sein Microsoft empfiehl außerdem, dass der Verzeichnispfad einer Datenbank auf dem primären und sekundären Server identisch sein sollte Wie man sieht, eignen sich Verfügbarkeitsgruppen nicht, um HA und DR vollständig abzubilden. Die Unterscheidung zwischen der Instanzen-Ebene (FCI) und Datenbank-Ebene (Availability Groups) ist von hoher Bedeutung. Vor kurzem wurde mir gesagt, dass man mit den Verfügbarkeitsgruppen auf Shared Storage verzichten könne und dadurch Kosten spart. So weit so gut ... Man kann natürlich eine Installation rein mit Verfügbarkeitsgruppen und ohne FCI durchführen - aber man sollte sich dann darüber bewusst sein, was man dadurch alles nicht abgesichert hat - und dies wiederum für Desaster Recovery (DR) und SLAs (Service Level Agreements) bedeutet. Kurzum, um die Kombination aus beiden AlwaysOn Produkten und der damit verbundene Komplexität kommt man wohl in der Praxis nicht herum.    Availability Groups und WSFC AlwaysOn hängt von Windows Server Failover Clustering (WSFC) ab, um die aktuellen Rollen der Verfügbarkeitsreplikate einer Verfügbarkeitsgruppe zu überwachen und zu verwalten, und darüber zu entscheiden, wie ein Failover-Ereignis die Verfügbarkeitsreplikate betrifft. Das folgende Diagramm zeigt de Beziehung zwischen Verfügbarkeitsgruppen und WSFC:   Der Verfügbarkeitsmodus ist eine Eigenschaft jedes Verfügbarkeitsreplikats. Synychron und Asynchron können also gemischt werden: Availability Modus (Verfügbarkeitsmodus) Asynchroner Commit-Modus Primäres replikat schließt Transaktionen ohne Warten auf Sekundäres Synchroner Commit-Modus Primäres Replikat wartet auf Commit von sekundärem Replikat Failover Typen Automatic Manual Forced (mit möglichem Datenverlust) Synchroner Commit-Modus Geplanter, manueller Failover ohne Datenverlust Automatischer Failover ohne Datenverlust Asynchroner Commit-Modus Nur Forced, manueller Failover mit möglichem Datenverlust   Der SQL Server kennt keinen separaten Switchover Begriff wie in Oracle Data Guard. Für SQL Server werden alle Role Transitions als Failover bezeichnet. Tatsächlich unterstützt der SQL Server keinen Switchover für asynchrone Verbindungen. Es gibt nur die Form des Forced Failover mit möglichem Datenverlust. Eine ähnliche Fähigkeit wie der Switchover unter Oracle Data Guard ist so nicht gegeben.   SQL Sever FCI mit Availability Groups (Verfügbarkeitsgruppen) Neben den Verfügbarkeitsgruppen kann eine zweite Failover-Ebene eingerichtet werden, indem SQL Server FCI (auf Shared Storage) mit WSFC implementiert wird. Ein Verfügbarkeitesreplikat kann dann auf einer Standalone Instanz gehostet werden, oder einer FCI Instanz. Zum Verständnis: Die Verfügbarkeitsgruppen selbst benötigen kein Shared Storage. Diese Kombination kann verwendet werden für lokale HA auf Ebene der Instanz und DR auf Datenbank-Ebene durch Verfügbarkeitsgruppen. Das folgende Diagramm zeigt dieses Szenario:   Achtung! Hier handelt es sich nicht um ein Pendant zu Oracle RAC plus Data Guard, auch wenn das Bild diesen Eindruck vielleicht vermitteln mag - denn alle sekundären Knoten im FCI sind rein passiv. Es existiert außerdem eine weitere und ernsthafte Einschränkung: SQL Server Failover Cluster Instanzen (FCI) unterstützen nicht das automatische AlwaysOn Failover für Verfügbarkeitsgruppen. Jedes unter FCI gehostete Verfügbarkeitsreplikat kann nur für manuelles Failover konfiguriert werden.   Lesbare Sekundäre Replikate Ein oder mehrere Verfügbarkeitsreplikate in einer Verfügbarkeitsgruppe können für den lesenden Zugriff konfiguriert werden, wenn sie als sekundäres Replikat laufen. Dies ähnelt Oracle Active Data Guard, jedoch gibt es Einschränkungen. Alle Abfragen gegen die sekundäre Datenbank werden automatisch auf das Snapshot Isolation Level abgebildet. Es handelt sich dabei um eine Versionierung der Rows. Microsoft versuchte hiermit die Oracle MVRC (Multi Version Read Consistency) nachzustellen. Tatsächlich muss man die SQL Server Snapshot Isolation eher mit Oracle Flashback vergleichen. Bei der Implementierung des Snapshot Isolation Levels handelt sich um ein nachträglich aufgesetztes Feature und nicht um einen inhärenten Teil des Datenbank-Kernels, wie im Falle Oracle. (Ich werde hierzu in Kürze einen weiteren Blogbeitrag verfassen, wenn ich mich mit der neuen SQL Server 2012 Core Lizenzierung beschäftige.) Für die Praxis entstehen aus der Abbildung auf das Snapshot Isolation Level ernsthafte Restriktionen, derer man sich für den Betrieb in der Praxis bereits vorab bewusst sein sollte: Sollte auf der primären Datenbank eine aktive Transaktion zu dem Zeitpunkt existieren, wenn ein lesbares sekundäres Replikat in die Verfügbarkeitsgruppe aufgenommen wird, werden die Row-Versionen auf der korrespondierenden sekundären Datenbank nicht sofort vollständig verfügbar sein. Eine aktive Transaktion auf dem primären Replikat muss zuerst abgeschlossen (Commit oder Rollback) und dieser Transaktions-Record auf dem sekundären Replikat verarbeitet werden. Bis dahin ist das Isolation Level Mapping auf der sekundären Datenbank unvollständig und Abfragen sind temporär geblockt. Microsoft sagt dazu: "This is needed to guarantee that row versions are available on the secondary replica before executing the query under snapshot isolation as all isolation levels are implicitly mapped to snapshot isolation." (SQL Storage Engine Blog: AlwaysOn: I just enabled Readable Secondary but my query is blocked?)  Grundlegend bedeutet dies, dass ein aktives lesbares Replikat nicht in die Verfügbarkeitsgruppe aufgenommen werden kann, ohne das primäre Replikat vorübergehend stillzulegen. Da Leseoperationen auf das Snapshot Isolation Transaction Level abgebildet werden, kann die Bereinigung von Ghost Records auf dem primären Replikat durch Transaktionen auf einem oder mehreren sekundären Replikaten geblockt werden - z.B. durch eine lang laufende Abfrage auf dem sekundären Replikat. Diese Bereinigung wird auch blockiert, wenn die Verbindung zum sekundären Replikat abbricht oder der Datenaustausch unterbrochen wird. Auch die Log Truncation wird in diesem Zustant verhindert. Wenn dieser Zustand längere Zeit anhält, empfiehlt Microsoft das sekundäre Replikat aus der Verfügbarkeitsgruppe herauszunehmen - was ein ernsthaftes Downtime-Problem darstellt. Die Read-Only Workload auf den sekundären Replikaten kann eingehende DDL Änderungen blockieren. Obwohl die Leseoperationen aufgrund der Row-Versionierung keine Shared Locks halten, führen diese Operatioen zu Sch-S Locks (Schemastabilitätssperren). DDL-Änderungen durch Redo-Operationen können dadurch blockiert werden. Falls DDL aufgrund konkurrierender Lese-Workload blockiert wird und der Schwellenwert für 'Recovery Interval' (eine SQL Server Konfigurationsoption) überschritten wird, generiert der SQL Server das Ereignis sqlserver.lock_redo_blocked, welches Microsoft zum Kill der blockierenden Leser empfiehlt. Auf die Verfügbarkeit der Anwendung wird hierbei keinerlei Rücksicht genommen.   Keine dieser Einschränkungen existiert mit Oracle Active Data Guard.   Backups auf sekundären Replikaten  Über die sekundären Replikate können Backups (BACKUP DATABASE via Transact-SQL) nur als copy-only Backups einer vollständigen Datenbank, Dateien und Dateigruppen erstellt werden. Das Erstellen inkrementeller Backups ist nicht unterstützt, was ein ernsthafter Rückstand ist gegenüber der Backup-Unterstützung physikalischer Standbys unter Oracle Data Guard. Hinweis: Ein möglicher Workaround via Snapshots, bleibt ein Workaround. Eine weitere Einschränkung dieses Features gegenüber Oracle Data Guard besteht darin, dass das Backup eines sekundären Replikats nicht ausgeführt werden kann, wenn es nicht mit dem primären Replikat kommunizieren kann. Darüber hinaus muss das sekundäre Replikat synchronisiert sein oder sich in der Synchronisation befinden, um das Beackup auf dem sekundären Replikat erstellen zu können.   Vergleich von Microsoft AlwaysOn mit der Oracle MAA Ich komme wieder zurück auf die Eingangs erwähnte, mehrfach an mich gestellte Frage "Wann denn - und ob überhaupt - Oracle etwas Vergleichbares wie AlwaysOn bieten würde?" und meine damit verbundene (kurze) Irritation. Wenn Sie diesen Blogbeitrag bis hierher gelesen haben, dann kennen Sie jetzt meine darauf gegebene Antwort. Der eine oder andere Punkt traf dabei nicht immer auf Jeden zu, was auch nicht der tiefere Sinn und Zweck meiner Antwort war. Wenn beispielsweise kein Multi-Subnet mit im Spiel ist, sind alle diesbezüglichen Kritikpunkte zunächst obsolet. Was aber nicht bedeutet, dass sie nicht bereits morgen schon wieder zum Thema werden könnten (Sag niemals "Nie"). In manch anderes Fettnäpfchen tritt man wiederum nicht unbedingt in einer Testumgebung, sondern erst im laufenden Betrieb. Erst recht nicht dann, wenn man sich potenzieller Probleme nicht bewusst ist und keine dedizierten Tests startet. Und wer AlwaysOn erfolgreich positionieren möchte, wird auch gar kein Interesse daran haben, auf mögliche Schwachstellen und den besagten Teufel im Detail aufmerksam zu machen. Das ist keine Unterstellung - es ist nur menschlich. Außerdem ist es verständlich, dass man sich in erster Linie darauf konzentriert "was geht" und "was gut läuft", anstelle auf das "was zu Problemen führen kann" oder "nicht funktioniert". Wer will schon der Miesepeter sein? Für mich selbst gesprochen, kann ich nur sagen, dass ich lieber vorab von allen möglichen Einschränkungen wissen möchte, anstelle sie dann nach einer kurzen Zeit der heilen Welt schmerzhaft am eigenen Leib erfahren zu müssen. Ich bin davon überzeugt, dass es Ihnen nicht anders geht. Nachfolgend deshalb eine Zusammenfassung all jener Punkte, die ich im Vergleich zur Oracle MAA (Maximum Availability Architecture) als unbedingt Erwähnenswert betrachte, falls man eine Evaluierung von Microsoft AlwaysOn in Betracht zieht. 1. AlwaysOn ist eine komplexe Technologie Der SQL Server AlwaysOn Stack ist zusammengesetzt aus drei verschiedenen Technlogien: Windows Server Failover Clustering (WSFC) SQL Server Failover Cluster Instances (FCI) SQL Server Availability Groups (Verfügbarkeitsgruppen) Man kann eine derartige Lösung nicht als nahtlos bezeichnen, wofür auch die vielen von Microsoft dargestellten Einschränkungen sprechen. Während sich frühere SQL Server Versionen in Richtung eigener HA/DR Technologien entwickelten (wie Database Mirroring), empfiehlt Microsoft nun die Migration. Doch weshalb dieser Schwenk? Er führt nicht zu einem konsisten und robusten Angebot an HA/DR Technologie für geschäftskritische Umgebungen.  Liegt die Antwort in meiner These begründet, nach der "Windows was the God ..." noch immer gilt und man die Nachteile der allzu engen Kopplung mit Windows nicht sehen möchte? Entscheiden Sie selbst ... 2. Failover Cluster Instanzen - Kein RAC-Pendant Die SQL Server und Windows Server Clustering Technologie basiert noch immer auf dem veralteten Aktiv-Passiv Modell und führt zu einer Verschwendung von Systemressourcen. In einer Betrachtung von lediglich zwei Knoten erschließt sich auf Anhieb noch nicht der volle Mehrwert eines Aktiv-Aktiv Clusters (wie den Real Application Clusters), wie er von Oracle bereits vor zehn Jahren entwickelt wurde. Doch kennt man die Vorzüge der Skalierbarkeit durch einfaches Hinzufügen weiterer Cluster-Knoten, die dann alle gemeinsam als ein einziges logisches System zusammenarbeiten, versteht man was hinter dem Motto "Pay-as-you-Grow" steckt. In einem Aktiv-Aktiv Cluster geht es zwar auch um Hochverfügbarkeit - und ein Failover erfolgt zudem schneller, als in einem Aktiv-Passiv Modell - aber es geht eben nicht nur darum. An dieser Stelle sei darauf hingewiesen, dass die Oracle 11g Standard Edition bereits die Nutzung von Oracle RAC bis zu vier Sockets kostenfrei beinhaltet. Möchten Sie dazu Windows nutzen, benötigen Sie keine Windows Server Enterprise Edition, da Oracle 11g die eigene Clusterware liefert. Sie kommen in den Genuss von Hochverfügbarkeit und Skalierbarkeit und können dazu die günstigere Windows Server Standard Edition nutzen. 3. SQL Server Multi-Subnet Clustering - Abhängigkeit zu 3rd Party Storage Mirroring  Die SQL Server Multi-Subnet Clustering Architektur unterstützt den Aufbau eines Stretch Clusters, basiert dabei aber auf dem Aktiv-Passiv Modell. Das eigentlich Problematische ist jedoch, dass man sich zur Absicherung der Datenbank auf 3rd Party Storage Mirroring Technologie verlässt, ohne Integration zwischen dem Windows Server Failover Clustering (WSFC) und der darunterliegenden Mirroring Technologie. Wenn nun im Cluster ein Failover auf Instanzen-Ebene erfolgt, existiert keine Koordination mit einem möglichen Failover auf Ebene des Storage-Array. 4. Availability Groups (Verfügbarkeitsgruppen) - Vier, oder doch nur Zwei? Ein primäres Replikat erlaubt bis zu vier sekundäre Replikate innerhalb einer Verfügbarkeitsgruppe, jedoch nur zwei im Synchronen Commit Modus. Während dies zwar einen Vorteil gegenüber dem stringenten 1:1 Modell unter Database Mirroring darstellt, fällt der SQL Server 2012 damit immer noch weiter zurück hinter Oracle Data Guard mit bis zu 30 direkten Stanbdy Zielen - und vielen weiteren durch kaskadierende Ziele möglichen. Damit eignet sich Oracle Active Data Guard auch für die Bereitstellung einer Reader-Farm Skalierbarkeit für Internet-basierende Unternehmen. Mit AwaysOn Verfügbarkeitsgruppen ist dies nicht möglich. 5. Availability Groups (Verfügbarkeitsgruppen) - kein asynchrones Switchover  Die Technologie der Verfügbarkeitsgruppen wird auch als geeignetes Mittel für administrative Aufgaben positioniert - wie Upgrades oder Wartungsarbeiten. Man muss sich jedoch einem gravierendem Defizit bewusst sein: Im asynchronen Verfügbarkeitsmodus besteht die einzige Möglichkeit für Role Transition im Forced Failover mit Datenverlust! Um den Verlust von Daten durch geplante Wartungsarbeiten zu vermeiden, muss man den synchronen Verfügbarkeitsmodus konfigurieren, was jedoch ernstzunehmende Auswirkungen auf WAN Deployments nach sich zieht. Spinnt man diesen Gedanken zu Ende, kommt man zu dem Schluss, dass die Technologie der Verfügbarkeitsgruppen für geplante Wartungsarbeiten in einem derartigen Umfeld nicht effektiv genutzt werden kann. 6. Automatisches Failover - Nicht immer möglich Sowohl die SQL Server FCI, als auch Verfügbarkeitsgruppen unterstützen automatisches Failover. Möchte man diese jedoch kombinieren, wird das Ergebnis kein automatisches Failover sein. Denn ihr Zusammentreffen im Failover-Fall führt zu Race Conditions (Wettlaufsituationen), weshalb diese Konfiguration nicht länger das automatische Failover zu einem Replikat in einer Verfügbarkeitsgruppe erlaubt. Auch hier bestätigt sich wieder die tiefere Problematik von AlwaysOn, mit einer Zusammensetzung aus unterschiedlichen Technologien und der Abhängigkeit zu Windows. 7. Problematische RTO (Recovery Time Objective) Microsoft postioniert die SQL Server Multi-Subnet Clustering Architektur als brauchbare HA/DR Architektur. Bedenkt man jedoch die Problematik im Zusammenhang mit DNS Replikation und den möglichen langen Wartezeiten auf Client-Seite von bis zu 16 Minuten, sind strenge RTO Anforderungen (Recovery Time Objectives) nicht erfüllbar. Im Gegensatz zu Oracle besitzt der SQL Server keine Datenbank-integrierten Technologien, wie Oracle Fast Application Notification (FAN) oder Oracle Fast Connection Failover (FCF). 8. Problematische RPO (Recovery Point Objective) SQL Server ermöglicht Forced Failover (erzwungenes Failover), bietet jedoch keine Möglichkeit zur automatischen Übertragung der letzten Datenbits von einem alten zu einem neuen primären Replikat, wenn der Verfügbarkeitsmodus asynchron war. Oracle Data Guard hingegen bietet diese Unterstützung durch das Flush Redo Feature. Dies sichert "Zero Data Loss" und beste RPO auch in erzwungenen Failover-Situationen. 9. Lesbare Sekundäre Replikate mit Einschränkungen Aufgrund des Snapshot Isolation Transaction Level für lesbare sekundäre Replikate, besitzen diese Einschränkungen mit Auswirkung auf die primäre Datenbank. Die Bereinigung von Ghost Records auf der primären Datenbank, wird beeinflusst von lang laufenden Abfragen auf der lesabaren sekundären Datenbank. Die lesbare sekundäre Datenbank kann nicht in die Verfügbarkeitsgruppe aufgenommen werden, wenn es aktive Transaktionen auf der primären Datenbank gibt. Zusätzlich können DLL Änderungen auf der primären Datenbank durch Abfragen auf der sekundären blockiert werden. Und imkrementelle Backups werden hier nicht unterstützt.   Keine dieser Restriktionen existiert unter Oracle Data Guard.

  Read the article

• C#/.NET Little Wonders: The EventHandler and EventHandler&lt;TEventArgs&gt; delegates

  - by James Michael Hare

  Once again, in this series of posts I look at the parts of the .NET Framework that may seem trivial, but can help improve your code by making it easier to write and maintain. The index of all my past little wonders posts can be found here. In the last two weeks, we examined the Action family of delegates (and delegates in general), and the Func family of delegates and how they can be used to support generic, reusable algorithms and classes. So this week, we are going to look at a handy pair of delegates that can be used to eliminate the need for defining custom delegates when creating events: the EventHandler and EventHandler<TEventArgs> delegates. Events and delegates Before we begin, let’s quickly consider events in .NET.  According to the MSDN: An event in C# is a way for a class to provide notifications to clients of that class when some interesting thing happens to an object. So, basically, you can create an event in a type so that users of that type can subscribe to notifications of things of interest.  How is this different than some of the delegate programming that we talked about in the last two weeks?  Well, you can think of an event as a special access modifier on a delegate.  Some differences between the two are: Events are a special access case of delegates They behave much like delegates instances inside the type they are declared in, but outside of that type they can only be (un)subscribed to. Events can specify add/remove behavior explicitly If you want to do additional work when someone subscribes or unsubscribes to an event, you can specify the add and remove actions explicitly. Events have access modifiers, but these only specify the access level of those who can (un)subscribe A public event, for example, means anyone can (un)subscribe, but it does not mean that anyone can raise (invoke) the event directly.  Events can only be raised by the type that contains them In contrast, if a delegate is visible, it can be invoked outside of the object (not even in a sub-class!). Events tend to be for notifications only, and should be treated as optional Semantically speaking, events typically don’t perform work on the the class directly, but tend to just notify subscribers when something of note occurs. My basic rule-of-thumb is that if you are just wanting to notify any listeners (who may or may not care) that something has happened, use an event.  However, if you want the caller to provide some function to perform to direct the class about how it should perform work, make it a delegate. Declaring events using custom delegates To declare an event in a type, we simply use the event keyword and specify its delegate type.  For example, let’s say you wanted to create a new TimeOfDayTimer that triggers at a given time of the day (as opposed to on an interval).  We could write something like this: 1: public delegate void TimeOfDayHandler(object source, ElapsedEventArgs e); 2:  3: // A timer that will fire at time of day each day. 4: public class TimeOfDayTimer : IDisposable 5: { 6: // Event that is triggered at time of day. 7: public event TimeOfDayHandler Elapsed; 8:  9: // ... 10: } The first thing to note is that the event is a delegate type, which tells us what types of methods may subscribe to it.  The second thing to note is the signature of the event handler delegate, according to the MSDN: The standard signature of an event handler delegate defines a method that does not return a value, whose first parameter is of type Object and refers to the instance that raises the event, and whose second parameter is derived from type EventArgs and holds the event data. If the event does not generate event data, the second parameter is simply an instance of EventArgs. Otherwise, the second parameter is a custom type derived from EventArgs and supplies any fields or properties needed to hold the event data. So, in a nutshell, the event handler delegates should return void and take two parameters: An object reference to the object that raised the event. An EventArgs (or a subclass of EventArgs) reference to event specific information. Even if your event has no additional information to provide, you are still expected to provide an EventArgs instance.  In this case, feel free to pass the EventArgs.Empty singleton instead of creating new instances of EventArgs (to avoid generating unneeded memory garbage). The EventHandler delegate Because many events have no additional information to pass, and thus do not require custom EventArgs, the signature of the delegates for subscribing to these events is typically: 1: // always takes an object and an EventArgs reference 2: public delegate void EventHandler(object sender, EventArgs e) It would be insane to recreate this delegate for every class that had a basic event with no additional event data, so there already exists a delegate for you called EventHandler that has this very definition!  Feel free to use it to define any events which supply no additional event information: 1: public class Cache 2: { 3: // event that is raised whenever the cache performs a cleanup 4: public event EventHandler OnCleanup; 5:  6: // ... 7: } This will handle any event with the standard EventArgs (no additional information).  But what of events that do need to supply additional information?  Does that mean we’re out of luck for subclasses of EventArgs?  That’s where the generic for of EventHandler comes into play… The generic EventHandler<TEventArgs> delegate Starting with the introduction of generics in .NET 2.0, we have a generic delegate called EventHandler<TEventArgs>.  Its signature is as follows: 1: public delegate void EventHandler<TEventArgs>(object sender, TEventArgs e) 2: where TEventArgs : EventArgs This is similar to EventHandler except it has been made generic to support the more general case.  Thus, it will work for any delegate where the first argument is an object (the sender) and the second argument is a class derived from EventArgs (the event data). For example, let’s say we wanted to create a message receiver, and we wanted it to have a few events such as OnConnected that will tell us when a connection is established (probably with no additional information) and OnMessageReceived that will tell us when a new message arrives (probably with a string for the new message text). So for OnMessageReceived, our MessageReceivedEventArgs might look like this: 1: public sealed class MessageReceivedEventArgs : EventArgs 2: { 3: public string Message { get; set; } 4: } And since OnConnected needs no event argument type defined, our class might look something like this: 1: public class MessageReceiver 2: { 3: // event that is called when the receiver connects with sender 4: public event EventHandler OnConnected; 5:  6: // event that is called when a new message is received. 7: public event EventHandler<MessageReceivedEventArgs> OnMessageReceived; 8:  9: // ... 10: } Notice, nowhere did we have to define a delegate to fit our event definition, the EventHandler and generic EventHandler<TEventArgs> delegates fit almost anything we’d need to do with events. Sidebar: Thread-safety and raising an event When the time comes to raise an event, we should always check to make sure there are subscribers, and then only raise the event if anyone is subscribed.  This is important because if no one is subscribed to the event, then the instance will be null and we will get a NullReferenceException if we attempt to raise the event. 1: // This protects against NullReferenceException... or does it? 2: if (OnMessageReceived != null) 3: { 4: OnMessageReceived(this, new MessageReceivedEventArgs(aMessage)); 5: } The above code seems to handle the null reference if no one is subscribed, but there’s a problem if this is being used in multi-threaded environments.  For example, assume we have thread A which is about to raise the event, and it checks and clears the null check and is about to raise the event.  However, before it can do that thread B unsubscribes to the event, which sets the delegate to null.  Now, when thread A attempts to raise the event, this causes the NullReferenceException that we were hoping to avoid! To counter this, the simplest best-practice method is to copy the event (just a multicast delegate) to a temporary local variable just before we raise it.  Since we are inside the class where this event is being raised, we can copy it to a local variable like this, and it will protect us from multi-threading since multicast delegates are immutable and assignments are atomic: 1: // always make copy of the event multi-cast delegate before checking 2: // for null to avoid race-condition between the null-check and raising it. 3: var handler = OnMessageReceived; 4: 5: if (handler != null) 6: { 7: handler(this, new MessageReceivedEventArgs(aMessage)); 8: } The very slight trade-off is that it’s possible a class may get an event after it unsubscribes in a multi-threaded environment, but this is a small risk and classes should be prepared for this possibility anyway.  For a more detailed discussion on this, check out this excellent Eric Lippert blog post on Events and Races. Summary Generic delegates give us a lot of power to make generic algorithms and classes, and the EventHandler delegate family gives us the flexibility to create events easily, without needing to redefine delegates over and over.  Use them whenever you need to define events with or without specialized EventArgs.   Tweet Technorati Tags: .NET, C#, CSharp, Little Wonders, Generics, Delegates, EventHandler

  Read the article

• How can I optimize this subqueried and Joined MySQL Query?

  - by kevzettler

  I'm pretty green on mysql and I need some tips on cleaning up a query. It is used in several variations through out a site. Its got some subquerys derived tables and fun going on. Heres the query: # Query_time: 2 Lock_time: 0 Rows_sent: 0 Rows_examined: 0 SELECT * FROM ( SELECT products . *, categories.category_name AS category, ( SELECT COUNT( * ) FROM distros WHERE distros.product_id = products.product_id) AS distro_count, (SELECT COUNT(*) FROM downloads WHERE downloads.product_id = products.product_id AND WEEK(downloads.date) = WEEK(curdate())) AS true_downloads, (SELECT COUNT(*) FROM views WHERE views.product_id = products.product_id AND WEEK(views.date) = WEEK(curdate())) AS true_views FROM products INNER JOIN categories ON products.category_id = categories.category_id ORDER BY created_date DESC, true_views DESC ) AS count_table WHERE count_table.distro_count > 0 AND count_table.status = 'published' AND count_table.active = 1 LIMIT 0, 8 Heres the explain: +----+--------------------+------------+-------+---------------+-------------+---------+------------------------------------+------+----------------------------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+--------------------+------------+-------+---------------+-------------+---------+------------------------------------+------+----------------------------------------------+ | 1 | PRIMARY | <derived2> | ALL | NULL | NULL | NULL | NULL | 232 | Using where | | 2 | DERIVED | categories | index | PRIMARY | idx_name | 47 | NULL | 13 | Using index; Using temporary; Using filesort | | 2 | DERIVED | products | ref | category_id | category_id | 4 | digizald_db.categories.category_id | 9 | | | 5 | DEPENDENT SUBQUERY | views | ref | product_id | product_id | 4 | digizald_db.products.product_id | 46 | Using where | | 4 | DEPENDENT SUBQUERY | downloads | ref | product_id | product_id | 4 | digizald_db.products.product_id | 14 | Using where | | 3 | DEPENDENT SUBQUERY | distros | ref | product_id | product_id | 4 | digizald_db.products.product_id | 1 | Using index | +----+--------------------+------------+-------+---------------+-------------+---------+------------------------------------+------+----------------------------------------------+ 6 rows in set (0.04 sec) And the Tables: mysql> describe products; +---------------+--------------------------------------------------+------+-----+-------------------+----------------+ | Field | Type | Null | Key | Default | Extra | +---------------+--------------------------------------------------+------+-----+-------------------+----------------+ | product_id | int(10) unsigned | NO | PRI | NULL | auto_increment | | product_key | char(32) | NO | | NULL | | | title | varchar(150) | NO | | NULL | | | company | varchar(150) | NO | | NULL | | | user_id | int(10) unsigned | NO | MUL | NULL | | | description | text | NO | | NULL | | | video_code | text | NO | | NULL | | | category_id | int(10) unsigned | NO | MUL | NULL | | | price | decimal(10,2) | NO | | NULL | | | quantity | int(10) unsigned | NO | | NULL | | | downloads | int(10) unsigned | NO | | NULL | | | views | int(10) unsigned | NO | | NULL | | | status | enum('pending','published','rejected','removed') | NO | | NULL | | | active | tinyint(1) | NO | | NULL | | | deleted | tinyint(1) | NO | | NULL | | | created_date | datetime | NO | | NULL | | | modified_date | timestamp | NO | | CURRENT_TIMESTAMP | | | scrape_source | varchar(215) | YES | | NULL | | +---------------+--------------------------------------------------+------+-----+-------------------+----------------+ 18 rows in set (0.00 sec) mysql> describe categories -> ; +------------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------------+------------------+------+-----+---------+----------------+ | category_id | int(10) unsigned | NO | PRI | NULL | auto_increment | | category_name | varchar(45) | NO | MUL | NULL | | | parent_id | int(10) unsigned | YES | MUL | NULL | | | category_type_id | int(10) unsigned | NO | | NULL | | +------------------+------------------+------+-----+---------+----------------+ 4 rows in set (0.00 sec) mysql> describe compatibilities -> ; +------------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------------+------------------+------+-----+---------+----------------+ | compatibility_id | int(10) unsigned | NO | PRI | NULL | auto_increment | | name | varchar(45) | NO | | NULL | | | code_name | varchar(45) | NO | | NULL | | | description | varchar(128) | NO | | NULL | | | position | int(10) unsigned | NO | | NULL | | +------------------+------------------+------+-----+---------+----------------+ 5 rows in set (0.01 sec) mysql> describe distros -> ; +------------------+--------------------------------------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------------+--------------------------------------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | product_id | int(10) unsigned | NO | MUL | NULL | | | compatibility_id | int(10) unsigned | NO | MUL | NULL | | | user_id | int(10) unsigned | NO | | NULL | | | status | enum('pending','published','rejected','removed') | NO | | NULL | | | distro_type | enum('file','url') | NO | | NULL | | | version | varchar(150) | NO | | NULL | | | filename | varchar(50) | YES | | NULL | | | url | varchar(250) | YES | | NULL | | | virus | enum('READY','PASS','FAIL') | YES | | NULL | | | downloads | int(10) unsigned | NO | | 0 | | +------------------+--------------------------------------------------+------+-----+---------+----------------+ 11 rows in set (0.01 sec) mysql> describe downloads; +------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------+------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | product_id | int(10) unsigned | NO | MUL | NULL | | | distro_id | int(10) unsigned | NO | MUL | NULL | | | user_id | int(10) unsigned | NO | MUL | NULL | | | ip_address | varchar(15) | NO | | NULL | | | date | datetime | NO | | NULL | | +------------+------------------+------+-----+---------+----------------+ 6 rows in set (0.01 sec) mysql> describe views -> ; +------------+------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------+------------------+------+-----+---------+----------------+ | id | int(10) unsigned | NO | PRI | NULL | auto_increment | | product_id | int(10) unsigned | NO | MUL | NULL | | | user_id | int(10) unsigned | NO | MUL | NULL | | | ip_address | varchar(15) | NO | | NULL | | | date | datetime | NO | | NULL | | +------------+------------------+------+-----+---------+----------------+ 5 rows in set (0.00 sec)

  Read the article

• Refactoring a leaf class to a base class, and keeping it also a interface implementation

  - by elcuco

  I am trying to refactor a working code. The code basically derives an interface class into a working implementation, and I want to use this implementation outside the original project as a standalone class. However, I do not want to create a fork, and I want the original project to be able to take out their implementation, and use mine. The problem is that the hierarchy structure is very different and I am not sure if this would work. I also cannot use the original base class in my project, since in reality it's quite entangled in the project (too many classes, includes) and I need to take care of only a subdomain of the problems the original project is. I wrote this code to test an idea how to implement this, and while it's working, I am not sure I like it: #include <iostream> // Original code is: // IBase -> Derived1 // I need to refactor Derive2 to be both indipendet class // and programmers should also be able to use the interface class // Derived2 -> MyClass + IBase // MyClass class IBase { public: virtual void printMsg() = 0; }; /////////////////////////////////////////////////// class Derived1 : public IBase { public: virtual void printMsg(){ std::cout << "Hello from Derived 1" << std::endl; } }; ////////////////////////////////////////////////// class MyClass { public: virtual void printMsg(){ std::cout << "Hello from MyClass" << std::endl; } }; class Derived2: public IBase, public MyClass{ virtual void printMsg(){ MyClass::printMsg(); } }; class Derived3: public MyClass, public IBase{ virtual void printMsg(){ MyClass::printMsg(); } }; int main() { IBase *o1 = new Derived1(); IBase *o2 = new Derived2(); IBase *o3 = new Derived3(); MyClass *o4 = new MyClass(); o1->printMsg(); o2->printMsg(); o3->printMsg(); o4->printMsg(); return 0; } The output is working as expected (tested using gcc and clang, 2 different C++ implementations so I think I am safe here): [elcuco@pinky ~/src/googlecode/qtedit4/tools/qtsourceview/qate/tests] ./test1 Hello from Derived 1 Hello from MyClass Hello from MyClass Hello from MyClass [elcuco@pinky ~/src/googlecode/qtedit4/tools/qtsourceview/qate/tests] ./test1.clang Hello from Derived 1 Hello from MyClass Hello from MyClass Hello from MyClass The question is My original code was: class Derived3: public MyClass, public IBase{ virtual void IBase::printMsg(){ MyClass::printMsg(); } }; Which is what I want to express, but this does not compile. I must admit I do not fully understand why this code work, as I expect that the new method Derived3::printMsg() will be an implementation of MyClass::printMsg() and not IBase::printMsg() (even tough this is what I do want). How does the compiler chooses which method to re-implement, when two "sister classes" have the same virtual function name? If anyone has a better way of implementing this, I would like to know as well :)

  Read the article

• Can't display Tool Tips in VC++6.0

  - by Paul

  I'm missing something fundamental, and probably both simple and obvious. My issue: I have a view (CPlaybackView, derived from CView). The view displays a bunch of objects derived from CRectTracker (CMpRectTracker). These objects each contain a floating point member. I want to display that floating point member when the mouse hovers over the CMpRectTracker. The handler method is never executed, although I can trace through OnIntitialUpdate, PreTranslateMessage, and OnMouseMove. This is in Visual C++ v. 6.0. Here's what I've done to try to accomplish this: 1. In the view's header file: public: BOOL OnToolTipNeedText(UINT id, NMHDR * pNMHDR, LRESULT * pResult); private: CToolTipCtrl m_ToolTip; CMpRectTracker *m_pCurrentRectTracker;//Derived from CRectTracker 2. In the view's implementation file: a. In Message Map: ON_NOTIFY_EX(TTN_NEEDTEXT,0,OnToolTipNeedText) b. In CPlaybackView::OnInitialUpdate: if (m_ToolTip.Create(this, TTS_ALWAYSTIP) && m_ToolTip.AddTool(this)) { m_ToolTip.SendMessage(TTM_SETMAXTIPWIDTH, 0, SHRT_MAX); m_ToolTip.SendMessage(TTM_SETDELAYTIME, TTDT_AUTOPOP, SHRT_MAX); m_ToolTip.SendMessage(TTM_SETDELAYTIME, TTDT_INITIAL, 200); m_ToolTip.SendMessage(TTM_SETDELAYTIME, TTDT_RESHOW, 200); } else { TRACE("Error in creating ToolTip"); } this->EnableToolTips(); c. In CPlaybackView::OnMouseMove: if (::IsWindow(m_ToolTip.m_hWnd)) { m_pCurrentRectTracker = NULL; m_ToolTip.Activate(FALSE); if(m_rtMilepostRect.HitTest(point) >= 0) { POSITION pos = pDoc->m_rtMilepostList.GetHeadPosition(); while(pos) { CMpRectTracker tracker = pDoc->m_rtMilepostList.GetNext(pos); if(tracker.HitTest(point) >= 0) { m_pCurrentRectTracker = &tracker; m_ToolTip.Activate(TRUE); break; } } } } d. In CPlaybackView::PreTranslateMessage: if (::IsWindow(m_ToolTip.m_hWnd) && pMsg->hwnd == m_hWnd) { switch(pMsg->message) { case WM_LBUTTONDOWN: case WM_MOUSEMOVE: case WM_LBUTTONUP: case WM_RBUTTONDOWN: case WM_MBUTTONDOWN: case WM_RBUTTONUP: case WM_MBUTTONUP: m_ToolTip.RelayEvent(pMsg); break; } } e. Finally, the handler method: BOOL CPlaybackView::OnToolTipNeedText(UINT id, NMHDR * pNMHDR, LRESULT * pResult) { BOOL bHandledNotify = FALSE; CPoint CursorPos; VERIFY(::GetCursorPos(&CursorPos)); ScreenToClient(&CursorPos); CRect ClientRect; GetClientRect(ClientRect); // Make certain that the cursor is in the client rect, because the // mainframe also wants these messages to provide tooltips for the // toolbar. if (ClientRect.PtInRect(CursorPos)) { TOOLTIPTEXT *pTTT = (TOOLTIPTEXT *)pNMHDR; CString str; str.Format("%f", m_pCurrentRectTracker->GetMilepost()); ASSERT(str.GetLength() < sizeof(pTTT->szText)); ::strcpy(pTTT->szText, str); bHandledNotify = TRUE; } return bHandledNotify; }

  Read the article

• Scripting out Contained Database Users

  - by Argenis

    Today’s blog post comes from a Twitter thread on which @SQLSoldier, @sqlstudent144 and @SQLTaiob were discussing the internals of contained database users. Unless you have been living under a rock, you’ve heard about the concept of contained users within a SQL Server database (hit the link if you have not). In this article I’d like to show you that you can, indeed, script out contained database users and recreate them on another database, as either contained users or as good old fashioned logins/server principals as well. Why would this be useful? Well, because you would not need to know the password for the user in order to recreate it on another instance. I know there is a limited number of scenarios where this would be necessary, but nonetheless I figured I’d throw this blog post to show how it can be done. A more obscure use case: with the password hash (which I’m about to show you how to obtain) you could also crack the password using a utility like hashcat, as highlighted on this SQLServerCentral article. The Investigation SQL Server uses System Base Tables to save the password hashes of logins and contained database users. For logins it uses sys.sysxlgns, whereas for contained database users it leverages sys.sysowners. I’ll show you what I do to figure this stuff out: I create a login/contained user, and then I immediately browse the transaction log with, for example, fn_dblog. It’s pretty obvious that only two base tables touched by the operation are sys.sysxlgns, and also sys.sysprivs – the latter is used to track permissions. If I connect to the DAC on my instance, I can query for the password hash of this login I’ve just created. A few interesting things about this hash. This was taken on my laptop, and I happen to be running SQL Server 2014 RTM CU2, which is the latest public build of SQL Server 2014 as of time of writing. In 2008 R2 and prior versions (back to 2000), the password hashes would start with 0x0100. The reason why this changed is because starting with SQL Server 2012 password hashes are kept using a SHA512 algorithm, as opposed to SHA-1 (used since 2000) or Snefru (used in 6.5 and 7.0). SHA-1 is nowadays deemed unsafe and is very easy to crack. For regular SQL logins, this information is exposed through the sys.sql_logins catalog view, so there is really no need to connect to the DAC to grab an SID/password hash pair. For contained database users, there is (currently) no method of obtaining SID or password hashes without connecting to the DAC. If we create a contained database user, this is what we get from the transaction log: Note that the System Base Table used in this case is sys.sysowners. sys.sysprivs is used as well, and again this is to track permissions. To query sys.sysowners, you would have to connect to the DAC, as I mentioned previously. And this is what you would get: There are other ways to figure out what SQL Server uses under the hood to store contained database user password hashes, like looking at the execution plan for a query to sys.dm_db_uncontained_entities (Thanks, Robert Davis!) SIDs, Logins, Contained Users, and Why You Care…Or Not. One of the reasons behind the existence of Contained Users was the concept of portability of databases: it is really painful to maintain Server Principals (Logins) synced across most shared-nothing SQL Server HA/DR technologies (Mirroring, Availability Groups, and Log Shipping). Often times you would need the Security Identifier (SID) of these logins to match across instances, and that meant that you had to fetch whatever SID was assigned to the login on the principal instance so you could recreate it on a secondary. With contained users you normally wouldn’t care about SIDs, as the users are always available (and synced, as long as synchronization takes place) across instances. Now you might be presented some particular requirement that might specify that SIDs synced between logins on certain instances and contained database users on other databases. How would you go about creating a contained database user with a specific SID? The answer is that you can’t do it directly, but there’s a little trick that would allow you to do it. Create a login with a specified SID and password hash, create a user for that server principal on a partially contained database, then migrate that user to contained using the system stored procedure sp_user_migrate_to_contained, then drop the login. CREATE LOGIN <login_name> WITH PASSWORD = <password_hash> HASHED, SID = <sid> ; GO USE <partially_contained_db>; GO CREATE USER <user_name> FROM LOGIN <login_name>; GO EXEC sp_migrate_user_to_contained @username = <user_name>, @rename = N’keep_name’, @disablelogin = N‘disable_login’; GO DROP LOGIN <login_name>; GO Here’s how this skeleton would look like in action: And now I have a contained user with a specified SID and password hash. In my example above, I renamed the user after migrated it to contained so that it is, hopefully, easier to understand. Enjoy!

  Read the article

• Announcing the New Windows Azure Web Sites Shared Scaling Tier

  - by Clint Edmonson

  Windows Azure Web Sites has added a new pricing tier that will solve the #1 blocker for the web development community. The shared tier now supports custom domain names mapped to shared-instance web sites. This post will outline the plan changes and elaborate on how the new pricing model makes Windows Azure Web Sites an even richer option for web development shops of all sizes. Free Shared Reserved # of Sites 10 100 100 Egress 165MB/Day 5GB/Month Included 5GB/Month Included Storage 1GB 1GB 10GB Throttling CPU/Memory/Egress CPU/Memory Unlimited Price Free $.02/hr per site, per instance $.08/hr per core Setting the Stage In June, we released the first public preview of Windows Azure Web Sites, which gave web developers a great platform on which to get web sites running using their web development framework of choice. PHP, Node.js, classic ASP, and ASP.NET developers can all utilize the Windows Azure platform to create and launch their web sites. Likewise, these developers have a series of data storage options using Windows Azure SQL Databases, MySQL, or Windows Azure Storage. The Windows Azure Web Sites free offer enabled startups to get their site up and running on Windows Azure with a minimal investment, and with multiple deployment and continuous integration features such as Git, Team Foundation Services, FTP, and Web Deploy.  The response to the Windows Azure Web Sites offer has been overwhelmingly positive. Since the addition of the service on June 12th, tens of thousands of web sites have been deployed to Windows Azure and the volume of adoption is increasing every week. Preview Feedback In spite of the growth and success of the product, the community has had questions about features lacking in the free preview offer. The main question web developers asked regarding Windows Azure Web Sites relates to the lack of the free offer’s support for domain name mapping. During the preview launch period, customer feedback made it obvious that the lack of domain name mapping support was an area of concern. We’re happy to announce that this #1 request has been delivered as a feature of the new shared plan. New Shared Tier Portal Features In the screen shot below, the “Scale” tab in the portal shows the new tiers – Free, Shared, and Reserved – and gives the user the ability to quickly move any of their free web sites into the shared tier. With a single mouse-click, the user can move their site into the shared tier. Once a site has been moved into the shared tier, a new Manage Domains button appears in the bottom action bar of the Windows Azure Portal giving site owners the ability to manage their domain names for a shared site. This button brings up the domain-management dialog, which can be used to enter in a specific domain name that will be mapped to the Windows Azure Web Site. Shared Tier Benefits Startups and large web agencies will both benefit from this plan change. Here are a few examples of scenarios which fit the new pricing model: Startups no longer have to select the reserved plan to map domain names to their sites. Instead, they can use the free option to develop their sites and choose on a site-by-site basis which sites they elect to move into the shared plan, paying only for the sites that are finished and ready to be domain-mapped Agencies who manage dozens of sites will realize a lower cost of ownership over the long term by moving their sites into reserved mode. Once multi-site companies reach a certain price point in the shared tier, it is much more cost-effective to move sites to a reserved tier.  Long-term, it’s easy to see how the new Windows Azure Web Sites shared pricing tier makes Windows Azure Web Sites it a great choice for both startups and agency customers, as it enables rapid growth and upgrades while keeping the cost to a minimum. Large agencies will be able to have all of their sites in their own instances, and startups will have the capability to scale up to multiple-shared instances for minimal cost and eventually move to reserved instances without worrying about the need to incur continually additional costs. Customers can feel confident they have the power of the Microsoft Windows Azure brand and our world-class support, at prices competitive in the market. Plus, in addition to realizing the cost savings, they’ll have the whole family of Windows Azure features available. Continuous Deployment from GitHub and CodePlex Along with this new announcement are two other exciting new features. I’m proud to announce that web developers can now publish their web sites directly from CodePlex or GitHub.com repositories. Once connections are established between these services and your web sites, Windows Azure will automatically be notified every time a check-in occurs. This will then trigger Windows Azure to pull the source and compile/deploy the new version of your app to your web site automatically. Walk-through videos on how to perform these functions are below: Publishing to an Azure Web Site from CodePlex Publishing to an Azure Web Site from GitHub.com These changes, as well as the enhancements to the reserved plan model, make Windows Azure Web Sites a truly competitive hosting option. It’s never been easier or cheaper for a web developer to get up and running. Check out the free Windows Azure web site offering and see for yourself. Stay tuned to my twitter feed for Windows Azure announcements, updates, and links: @clinted

  Read the article

• Can't remove the libpcap0.8 package

  - by Yogesh

  I am getting error when running apt-get remove root@System:~/Downloads# sudo apt-get remove The following packages have unmet dependencies: libpcap0.8 : Breaks: libpcap0.8:i386 (!= 1.4.0-2) but 1.5.3-2 is installed libpcap0.8:i386 : Breaks: libpcap0.8 (!= 1.5.3-2) but 1.4.0-2 is installed libpcap0.8-dev : Depends: libpcap0.8 (= 1.5.3-2) but 1.4.0-2 is installed E: Unmet dependencies. Try using -f. and when I ran apt-get remove -f this is what happens: root@System:~/Downloads# sudo apt-get remove -f The following extra packages will be installed: libpcap0.8 The following packages will be upgraded: libpcap0.8 1 upgraded, 0 newly installed, 0 to remove and 365 not upgraded. 2 not fully installed or removed. Need to get 0 B/110 kB of archives. After this operation, 13.3 kB of additional disk space will be used. Do you want to continue? [Y/n] y (Reading database ... 163539 files and directories currently installed.) Preparing to unpack .../libpcap0.8_1.5.3-2_amd64.deb ... Unpacking libpcap0.8:amd64 (1.5.3-2) over (1.4.0-2) ... dpkg: error processing archive /var/cache/apt/archives/libpcap0.8_1.5.3-2_amd64.deb (--unpack): trying to overwrite shared '/usr/share/man/man7/pcap-filter.7.gz', which is different from other instances of package libpcap0.8:amd64 dpkg-deb: error: subprocess paste was killed by signal (Broken pipe) Processing triggers for man-db (2.6.7.1-1) ... Errors were encountered while processing: /var/cache/apt/archives/libpcap0.8_1.5.3-2_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1) root@System:~/Downloads# clear root@System:~/Downloads# sudo apt-get remove -f Reading package lists... Done Building dependency tree Reading state information... Done Correcting dependencies... Done The following extra packages will be installed: libpcap0.8 The following packages will be upgraded: libpcap0.8 1 upgraded, 0 newly installed, 0 to remove and 365 not upgraded. 2 not fully installed or removed. Need to get 0 B/110 kB of archives. After this operation, 13.3 kB of additional disk space will be used. Do you want to continue? [Y/n] y (Reading database ... 163539 files and directories currently installed.) Preparing to unpack .../libpcap0.8_1.5.3-2_amd64.deb ... Unpacking libpcap0.8:amd64 (1.5.3-2) over (1.4.0-2) ... dpkg: error processing archive /var/cache/apt/archives/libpcap0.8_1.5.3-2_amd64.deb (--unpack): trying to overwrite shared '/usr/share/man/man7/pcap-filter.7.gz', which is different from other instances of package libpcap0.8:amd64 dpkg-deb: error: subprocess paste was killed by signal (Broken pipe) Processing triggers for man-db (2.6.7.1-1) ... Errors were encountered while processing: /var/cache/apt/archives/libpcap0.8_1.5.3-2_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1) root@System:~/Downloads# root@System:~/Downloads# sudo apt-get check Reading package lists... Done Building dependency tree Reading state information... Done You might want to run 'apt-get -f install' to correct these. The following packages have unmet dependencies: libpcap0.8 : Breaks: libpcap0.8:i386 (!= 1.4.0-2) but 1.5.3-2 is installed libpcap0.8:i386 : Breaks: libpcap0.8 (!= 1.5.3-2) but 1.4.0-2 is installed libpcap0.8-dev : Depends: libpcap0.8 (= 1.5.3-2) but 1.4.0-2 is installed E: Unmet dependencies. Try using -f. root@System:~/Downloads# apt-cache policy libpcap0.8:amd64 libpcap0.8 libpcap0.8-dev libpcap0.8: Installed: 1.4.0-2 Candidate: 1.5.3-2 Version table: 1.5.3-2 0 500 http://in.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages *** 1.4.0-2 0 100 /var/lib/dpkg/status libpcap0.8: Installed: 1.4.0-2 Candidate: 1.5.3-2 Version table: 1.5.3-2 0 500 http://in.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages *** 1.4.0-2 0 100 /var/lib/dpkg/status libpcap0.8-dev: Installed: 1.5.3-2 Candidate: 1.5.3-2 Version table: *** 1.5.3-2 0 500 http://in.archive.ubuntu.com/ubuntu/ trusty/main amd64 Packages 100 /var/lib/dpkg/status root@System:~/Downloads# root@System:~/Downloads# sudo apt-get -f remove libpcap0.8 libpcap0.8-dev libpcap0.8-dev:i386 libpcap0.8:i386 Reading package lists... Done Building dependency tree Reading state information... Done Package 'libpcap0.8-dev:i386' is not installed, so not removed. Did you mean 'libpcap0.8-dev'? You might want to run 'apt-get -f install' to correct these: The following packages have unmet dependencies: libpcap-dev : Depends: libpcap0.8-dev but it is not going to be installed E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution). root@System:~/Downloads# sudo apt-get -f install Reading package lists... Done Building dependency tree Reading state information... Done Correcting dependencies... Done The following extra packages will be installed: libpcap0.8 The following packages will be upgraded: libpcap0.8 1 upgraded, 0 newly installed, 0 to remove and 365 not upgraded. 2 not fully installed or removed. Need to get 0 B/110 kB of archives. After this operation, 13.3 kB of additional disk space will be used. Do you want to continue? [Y/n] y (Reading database ... 163539 files and directories currently installed.) Preparing to unpack .../libpcap0.8_1.5.3-2_amd64.deb ... Unpacking libpcap0.8:amd64 (1.5.3-2) over (1.4.0-2) ... dpkg: error processing archive /var/cache/apt/archives/libpcap0.8_1.5.3-2_amd64.deb (--unpack): trying to overwrite shared '/usr/share/man/man7/pcap-filter.7.gz', which is different from other instances of package libpcap0.8:amd64 dpkg-deb: error: subprocess paste was killed by signal (Broken pipe) Processing triggers for man-db (2.6.7.1-1) ... Errors were encountered while processing: /var/cache/apt/archives/libpcap0.8_1.5.3-2_amd64.deb E: Sub-process /usr/bin/dpkg returned an error code (1) root@System:~/Downloads#

  Read the article

• Upgrading Agent Controllers in Oracle Enterprise Manager Ops Center 12c

  - by S Stelting

  Oracle Enterprise Manager Ops Center 12c recently released an upgrade for Solaris Agent Controllers. In this week's blog post, we'll show you how to upgrade agent controllers. Detailed instructions about upgrading Agent Controllers are available in the product documentation here. This blog post uses an Enterprise Controller which is configured for connected mode operation. If you'd like to apply the agent update in a disconnected installation, additional instructions are available here. Step 1: Download Agent Controller Updates With a connected mode Ops Center installation, you can check for product updates at any time by selecting the Enterprise Controller from the left-hand Administration navigation tab. Select the right-hand Action link “Ops Center Downloads” to open a pop-up dialog displaying any new product updates. In this example, the Enterprise Controller has already been upgraded to the latest version (Update 1, also shown as build version 2076) so only the Agent Controller updates will appear. There are three updates available: one for Solaris 10 X86, one for Solaris 8-10 SPARC, and one for all versions of Solaris 11. Note that the last update in the screen shot is the Solaris 11 update; for details on any of the downloads, place your mouse over the information icon under the details column for a pop-up text region. Select the software to download and click the Next button to display the Ops Center license agreement. Review and click the check box to accept the license agreement, then click the Next button to begin downloading the software. The status screen shows the current download status. If desired, you can perform the downloads as a background job. Simply click the check box, then click the next button to proceed to the summary screen. The summary screen shows the updates to be downloaded as well as the current status. Clicking the Finish button will close the dialog and return to the Browser UI. The download job will continue to run in Ops Center and progress can still be viewed from the jobs menu at the bottom of the browser window. Step 2: Check the Version of Existing Agent Controllers After the download job completes, you can check the availability of agent updates as well as the current versions of your Agent Controllers from the left-hand Assets navigation tab. Select “Operating Systems” from the pull-down tab lets to display only OS assets. Next, select “Solaris” in the left-hand tab to display the Solaris assets. Finally, select the Summary tab in the center display panel to show which versions of agent controllers are installed in your data center. Notice that a few of the OS assets are not displayed in the Agent Controllers tab. Ops Center will not display OS instances which do not have an Agent Controller installation. This includes Enterprise Controllers and Proxy Controllers (unless the agent has been activated on the OS instance) and and OS instances using agentless management. For Agent Controllers which support an update, the version of agent software (in this example, 2083) appears to the right of the currently installed version. Step 3: Upgrade Your Agent Controllers If desired, you can upgrade agent controllers from the previous screen by selecting the desired systems and clicking the upgrade button. Alternatively, you can click the link “Upgrade All Agent Controllers” in the right-hand Actions menu: In either case, a pop-up dialog lets you start the upgrade process. The first screen in the dialog lets you choose the upgrade method: Ops Center provides three ways to upgrade agent controllers: Automatic Upgrade: If Agent Controllers are running on all assets, Ops Center can automatically upgrade the software to the latest version without requiring any login credentials to the system SSH using a single set of credentials: If all assets use the same login credentials, you can apply a single set to all assets for the upgrade process. The log-in credentials are the same ones used for asset discovery and management, which are stored in the Plan Management navigation tab under Credentials. SSH using individual credentials: If assets use different login credentials, you can select a different set for each asset. After selecting the upgrade method, click the Next button to proceed to the summary screen. Click the Finish button to close the pop-up dialog and start the upgrade job for the agent controllers. The upgrade job runs a series of tasks in parallel, and will upgrade all agents which have been selected. Once the job completes, the OS instances in your data center will be upgraded and running the latest version of Agent Controller software.

  Read the article

• Rebuilding CoasterBuzz, Part II: Hot data objects

  - by Jeff

  This is the second post, originally from my personal blog, in a series about rebuilding one of my Web sites, which has been around for 12 years. More: Part I: Evolution, and death to WCF After the rush to get moving on stuff, I temporarily lost interest. I went almost two weeks without touching the project, in part because the next thing on my backlog was doing up a bunch of administrative pages. So boring. Unfortunately, because most of the site's content is user-generated, you need some facilities for editing data. CoasterBuzz has a database full of amusement parks and roller coasters. The entities enjoy the relationships that you would expect, though they're further defined by "instances" of a coaster, to define one that has moved between parks as one, with different names and operational dates. And of course, there are pictures and news items, too. It's not horribly complex, except when you have to account for a name change and display just the newest name. In all previous versions, data access was straight SQL. As so much of the old code was rooted in 2003, with some changes in 2008, there wasn't much in the way of ORM frameworks going on then. Let me rephrase that, I mostly wasn't interested in ORM's. Since that time, I used a little LINQ to SQL in some projects, and a whole bunch of nHibernate while at Microsoft. Through all of that experience, I have to admit that these frameworks are often a bigger pain in the ass than not. They're great for basic crud operations, but when you start having all kinds of exotic relationships, they get difficult, and generate all kinds of weird SQL under the covers. The black box can quickly turn into a black hole. Sometimes you end up having to build all kinds of new expertise to do things "right" with a framework. Still, despite my reservations, I used the newer version of Entity Framework, with the "code first" modeling, in a science project and I really liked it. Since it's just a right-click away with NuGet, I figured I'd give it a shot here. My initial effort was spent defining the context class, which requires a bit of work because I deviate quite a bit from the conventions that EF uses, starting with table names. Then throw some partial querying of certain tables (where you'll find image data), and you're splitting tables across several objects (navigation properties). I won't go into the details, because these are all things that are well documented around the Internet, but there was a minor learning curve there. The basics of reading data using EF are fantastic. For example, a roller coaster object has a park associated with it, as well as a number of instances (if it was ever relocated), and there also might be a big banner image for it. This is stupid easy to use because it takes one line of code in your repository class, and by the time you pass it to the view, you have a rich object graph that has everything you need to display stuff. Likewise, editing simple data is also, well, simple. For this goodness, thank the ASP.NET MVC framework. The UpdateModel() method on the controllers is very elegant. Remember the old days of assigning all kinds of properties to objects in your Webforms code-behind? What a time consuming mess that used to be. Even if you're not using an ORM tool, having hydrated objects come off the wire is such a time saver. Not everything is easy, though. When you have to persist a complex graph of objects, particularly if they were composed in the user interface with all kinds of AJAX elements and list boxes, it's not just a simple matter of submitting the form. There were a few instances where I ended up going back to "old-fashioned" SQL just in the interest of time. It's not that I couldn't do what I needed with EF, it's just that the efficiency, both my own and that of the generated SQL, wasn't good. Since EF context objects expose a database connection object, you can use that to do the old school ADO.NET stuff you've done for a decade. Using various extension methods from POP Forums' data project, it was a breeze. You just have to stick to your decision, in this case. When you start messing with SQL directly, you can't go back in the same code to messing with entities because EF doesn't know what you're changing. Not really a big deal. There are a number of take-aways from using EF. The first is that you write a lot less code, which has always been a desired outcome of ORM's. The other lesson, and I particularly learned this the hard way working on the MSDN forums back in the day, is that trying to retrofit an ORM framework into an existing schema isn't fun at all. The CoasterBuzz database isn't bad, but there are design decisions I'd make differently if I were starting from scratch. Now that I have some of this stuff done, I feel like I can start to move on to the more interesting things on the backlog. There's a lot to do, but at least it's fun stuff, and not more forms that will be used infrequently.

  Read the article

• Business Case for investing time developing Stubs and BizUnit Tests

  - by charlie.mott

  I was recently in a position where I had to justify why effort should be spent developing Stubbed Integration Tests for BizTalk solutions. These tests are usually developed using the BizUnit framework. I assumed that most seasoned BizTalk developers would consider this best practice. Even though Microsoft suggest use of BizUnit on MSDN, I've not found a single site listing the justifications for investing time writing stubs and BizUnit tests. Stubs Stubs should be developed to isolate your development team from external dependencies. This is described by Michael Stephenson here. Failing to do this can result in the following problems: In contract-first scenarios, the external system interface will have been defined.  But the interface may not have been setup or even developed yet for the BizTalk developers to work with. By the time you open the target location to see the data BizTalk has sent, it may have been swept away. If you are relying on the UI of the target system to see the data BizTalk has sent, what do you do if it fails to arrive? It may take time for the data to be processed or it may be scheduled to be processed later. Learning how to use the source\target systems and investigations into where things go wrong in these systems will slow down the BizTalk development effort. By the time the data is visible in a UI it may have undergone further transformations. In larger development teams working together, do you all use the same source and target instances. How do you know which data was created by whose tests? How do you know which event log error message are whose?  Another developer may have “cleaned up” your data. It is harder to write BizUnit tests that clean up the data\logs after each test run. What if your B2B partners' source or target system cannot support the sort of testing you want to do. They may not even have a development or test instance that you can work with. Their single test instance may be used by the SIT\UAT teams. There may be licencing costs of setting up an instances of the external system. The stubs I like to use are generic stubs that can accept\return any message type.  Usually I need to create one per protocol. They should be driven by BizUnit steps to: validates the data received; and select a response messages (or error response). Once built, they can be re-used for many integration tests and from project to project. I’m not saying that developers should never test against a real instance.  Every so often, you still need to connect to real developer or test instances of the source and target endpoints\services. The interface developers may ask you to send them some data to see if everything still works.  Or you might want some messages sent to BizTalk to get confidence that everything still works beyond BizTalk. Tests Automated “Stubbed Integration Tests” are usually built using the BizUnit framework. These facilitate testing of the entire integration process from source stub to target stub. It will ensure that all of the BizTalk components are configured together correctly to meet all the requirements. More fine grained unit testing of individual BizTalk components is still encouraged.  But BizUnit provides much the easiest way to test some components types (e.g. Orchestrations). Using BizUnit with the Behaviour Driven Development approach described by Mike Stephenson delivers the following benefits: source: http://biztalkbddsample.codeplex.com – Video 1. Requirements can be easily defined using Given/When/Then Requirements are close to the code so easier to manage as features and scenarios Requirements are defined in domain language The feature files can be used as part of the documentation The documentation is accurate to the build of code and can be published with a release The scenarios are effective to document the scenarios and are not over excessive The scenarios are maintained with the code There’s an abstraction between the intention and implementation of tests making them easier to understand The requirements drive the testing These same tests can also be used to drive load testing as described here. If you don't do this ... If you don't follow the above “Stubbed Integration Tests” approach, the developer will need to manually trigger the tests. This has the following risks: Developers are unlikely to check all the scenarios each time and all the expected conditions each time. After the developer leaves, these manual test steps may be lost. What test scenarios are there?  What test messages did they use for each scenario? There is no mechanism to prove adequate test coverage. A test team may attempt to automate integration test scenarios in a test environment through the triggering of tests from a source system UI. If this is a replacement for BizUnit tests, then this carries the following risks: It moves the tests downstream, so problems will be found later in the process. Testers may not check all the expected conditions within the BizTalk infrastructure such as: event logs, suspended messages, etc. These automated tests may also get in the way of manual tests run on these environments.

  Read the article

< Previous Page | 47 48 49 50 51 52 53 54 55 56 57 58  | Next Page >