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• Installing .NET 3.5 SP1 on server broke WCF

  - by Doron

  I installed .NET 3.5 SP1 on server which previously had .NET 3.0 SP2. Before install site was working perfectly. After install and subsequeny server restart, site displays but anything that makes use of the WCF service has stopped working. The exception log reports exceptions like the following when any calls are made to the client proxy: The communication object, System.ServiceModel.Channels.ServiceChannel, cannot be used for communication because it is in the Faulted state. The server's application event log gave the following errors after the install: Configuration section system.serviceModel.activation already exists in c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Config\machine.config. Configuration section system.runtime.serialization already exists in c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Config\machine.config. Configuration section system.serviceModel already exists in c:\WINDOWS\Microsoft.NET\Framework\v2.0.50727\Config\machine.config. which seems to be inline with the fact that anything WCF related has stopped working. I am not experienced in server configurations or WCF so looking for any assistance with this. Thanks!! From machine.config: <sectionGroup name="system.serviceModel" type="System.ServiceModel.Configuration.ServiceModelSectionGroup, System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <section name="behaviors" type="System.ServiceModel.Configuration.BehaviorsSection, System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/> <section name="bindings" type="System.ServiceModel.Configuration.BindingsSection, System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/> <section name="client" type="System.ServiceModel.Configuration.ClientSection, System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/> <section name="comContracts" type="System.ServiceModel.Configuration.ComContractsSection, System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/> <section name="commonBehaviors" type="System.ServiceModel.Configuration.CommonBehaviorsSection, System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" allowDefinition="MachineOnly" allowExeDefinition="MachineOnly"/> <section name="diagnostics" type="System.ServiceModel.Configuration.DiagnosticSection, System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/> <section name="extensions" type="System.ServiceModel.Configuration.ExtensionsSection, System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/> <section name="machineSettings" type="System.ServiceModel.Configuration.MachineSettingsSection, SMDiagnostics, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" allowDefinition="MachineOnly" allowExeDefinition="MachineOnly"/> <section name="serviceHostingEnvironment" type="System.ServiceModel.Configuration.ServiceHostingEnvironmentSection, System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/> <section name="services" type="System.ServiceModel.Configuration.ServicesSection, System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/> </sectionGroup> <sectionGroup name="system.serviceModel.activation" type="System.ServiceModel.Activation.Configuration.ServiceModelActivationSectionGroup, System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <section name="diagnostics" type="System.ServiceModel.Activation.Configuration.DiagnosticSection, System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/> <section name="net.pipe" type="System.ServiceModel.Activation.Configuration.NetPipeSection, System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/> <section name="net.tcp" type="System.ServiceModel.Activation.Configuration.NetTcpSection, System.ServiceModel, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/> </sectionGroup> <sectionGroup name="system.runtime.serialization" type="System.Runtime.Serialization.Configuration.SerializationSectionGroup, System.Runtime.Serialization, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"> <section name="dataContractSerializer" type="System.Runtime.Serialization.Configuration.DataContractSerializerSection, System.Runtime.Serialization, Version=3.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089"/> </sectionGroup> from site's web.config <sectionGroup name="system.web.extensions" type="System.Web.Configuration.SystemWebExtensionsSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"> <sectionGroup name="scripting" type="System.Web.Configuration.ScriptingSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"> <section name="scriptResourceHandler" type="System.Web.Configuration.ScriptingScriptResourceHandlerSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication" /> <sectionGroup name="webServices" type="System.Web.Configuration.ScriptingWebServicesSectionGroup, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"> <section name="jsonSerialization" type="System.Web.Configuration.ScriptingJsonSerializationSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="Everywhere" /> <section name="profileService" type="System.Web.Configuration.ScriptingProfileServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication" /> <section name="authenticationService" type="System.Web.Configuration.ScriptingAuthenticationServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication" /> <section name="roleService" type="System.Web.Configuration.ScriptingRoleServiceSection, System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35" requirePermission="false" allowDefinition="MachineToApplication" /> </sectionGroup> </sectionGroup> </sectionGroup> . . . <system.serviceModel> <bindings> <wsHttpBinding> <binding name="WSHttpBinding_IService" closeTimeout="00:03:00" openTimeout="00:03:00" receiveTimeout="00:10:00" sendTimeout="00:03:00" bypassProxyOnLocal="false" transactionFlow="false" hostNameComparisonMode="StrongWildcard" maxBufferPoolSize="524288" maxReceivedMessageSize="131072" messageEncoding="Text" textEncoding="utf-8" useDefaultWebProxy="true" allowCookies="false"> <readerQuotas maxDepth="32" maxStringContentLength="8192" maxArrayLength="16384" maxBytesPerRead="4096" maxNameTableCharCount="16384" /> <reliableSession ordered="true" inactivityTimeout="00:10:00" enabled="false" /> <security mode="Message"> <transport clientCredentialType="Windows" proxyCredentialType="None" realm="" /> <message clientCredentialType="Windows" negotiateServiceCredential="true" algorithmSuite="Default" establishSecurityContext="true" /> </security> </binding> </wsHttpBinding> </bindings> <client> <endpoint address="some address" binding="wsHttpBinding" bindingConfiguration="WSHttpBinding_IService" contract="some contact" name="WSHttpBinding_IService" /> </client> Pertinant Exception Section: Exception information: Exception type: TypeLoadException Exception message: Could not load type 'System.Web.UI.ScriptReferenceBase' from assembly 'System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31bf3856ad364e35'.

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• how to limit network bandwidth for testing (win7, virtualbox)

  - by bao

  Hi! I develop ASP.NET application on Windows 7 machine (IIS 7.5). I need to limit network bandwidth to test my AJAX GUI. What kind of software could you recommend for those cases: a) I deploy my app to the remote IIS box and try to limit bandwidth of my network connection in Windows 7. b) I deploy my app to the IIS installed on Win7 and try to test my app from Virtualbox machine via virtual network. So, any opinions?

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• build error, warning MSB3258

  - by Steed

  I have recently moved my solution from my main dev machine using vs2010 pro sp1 to a new machine. The setup is supposed to be the same except its failing to build. Its giving errors like c:\Windows\Microsoft.NET\Framework\v4.0.30319\Microsoft.Common.targets(1360,9): warning MSB3258: The primary reference "C:\rep\hms\trunk\ikassystemv3\ikasDAL\bin\Debug\ikasDAL.dll" could not be resolved because it has an indirect dependency on the .NET Framework assembly "mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" which has a higher version "4.0.0.0" than the version "2.0.0.0" in the current target framework. However all all the libraries in question are set to use the .net 2 framework and I need it this way or else it will break stuff that uses them. However for some reason it seems to think that somehow my .net 2 system libs are somehow referencing .net 4 stuff. All the referenced libs are .net 2 You can see my build output here http://tinyurl.com/bnugru4

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• Mobile Device emulator cannot access localhost

  - by Diana

  I am using Windows Mobile 6 Professional Emulator and Windows Mobile Device Center. I connected and cradled the emulator to my computer. I am trying to connect from the browser of the emulator to a webservice that is deployed in the IIS of my computer (same machine where the emulator is installed). If I connect my computer to the internet, I can access any website, including my local WS (using the IP returned by ipConfig). The problem is when I disconnect the computer from the Internet: I cannot access my local web service using the IP (internal one returned by ipconfig), or machine name. Do you have any ideea what settings am I missing? I am sure this it's possible somehow, I just don't know how... PS: The goal is to access the WS from a mobile application, but until I cannot access it from the browser, I cannot access it from the application either. Thank you!

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• RPC Runtime exception

  - by viswanathan

  Hi I am having an application which requires inter process communication between different processes in different machines. Assume i have 2 processes in different machines which communicate usnig RPC. Everything works fine in the normal case. Now if i remove network and reconnect the same my processes still work however what happens is sometimes an RPC call(which sends a message from one process on one machine to another process on another machine) fails with an error code value of 3765269347, which may not really make any sense. This failure occurs only sometimes and i have no clue as to why this occurs. Anybody knows any reason why this may occur or general network related RPC issues. Thanks in advance.

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• Strange error occurring when using wcf to run query against sql server

  - by vondip

  Hi all, I am building an asp.net application, using II6 on windows server 2003 (vps hosting). I am confronted with an error I didn't receive on my development machine (windows 7, iis 7.5, 64 bit). When my wcf service tries launching my query running against a local sql server this is the error I receive: Memory gates checking failed because the free memory (43732992 bytes) is less than 5% of total memory. As a result, the service will not be available for incoming requests. To resolve this, either reduce the load on the machine or adjust the value of minFreeMemoryPercentageToActivateService on the serviceHostingEnvironment config element. and ideas??

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• RadComboBox Just Freezes

  - by ProfK

  I have two examples now, my first two, where a place a RadComboBox on a web form, and populate it, but it won't drop down. I first picked this up on a big web application project, and then on a simple little web site project, for investigating this. In my sample project, it is the only control on the page besides the ScriptManager, and there are rows in the data source, and it does display the first row, but it just doesn't drop down. Any ideas on this? BTW, this is theh first time I've restored this project onto a new XP machine, where I previously was working on a Vista machine that died.

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• DirectX application doesn't work over Remote Desktop

  - by emddudley

  I have a WPF application which has a DirectX component within it. This component does not work over Remote Desktop--it just shows a corrupted image. The application works fine when not using Remote Desktop. In trying to debug the problem I installed the February 2010 DirectX SDK. Now, when I run the program on the computer with the SDK and Remote Desktop to it from a separate computer, the component works just fine. However the opposite does not work--trying to use the application over Remote Desktop when it is running on the computer without the DirectX SDK (it has the original problem with the corrupted image). I have already compared the loaded DLLs (using Process Explorer) between running the application on my SDK machine and non-SDK machine. They both are loading the same DLL versions. What else could be causing this behavior?

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• SQL SERVER – Concurrency Basics – Guest Post by Vinod Kumar

  - by pinaldave

  This guest post is by Vinod Kumar. Vinod Kumar has worked with SQL Server extensively since joining the industry over a decade ago. Working on various versions from SQL Server 7.0, Oracle 7.3 and other database technologies – he now works with the Microsoft Technology Center (MTC) as a Technology Architect. Let us read the blog post in Vinod’s own voice. Learning is always fun when it comes to SQL Server and learning the basics again can be more fun. I did write about Transaction Logs and recovery over my blogs and the concept of simplifying the basics is a challenge. In the real world we always see checks and queues for a process – say railway reservation, banks, customer supports etc there is a process of line and queue to facilitate everyone. Shorter the queue higher is the efficiency of system (a.k.a higher is the concurrency). Every database does implement this using checks like locking, blocking mechanisms and they implement the standards in a way to facilitate higher concurrency. In this post, let us talk about the topic of Concurrency and what are the various aspects that one needs to know about concurrency inside SQL Server. Let us learn the concepts as one-liners: Concurrency can be defined as the ability of multiple processes to access or change shared data at the same time. The greater the number of concurrent user processes that can be active without interfering with each other, the greater the concurrency of the database system. Concurrency is reduced when a process that is changing data prevents other processes from reading that data or when a process that is reading data prevents other processes from changing that data. Concurrency is also affected when multiple processes are attempting to change the same data simultaneously. Two approaches to managing concurrent data access: Optimistic Concurrency Model Pessimistic Concurrency Model Concurrency Models Pessimistic Concurrency Default behavior: acquire locks to block access to data that another process is using. Assumes that enough data modification operations are in the system that any given read operation is likely affected by a data modification made by another user (assumes conflicts will occur). Avoids conflicts by acquiring a lock on data being read so no other processes can modify that data. Also acquires locks on data being modified so no other processes can access the data for either reading or modifying. Readers block writer, writers block readers and writers. Optimistic Concurrency Assumes that there are sufficiently few conflicting data modification operations in the system that any single transaction is unlikely to modify data that another transaction is modifying. Default behavior of optimistic concurrency is to use row versioning to allow data readers to see the state of the data before the modification occurs. Older versions of the data are saved so a process reading data can see the data as it was when the process started reading and not affected by any changes being made to that data. Processes modifying the data is unaffected by processes reading the data because the reader is accessing a saved version of the data rows. Readers do not block writers and writers do not block readers, but, writers can and will block writers. Transaction Processing A transaction is the basic unit of work in SQL Server. Transaction consists of SQL commands that read and update the database but the update is not considered final until a COMMIT command is issued (at least for an explicit transaction: marked with a BEGIN TRAN and the end is marked by a COMMIT TRAN or ROLLBACK TRAN). Transactions must exhibit all the ACID properties of a transaction. ACID Properties Transaction processing must guarantee the consistency and recoverability of SQL Server databases. Ensures all transactions are performed as a single unit of work regardless of hardware or system failure. A – Atomicity C – Consistency I – Isolation D- Durability Atomicity: Each transaction is treated as all or nothing – it either commits or aborts. Consistency: ensures that a transaction won’t allow the system to arrive at an incorrect logical state – the data must always be logically correct.  Consistency is honored even in the event of a system failure. Isolation: separates concurrent transactions from the updates of other incomplete transactions. SQL Server accomplishes isolation among transactions by locking data or creating row versions. Durability: After a transaction commits, the durability property ensures that the effects of the transaction persist even if a system failure occurs. If a system failure occurs while a transaction is in progress, the transaction is completely undone, leaving no partial effects on data. Transaction Dependencies In addition to supporting all four ACID properties, a transaction might exhibit few other behaviors (known as dependency problems or consistency problems). Lost Updates: Occur when two processes read the same data and both manipulate the data, changing its value and then both try to update the original data to the new value. The second process might overwrite the first update completely. Dirty Reads: Occurs when a process reads uncommitted data. If one process has changed data but not yet committed the change, another process reading the data will read it in an inconsistent state. Non-repeatable Reads: A read is non-repeatable if a process might get different values when reading the same data in two reads within the same transaction. This can happen when another process changes the data in between the reads that the first process is doing. Phantoms: Occurs when membership in a set changes. It occurs if two SELECT operations using the same predicate in the same transaction return a different number of rows. Isolation Levels SQL Server supports 5 isolation levels that control the behavior of read operations. Read Uncommitted All behaviors except for lost updates are possible. Implemented by allowing the read operations to not take any locks, and because of this, it won’t be blocked by conflicting locks acquired by other processes. The process can read data that another process has modified but not yet committed. When using the read uncommitted isolation level and scanning an entire table, SQL Server can decide to do an allocation order scan (in page-number order) instead of a logical order scan (following page pointers). If another process doing concurrent operations changes data and move rows to a new location in the table, the allocation order scan can end up reading the same row twice. Also can happen if you have read a row before it is updated and then an update moves the row to a higher page number than your scan encounters later. Performing an allocation order scan under Read Uncommitted can cause you to miss a row completely – can happen when a row on a high page number that hasn’t been read yet is updated and moved to a lower page number that has already been read. Read Committed Two varieties of read committed isolation: optimistic and pessimistic (default). Ensures that a read never reads data that another application hasn’t committed. If another transaction is updating data and has exclusive locks on data, your transaction will have to wait for the locks to be released. Your transaction must put share locks on data that are visited, which means that data might be unavailable for others to use. A share lock doesn’t prevent others from reading but prevents them from updating. Read committed (snapshot) ensures that an operation never reads uncommitted data, but not by forcing other processes to wait. SQL Server generates a version of the changed row with its previous committed values. Data being changed is still locked but other processes can see the previous versions of the data as it was before the update operation began. Repeatable Read This is a Pessimistic isolation level. Ensures that if a transaction revisits data or a query is reissued the data doesn’t change. That is, issuing the same query twice within a transaction cannot pickup any changes to data values made by another user’s transaction because no changes can be made by other transactions. However, this does allow phantom rows to appear. Preventing non-repeatable read is a desirable safeguard but cost is that all shared locks in a transaction must be held until the completion of the transaction. Snapshot Snapshot Isolation (SI) is an optimistic isolation level. Allows for processes to read older versions of committed data if the current version is locked. Difference between snapshot and read committed has to do with how old the older versions have to be. It’s possible to have two transactions executing simultaneously that give us a result that is not possible in any serial execution. Serializable This is the strongest of the pessimistic isolation level. Adds to repeatable read isolation level by ensuring that if a query is reissued rows were not added in the interim, i.e, phantoms do not appear. Preventing phantoms is another desirable safeguard, but cost of this extra safeguard is similar to that of repeatable read – all shared locks in a transaction must be held until the transaction completes. In addition serializable isolation level requires that you lock data that has been read but also data that doesn’t exist. Ex: if a SELECT returned no rows, you want it to return no. rows when the query is reissued. This is implemented in SQL Server by a special kind of lock called the key-range lock. Key-range locks require that there be an index on the column that defines the range of values. If there is no index on the column, serializable isolation requires a table lock. Gets its name from the fact that running multiple serializable transactions at the same time is equivalent of running them one at a time. Now that we understand the basics of what concurrency is, the subsequent blog posts will try to bring out the basics around locking, blocking, deadlocks because they are the fundamental blocks that make concurrency possible. Now if you are with me – let us continue learning for SQL Server Locking Basics. Reference: Pinal Dave (http://blog.sqlauthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Performance, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: Concurrency

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• AccountManagement.UserPrincipal.Current takes 5 seconds

  - by Adel Hazzah

  I'm using the new .NET 3.5 System.DirectoryServices.AccountManagement API. In my code, I need to determine the current System.DirectoryServices.AccountManagement.UserPrincipal. My naive approach was to do this: using AccountManagement = System.DirectoryServices.AccountManagement; ... // Determine current UserPrincipal. // (On my machine, this blocks for 5 seconds) // AccountManagement.UserPrincipal principal = AccountManagement.UserPrincipal.Current; My computer is a stand-alone machine running Vista. I am not part of any domain, etc. Any ideas on how to improve the performance?

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• socat usage for FIFO speed vs socket speed on localhost

  - by Fishy

  Hello, As per a suggestion on stackoverflow, to compare IPC on a single machine using a) sockets (TCP) on localhost to localhost b) using FIFOs (between Java and C) To answer (a), I used netcat to gauge transfer speed (91 MBytes/sec)[1] (b) Q: How can I test FIFO write speed using socat? My approach(where /tmp/gus is created using mkfifo on RHEL): dd if=/dev/zero of=/tmp/gus bs=1G count=1 but i get: 1073741824 bytes (1.1 GB) copied, 1.1326 seconds, 948 MB/s Does this mean writing to a FIFO ~10 times faster? Or is my experiment completely wrong ? Thank you Sporsi [1] From machine A to B across 1Gbps link, this number dropped to ~80 MBytes/sec - I expected localhost to be much higher ...

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• Connect to a wireless network programmatically

  - by Josh Adams

  I'm trying to write an application that connects to my company's wireless network automatically on windows XP. I've found the Wireless LAN API but it requires me to have some hotfix installed on the machine, and you need to have sp2 or higher(There are machines with SP1, and I'm required to support any XP machine). I've tried to find some samples about Wireless Zero Configuration on MSDN but with no luck, only samples I've found are for WinCE, I think Microsoft stopped supporting it. In addition I couldn't find where to download the dll and header file for working with the WZC. There must be a way to do it and work on any service pack because I've found Zwlancfg by ENGL

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• Selenium RC > how to upload file using attachFile()

  - by Saara

  hello, I am using Selenium RC with Junit framework. I am trying to upload a file using attachFile() method. attachFile: (Information collected from selenium API http://release.seleniumhq.org/selenium-remote-control/1.0-beta-2/doc/java/com/thoughtworks/selenium/Selenium.html#attachFile(java.lang.String,%20java.lang.String)) void attachFile(java.lang.String fieldLocator, java.lang.String fileLocator) Sets a file input (upload) field to the file listed in fileLocator Parameters: fieldLocator - an element locator fileLocator - a URL pointing to the specified file. Before the file can be set in the input field (fieldLocator), Selenium RC may need to transfer the file to the local machine before attaching the file in a web page form. This is common in selenium grid configurations where the RC server driving the browser is not the same machine that started the test. Supported Browsers: Firefox ("*chrome") only. Can anyone please tell me how to define "fileLocator". I am not getting which URL to be specify over here. Please give me an example if possible.

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• Some unit tests fail in automated Team Build task

  - by weenet

  I have an odd situation. I have a suite of unit tests that pass on my dev machine. They pass on the build machine if run from visual studio. But 5 of them reliably fail during the automated build. There is nothing noteworthy about the ones that fail that I can see (and I've stared at them a long time). Anyone seen anything like this? Is there a way to see the test output in the Team Build log? All I get is Passed or Failed messages, but not the Assert message. Thanks!

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• Announcing ASP.NET MVC 3 (Release Candidate 2)

  - by ScottGu

  Earlier today the ASP.NET team shipped the final release candidate (RC2) for ASP.NET MVC 3.  You can download and install it here. Almost there… Today’s RC2 release is the near-final release of ASP.NET MVC 3, and is a true “release candidate” in that we are hoping to not make any more code changes with it.  We are publishing it today so that people can do final testing with it, let us know if they find any last minute “showstoppers”, and start updating their apps to use it.  We will officially ship the final ASP.NET MVC 3 “RTM” build in January. Works with both VS 2010 and VS 2010 SP1 Beta Today’s ASP.NET MVC 3 RC2 release works with both the shipping version of Visual Studio 2010 / Visual Web Developer 2010 Express, as well as the newly released VS 2010 SP1 Beta.  This means that you do not need to install VS 2010 SP1 (or the SP1 beta) in order to use ASP.NET MVC 3.  It works just fine with the shipping Visual Studio 2010.  I’ll do a blog post next week, though, about some of the nice additional feature goodies that come with VS 2010 SP1 (including IIS Express and SQL CE support within VS) which make the dev experience for both ASP.NET Web Forms and ASP.NET MVC even better. Bugs and Perf Fixes Today’s ASP.NET MVC 3 RC2 build contains many bug fixes and performance optimizations.  Our latest performance tests indicate that ASP.NET MVC 3 is now faster than ASP.NET MVC 2, and that existing ASP.NET MVC applications will experience a slight performance increase when updated to run using ASP.NET MVC 3. Final Tweaks and Fit-N-Finish In addition to bug fixes and performance optimizations, today’s RC2 build contains a number of last-minute feature tweaks and “fit-n-finish” changes for the new ASP.NET MVC 3 features.  The feedback and suggestions we’ve received during the public previews has been invaluable in guiding these final tweaks, and we really appreciate people’s support in sending this feedback our way.  Below is a short-list of some of the feature changes/tweaks made between last month’s ASP.NET MVC 3 RC release and today’s ASP.NET MVC 3 RC2 release: jQuery updates and addition of jQuery UI The default ASP.NET MVC 3 project templates have been updated to include jQuery 1.4.4 and jQuery Validation 1.7.  We are also excited to announce today that we are including jQuery UI within our default ASP.NET project templates going forward.  jQuery UI provides a powerful set of additional UI widgets and capabilities.  It will be added by default to your project’s \scripts folder when you create new ASP.NET MVC 3 projects. Improved View Scaffolding The T4 templates used for scaffolding views with the Add-View dialog now generates views that use Html.EditorFor instead of helpers such as Html.TextBoxFor. This change enables you to optionally annotate models with metadata (using data annotation attributes) to better customize the output of your UI at runtime. The Add View scaffolding also supports improved detection and usage of primary key information on models (including support for naming conventions like ID, ProductID, etc).  For example: the Add View dialog box uses this information to ensure that the primary key value is not scaffold as an editable form field, and that links between views are auto-generated correctly with primary key information. The default Edit and Create templates also now include references to the jQuery scripts needed for client validation.  Scaffold form views now support client-side validation by default (no extra steps required).  Client-side validation with ASP.NET MVC 3 is also done using an unobtrusive javascript approach – making pages fast and clean. [ControllerSessionState] –> [SessionState] ASP.NET MVC 3 adds support for session-less controllers.  With the initial RC you used a [ControllerSessionState] attribute to specify this.  We shortened this in RC2 to just be [SessionState]: Note that in addition to turning off session state, you can also set it to be read-only (which is useful for webfarm scenarios where you are reading but not updating session state on a particular request). [SkipRequestValidation] –> [AllowHtml] ASP.NET MVC includes built-in support to protect against HTML and Cross-Site Script Injection Attacks, and will throw an error by default if someone tries to post HTML content as input.  Developers need to explicitly indicate that this is allowed (and that they’ve hopefully built their app to securely support it) in order to enable it. With ASP.NET MVC 3, we are also now supporting a new attribute that you can apply to properties of models/viewmodels to indicate that HTML input is enabled, which enables much more granular protection in a DRY way.  In last month’s RC release this attribute was named [SkipRequestValidation].  With RC2 we renamed it to [AllowHtml] to make it more intuitive: Setting the above [AllowHtml] attribute on a model/viewmodel will cause ASP.NET MVC 3 to turn off HTML injection protection when model binding just that property. Html.Raw() helper method The new Razor view engine introduced with ASP.NET MVC 3 automatically HTML encodes output by default.  This helps provide an additional level of protection against HTML and Script injection attacks. With RC2 we are adding a Html.Raw() helper method that you can use to explicitly indicate that you do not want to HTML encode your output, and instead want to render the content “as-is”: ViewModel/View –> ViewBag ASP.NET MVC has (since V1) supported a ViewData[] dictionary within Controllers and Views that enables developers to pass information from a Controller to a View in a late-bound way.  This approach can be used instead of, or in combination with, a strongly-typed model class.  The below code demonstrates a common use case – where a strongly typed Product model is passed to the view in addition to two late-bound variables via the ViewData[] dictionary: With ASP.NET MVC 3 we are introducing a new API that takes advantage of the dynamic type support within .NET 4 to set/retrieve these values.  It allows you to use standard “dot” notation to specify any number of additional variables to be passed, and does not require that you create a strongly-typed class to do so.  With earlier previews of ASP.NET MVC 3 we exposed this API using a dynamic property called “ViewModel” on the Controller base class, and with a dynamic property called “View” within view templates.  A lot of people found the fact that there were two different names confusing, and several also said that using the name ViewModel was confusing in this context – since often you create strongly-typed ViewModel classes in ASP.NET MVC, and they do not use this API.  With RC2 we are exposing a dynamic property that has the same name – ViewBag – within both Controllers and Views.  It is a dynamic collection that allows you to pass additional bits of data from your controller to your view template to help generate a response.  Below is an example of how we could use it to pass a time-stamp message as well as a list of all categories to our view template: Below is an example of how our view template (which is strongly-typed to expect a Product class as its model) can use the two extra bits of information we passed in our ViewBag to generate the response.  In particular, notice how we are using the list of categories passed in the dynamic ViewBag collection to generate a dropdownlist of friendly category names to help set the CategoryID property of our Product object.  The above Controller/View combination will then generate an HTML response like below.    Output Caching Improvements ASP.NET MVC 3’s output caching system no longer requires you to specify a VaryByParam property when declaring an [OutputCache] attribute on a Controller action method.  MVC3 now automatically varies the output cached entries when you have explicit parameters on your action method – allowing you to cleanly enable output caching on actions using code like below: In addition to supporting full page output caching, ASP.NET MVC 3 also supports partial-page caching – which allows you to cache a region of output and re-use it across multiple requests or controllers.  The [OutputCache] behavior for partial-page caching was updated with RC2 so that sub-content cached entries are varied based on input parameters as opposed to the URL structure of the top-level request – which makes caching scenarios both easier and more powerful than the behavior in the previous RC. @model declaration does not add whitespace In earlier previews, the strongly-typed @model declaration at the top of a Razor view added a blank line to the rendered HTML output. This has been fixed so that the declaration does not introduce whitespace. Changed "Html.ValidationMessage" Method to Display the First Useful Error Message The behavior of the Html.ValidationMessage() helper was updated to show the first useful error message instead of simply displaying the first error. During model binding, the ModelState dictionary can be populated from multiple sources with error messages about the property, including from the model itself (if it implements IValidatableObject), from validation attributes applied to the property, and from exceptions thrown while the property is being accessed. When the Html.ValidationMessage() method displays a validation message, it now skips model-state entries that include an exception, because these are generally not intended for the end user. Instead, the method looks for the first validation message that is not associated with an exception and displays that message. If no such message is found, it defaults to a generic error message that is associated with the first exception. RemoteAttribute “Fields” -> “AdditionalFields” ASP.NET MVC 3 includes built-in remote validation support with its validation infrastructure.  This means that the client-side validation script library used by ASP.NET MVC 3 can automatically call back to controllers you expose on the server to determine whether an input element is indeed valid as the user is editing the form (allowing you to provide real-time validation updates). You can accomplish this by decorating a model/viewmodel property with a [Remote] attribute that specifies the controller/action that should be invoked to remotely validate it.  With the RC this attribute had a “Fields” property that could be used to specify additional input elements that should be sent from the client to the server to help with the validation logic.  To improve the clarity of what this property does we have renamed it to “AdditionalFields” with today’s RC2 release. ViewResult.Model and ViewResult.ViewBag Properties The ViewResult class now exposes both a “Model” and “ViewBag” property off of it.  This makes it easier to unit test Controllers that return views, and avoids you having to access the Model via the ViewResult.ViewData.Model property. Installation Notes You can download and install the ASP.NET MVC 3 RC2 build here.  It can be installed on top of the previous ASP.NET MVC 3 RC release (it should just replace the bits as part of its setup). The one component that will not be updated by the above setup (if you already have it installed) is the NuGet Package Manager.  If you already have NuGet installed, please go to the Visual Studio Extensions Manager (via the Tools –> Extensions menu option) and click on the “Updates” tab.  You should see NuGet listed there – please click the “Update” button next to it to have VS update the extension to today’s release. If you do not have NuGet installed (and did not install the ASP.NET MVC RC build), then NuGet will be installed as part of your ASP.NET MVC 3 setup, and you do not need to take any additional steps to make it work. Summary We are really close to the final ASP.NET MVC 3 release, and will deliver the final “RTM” build of it next month.  It has been only a little over 7 months since ASP.NET MVC 2 shipped, and I’m pretty amazed by the huge number of new features, improvements, and refinements that the team has been able to add with this release (Razor, Unobtrusive JavaScript, NuGet, Dependency Injection, Output Caching, and a lot, lot more).  I’ll be doing a number of blog posts over the next few weeks talking about many of them in more depth. Hope this helps, Scott P.S. In addition to blogging, I am also now using Twitter for quick updates and to share links. Follow me at: twitter.com/scottgu

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• problem with codeigniter using odbc database driver

  - by Nir Gavish

  i’ve run into a curious problem with codeigniter's odbc driver. i’m connecting from a linux machine to an MSSQL 2008 machine using FreeTDS. while i get that the ‘num_rows’ function always returns -1, and that is fully a database/driver issue - for some reason when i try to create a -result(), the whole application crashes (error 500, sometimes just a blank page), if i’m lucky, i get an error message informing me that the application died because it tried to allocated 2 terrabytes of memory(!). This happens irregularly, ie: every few refreshes. sometimes it runs fine, sometimes the page returns error 500 and sometimes it gives the memory allocation error - in any case it’s not really something that can be reproduced with percision, and the queries are SUPER simple. ideas anyone?

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• Exception from HRESULT: 0x800A03EC

  - by Daniel

  Any help is appreciated: I'm developing a C#.Net app in VS2010 that interacts with Excel. The app works correctly on my local machine. Uploading to a remote Windows 2003 server however, breaks the app. Originally, I received the following message Retrieving the COM class factory for component with CLSID {00024500-0000-0000-C000-000000000046} failed due to the following error: 80070005 After Googling the problem (which suggested a permissions problem) i tried this: Installing Excel 2007 Going into Component Services on the remote server and following the instructions here: http://blog.crowe.co.nz/archive/2006/03/02/589.aspx Now I get this message on the same operation: Exception from HRESULT: 0x800A03EC Google searches seem to be suggesting that this is a version match error. However, both the local machine and the remote server use Excel 2007. Any suggestions would be very welcome. Thanks in advance. -Daniel

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• Visual C# 2008 Express connection to SQL Server 2008 Express problem

  - by Phil

  Hi guys, I have a problem with Visual C# 2008 express (SP1) connecting to SQL Server 2008 express. The "Add Connection" window (wherever initiated) doesn't list existing sql server and no option for sql server except a compact edition. Note that, I've got the VWD 2008 express (SP1) on the same machine which shows the window regularly (with SQL server listed) and SQL Server Management studio works fine with the server as well. I've seen other similar posts, did take some advices: reinstalled the VC#, services run ok, etc... but with no success with VC# so far. Again, on the same machine the VWD shows the dialog with sql server option regularly, but VC# shows only 3 options in "Change data source" dialog (1. Microsoft Access Database File (OLE DB) 2. Microsoft SQL Server Compact 3.5, 3. Microsoft SQL Server Database File) Any idea? Thanks in advice, Phil

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• midl.exe cannot load mscorlib.tlb

  - by Akash

  I'm trying to use midl to turn an idl file into a tlb. However, when I try I get this warning: warning MIDL2015: failed to load tlb in importlib : mscorlib.tlb and I then get a subsequent error: error MIDL2337 : unsatisfied forward declaration : _Object..... I'm certain that the error is due to the first warning. I've tried the same command on a different machine and it succeeds, so I know that the idl file is correct. I've tried uninstalling the .NET framework and reinstalling it in the hope that that would fix things, but it had no effect. So my question is, what do I need to fix on my machine to allow midl to locate mscorlib.tlb once more?

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• Lightning talk: Coderetreat

  - by Michael Williamson

  In the spirit of trying to encourage more deliberate practice amongst coders in Red Gate, Lauri Pesonen had the idea of running a coderetreat in Red Gate. Lauri and I ran the first one a few weeks ago: given that neither of us hadn’t even been to a coderetreat before, let alone run one, I think it turned out quite well. The participants gave positive feedback, saying that they enjoyed the day, wrote some thought-provoking code and would do it again. Sam Blackburn was one of the attendees, and gave a lightning talk to the other developers in one of our regular lightning talk sessions: In case you can’t watch the video, I’ve transcribed the talk below, although I’d recommend watching the video if you can — I didn’t have much time to do the transcribing! So, what is a coderetreat? So it’s not just something in Red Gate, there’s a website and everything, although it’s not a very big website. It calls itself a community network. The basic ideas behind coderetreat are: you’ve got one day, and you split it into one hour sections. You spend three quarters of that coding, and do a little retrospective at the end. You’re supposed to start fresh each, we were told to delete our code after every session. We were in pairs, swapping after each session, and we did the same task every time. In fact, Conway’s Game of Life is the only task mentioned anywhere that I find for coderetreat. So I don’t know what we’ll do next time, or if we’re meant to do the same thing again. There are some guiding principles which felt to us like restrictions, that you have to code in crazy ways to encourage better code. Final thing is that it’s supposed to be free for outsiders to join. It’s meant to be a kind of networking thing, where you link up with people from other companies. We had a pilot day with Michael and Lauri. Since it was basically the first time any of us had done anything like this, everybody was from Red Gate. We didn’t chat to anybody else for the initial one. The task was Conway’s Game of Life, which most of you have probably heard of it, all but one of us knew about it when did the coderetreat. I won’t got into the details of what it is, but it felt like the right size of task, basically one or two groups actually produced something working by the end of the day, and of course that doesn’t mean it’s necessarily a day’s work to produce that because we were starting again every hour. The task really drives you more than trying to create good code, I found. It was really tempting to try and get it working rather than stick to the rules. But it’s really good to stop and try again because there are so many what-ifs when you’ve finished writing something, “what if I’d done it this way?”. You can answer all those questions at a coderetreat because it’s not about getting a product out the door, it’s about learning and playing with ideas. So we had all these different practices we were trying. I’ll try and go through most of these. Single responsibility is this idea that everything should do just one thing. It was the very first session, we were still trying to figure out how do you go about the Game of Life? So by the end of forty-five minutes hadn’t produced very much for that first session. We were still thinking, “Do we start with a board, how do we represent all these squares? It can be infinitely big, help, this is getting really difficult!”. So, most of us didn’t really get anywhere on the first one. Although it was interesting that some people started with the board, one group started with the FateDecider class that decides whether things live or die. A sort of god class, but in a good way. They managed to implement all of the rules without even defining how the squares were arranged or anything like that. Another thing we tried was TDD (test-driven development). I’m sure most of you know what TDD is: Watch a test, watch it fail for the right reason Write code to pass the test, watch it pass Refactor, check the test still passes Repeat! It basically worked, we were able to produce code, but we often found the tests defined the direction that code went, which is obviously the idea of TDD. But you tend to find that by the time you’ve even written your first assertion, which is supposed to be the very first thing you write, because you write your tests backwards from the assertions back to the initial conditions, you’ve already constrained the logic of the code in some way by the time you’ve done that. You then get to this situation of, “Well, we actually want to go in a slightly different direction. Can we do this?”. Can we write tests that don’t constrain the architecture? Wrapping up all primitives: it’s kind of turtles all the way down. We had a Size, which has a Width and Height, which both derive from Dimension. You’ve got pages of code before you’ve even done anything. No getters and setters (use tell don’t ask instead): mocks and stubs for tests are required if you want to assert that your results are what you think they should be. You can’t just check the internal state of the code. And people found that really challenging and it made them think in a different way which I think is really good. Not having mutable state: that was kind of confusing because we weren’t quite sure what fitted within that rule and what didn’t, and I think we were trying too hard to follow the rule rather than the guideline. No if-statements: supposed to use polymorphism instead, but polymorphism still requires a factory with conditional behaviour. We did something really crazy to get around this: public T If(bool condition, Func<T> left, Func<T> right) { var dict = new Dictionary<bool, Func<T>> {{true, left}, {false, right}}; return dict[condition].Invoke(); } That is not really polymorphism, is it? For-loops: you can always replace a for-loop with recursion, but it doesn’t tend to make it any more readable unless it’s the kind of task that really lends itself to that. So it was interesting, it was good practice, but it wouldn’t make it easier it’s the kind of tree-structure algorithm where that would help. Having a limit on the number of levels of indentation: again, I think it does produce very nice, clean code, but it wasn’t actually a challenge because you just extract methods. That’s quite a useful thing because you can apply that to real code and say, “Okay, should this method really be going crazy like this?” No talking: we hated that. It’s like there’s two of you at a computer, and one of you is doing the typing, what does the other guy do if they’re not allowed to talk. The answer is TDD ping-pong – one person writes the tests, and then the other person writes the code to pass the test. And that creates communication without actually having to have discussion about things which is kind of cool. No code comments: just makes no difference to anything. It’s a forty-five minute exercise, so what are you going to put comments in code for? Finally, this is my fault. I discovered an entertaining way of doing the calculation that was kind of cool (using convolutions over the state of the board). Unfortunately, it turns out to be really hard to implement in C#, so didn’t even manage to work out how to do that convolution in C#. It’s trivial in some high-level languages, but you need something matrix-orientated for it to really work. That’s most of it, really. The thoughts that people went away with: we put down our answers to questions like “What have you learnt?” and “What surprised you?”, “How are you going to do things differently?”, and most people said redoing the problem is really, really good for understanding it properly. People hate having a massive legacy codebase that they can’t change, so being able to attack something three different ways in an environment where the end-product isn’t important: that’s something people really enjoyed. Pair-programming: also people said that they wanted to do more of that, especially with TDD ping-pong, where you write the test and somebody else writes the code. Various people thought different things about immutables, but most people thought they were good, they promote functional programming. And TDD people found really hard. “Tell, don’t ask” people found really, really hard and really, really, really hard to do well. And the recursion just made things trickier to debug. But most people agreed that coderetreats are really cool, and we should do more of them.

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• Caspol, VMs, Mapped Drives, VS2010

  - by Simon Woods

  Hi I have a VM (Win7 32 bit) with VS2010 installed. I have a drive mapped into it from the host machine (VM 64 bit), when I have some of my VS2010 projects and to where I am building them. One of my projects is looking to load an assembly. If I copy that assembly to a local drive, the program ruins fine. If I leave it on the mapped drive, then I get an error Exception is: FileLoadException - Could not load file or assembly 'file:///Z:\BusinessTier\bin\Debug\BusinessTier.dll I am unsure whether or not I need to run Caspol. There is another post on SO which pointed me to a post which indicated that VS2008 SP1+ removed the need for caspol wrt network drives, but I wondered if I still needed to because I am in a VM. I have tried running the following on the host machine in an attempt to give permissions to VS inside the VM, but to no avail C:\Windows\Microsoft.NET\Framework\v4.0.30128>caspol -m -ag 1.2 -url file://g:\* FullTrust where g:* is the drive being mapped into the VM (as drive z:) What am I missing (apart from understanding!) Thx Simon

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• DCOM: CoCreateInstanceEx returns E_ACCESSDENIED

  - by MOE37x3

  I'm working on a DCOM application with the server and client on two machines, both of which are running WinXP with Service Pack 2. On both machines, I'm logged in with the same username and password. When the client on one machine calls CoCreateInstanceEx, asking the other machine to start up the server application, it returns E_ACCESSDENIED. I tried going into the server app's component properties in dcomcnfg and giving full permisions to everyone for everything, but that didn't help. What do I need to do to allow this call to succeed? Update: When the server app is running on a Windows 2000 box, I do not get this error; CoCreateInstanceEx returns S_OK.

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• dll not loading- FileLoadException

  - by user576061

  The problem I am having is that I am getting a System.IO.FileLoadException when trying to load the RWLock.dll on a test box and Windows xp machines. This is the exception that is thrown when it tries to load the dll on the windows 2003 server machine (most likely 32 bit): System.IO.FileLoadException: A procedure imported by 'rwlock, Version=1.0.3889.27926, Culture=neutral, PublicKeyToken=null' could not be loaded. File name: 'rwlock, Version=1.0.3889.27926, Culture=neutral, PublicKeyToken=null' --- System.Runtime.InteropServices.COMException (0x8007007F): The specified procedure could not be found. (Exception from HRESULT: 0x8007007F)... However, we have not had any problems trying to run this on a Windows 2007 server machine (64 bit). Any ideas? Thanks in advance :)

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• SQL Server 2008 Restore from Backup fails with error 3241 'cannot process this media family'

  - by pearcewg

  I am attempting to backup a database from a SQL Server instance on one machine and restore it to another, and I am encountering the frequently discovered 'SQL Server cannot process this media family' error. Each of my instances are SQL Server 2008, but with different patch levels Restore: 10.0.2531.0 Backup: 10.0.1600.22 ((SQL_PreRelease).080709-1414 ) The restore DB is express. Not sure about the backup version. The backup version is on a virtual private server. The restore is on my development box. When I restore to a different database on the source (backup) server, it restores fine. Lots of stuff on google about this issue, some on stackoverflow about this issue, but nothing which is this exact situation. Any thoughts? It should be straightforward to do a backup and restore from one machine to another (having done this thousands of times in with SQL 6.5,7,2000,2005).

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• Clustering Basics and Challenges

  - by Karoly Vegh

  For upcoming posts it seemed to be a good idea to dedicate some time for cluster basic concepts and theory. This post misses a lot of details that would explode the articlesize, should you have questions, do not hesitate to ask them in the comments.  The goal here is to get some concepts straight. I can't promise to give you an overall complete definitions of cluster, cluster agent, quorum, voting, fencing, split brain condition, so the following is more of an explanation. Here we go. -------- Cluster, HA, failover, switchover, scalability -------- An attempted definition of a Cluster: A cluster is a set (2+) server nodes dedicated to keep application services alive, communicating through the cluster software/framework with eachother, test and probe health status of servernodes/services and with quorum based decisions and with switchover/failover techniques keep the application services running on them available. That is, should a node that runs a service unexpectedly lose functionality/connection, the other ones would take over the and run the services, so that availability is guaranteed. To provide availability while strictly sticking to a consistent clusterconfiguration is the main goal of a cluster.  At this point we have to add that this defines a HA-cluster, a High-Availability cluster, where the clusternodes are planned to run the services in an active-standby, or failover fashion. An example could be a single instance database. Some applications can be run in a distributed or scalable fashion. In the latter case instances of the application run actively on separate clusternodes serving servicerequests simultaneously. An example for this version could be a webserver that forwards connection requests to many backend servers in a round-robin way. Or a database running in active-active RAC setup.  -------- Cluster arhitecture, interconnect, topologies -------- Now, what is a cluster made of? Servers, right. These servers (the clusternodes) need to communicate. This of course happens over the network, usually over dedicated network interfaces interconnecting all the clusternodes. These connection are called interconnects.How many clusternodes are in a cluster? There are different cluster topologies. The most simple one is a clustered pair topology, involving only two clusternodes:  There are several more topologies, clicking the image above will take you to the relevant documentation. Also, to answer the question Solaris Cluster allows you to run up to 16 servers in a cluster. Where shall these clusternodes be placed? A very important question. The right answer is: It depends on what you plan to achieve with the cluster. Do you plan to avoid only a server outage? Then you can place them right next to eachother in the datacenter. Do you need to avoid DataCenter outage? In that case of course you should place them at least in different fire zones. Or in two geographically distant DataCenters to avoid disasters like floods, large-scale fires or power outages. We call this a stretched- or campus cluster, the clusternodes being several kilometers away from eachother. To cover really large distances, you probably need to move to a GeoCluster, which is a different kind of animal.  What is a geocluster? A Geographic Cluster in Solaris Cluster terms is actually a metacluster between two, separate (locally-HA) clusters.  -------- Cluster resource types, agents, resources, resource groups -------- So how does the cluster manage my applications? The cluster needs to start, stop and probe your applications. If you application runs, the cluster needs to check regularly if the application state is healthy, does it respond over the network, does it have all the processes running, etc. This is called probing. If the cluster deems the application is in a faulty state, then it can try to restart it locally or decide to switch (stop on node A, start on node B) the service. Starting, stopping and probing are the three actions that a cluster agent does. There are many different kinds of agents included in Solaris Cluster, but you can build your own too. Examples are an agent that manages (mounts, moves) ZFS filesystems, or the Oracle DB HA agent that cares about the database, or an agent that moves a floating IP address between nodes. There are lots of other agents included for Apache, Tomcat, MySQL, Oracle DB, Oracle Weblogic, Zones, LDoms, NFS, DNS, etc.We also need to clarify the difference between a cluster resource and the cluster resource group.A cluster resource is something that is managed by a cluster agent. Cluster resource types are included in Solaris cluster (see above, e.g. HAStoragePlus, HA-Oracle, LogicalHost). You can group cluster resources into cluster resourcegroups, and switch these groups together from one node to another. To stick to the example above, to move an Oracle DB service from one node to another, you have to switch the group between nodes, and the agents of the cluster resources in the group will do the following:  On node A Shut down the DB Unconfigure the LogicalHost IP the DB Listener listens on unmount the filesystem   Then, on node B: mount the FS configure the IP  startup the DB -------- Voting, Quorum, Split Brain Condition, Fencing, Amnesia -------- How do the clusternodes agree upon their action? How do they decide which node runs what services? Another important question. Running a cluster is a strictly democratic thing.Every node has votes, and you need the majority of votes to have the deciding power. Now, this is usually no problem, clusternodes think very much all alike. Still, every action needs to be governed upon in a productive system, and has to be agreed upon. Agreeing is easy as long as the clusternodes all behave and talk to eachother over the interconnect. But if the interconnect is gone/down, this all gets tricky and confusing. Clusternodes think like this: "My job is to run these services. The other node does not answer my interconnect communication, it must be down. I'd better take control and run the services!". The problem is, as I have already mentioned, clusternodes very much think alike. If the interconnect is gone, they all assume the other node is down, and they all want to mount the data backend, enable the IP and run the database. Double IPs, double mounts, double DB instances - now that is trouble. Also, in a 2-node cluster they both have only 50% of the votes, that is, they themselves alone are not allowed to run a cluster.  This is where you need a quorum device. According to Wikipedia, the "requirement for a quorum is protection against totally unrepresentative action in the name of the body by an unduly small number of persons.". They need additional votes to run the cluster. For this requirement a 2-node cluster needs a quorum device or a quorum server. If the interconnect is gone, (this is what we call a split brain condition) both nodes start to race and try to reserve the quorum device to themselves. They do this, because the quorum device bears an additional vote, that could ensure majority (50% +1). The one that manages to lock the quorum device (e.g. if it's an FC LUN, it SCSI reserves it) wins the right to build/run a cluster, the other one - realizing he was late - panics/reboots to ensure the cluster config stays consistent.  Losing the interconnect isn't only endangering the availability of services, but it also endangers the cluster configuration consistence. Just imagine node A being down and during that the cluster configuration changes. Now node B goes down, and node A comes up. It isn't uptodate about the cluster configuration's changes so it will refuse to start a cluster, since that would lead to cluster amnesia, that is the cluster had some changes, but now runs with an older cluster configuration repository state, that is it's like it forgot about the changes.  Also, to ensure application data consistence, the clusternode that wins the race makes sure that a server that isn't part of or can't currently join the cluster can access the devices. This procedure is called fencing. This usually happens to storage LUNs via SCSI reservation.  Now, another important question: Where do I place the quorum disk?  Imagine having two sites, two separate datacenters, one in the north of the city and the other one in the south part of it. You run a stretched cluster in the clustered pair topology. Where do you place the quorum disk/server? If you put it into the north DC, and that gets hit by a meteor, you lose one clusternode, which isn't a problem, but you also lose your quorum, and the south clusternode can't keep the cluster running lacking the votes. This problem can't be solved with two sites and a campus cluster. You will need a third site to either place the quorum server to, or a third clusternode. Otherwise, lacking majority, if you lose the site that had your quorum, you lose the cluster. Okay, we covered the very basics. We haven't talked about virtualization support, CCR, ClusterFilesystems, DID devices, affinities, storage-replication, management tools, upgrade procedures - should those be interesting for you, let me know in the comments, along with any other questions. Given enough demand I'd be glad to write a followup post too. Now I really want to move on to the second part in the series: ClusterInstallation.  Oh, as for additional source of information, I recommend the documentation: http://docs.oracle.com/cd/E23623_01/index.html, and the OTN Oracle Solaris Cluster site: http://www.oracle.com/technetwork/server-storage/solaris-cluster/index.html

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