Wednesday, January 28, 2015

Resolving "The agent process was stopped while the test was running" on a TFS build agent

I'm currently working on a project that uses TFS for automated builds. Recently, our builds started failing with the error "The agent process was stopped while the test was running" while running unit tests. It wouldn't always happen during the same test, though it did frequently.

After inspecting the Event Viewer on the build machines, we found an error in the .NET Runtime that was taking down the build agent:

Application: QTAgent32_40.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: Moq.MockException
   at System.Runtime.CompilerServices.AsyncMethodBuilderCore.<ThrowAsync>b__5(System.Object)
   at System.Threading.QueueUserWorkItemCallback.WaitCallback_Context(System.Object)
   at System.Threading.ExecutionContext.RunInternal(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
   at System.Threading.ExecutionContext.Run(System.Threading.ExecutionContext, System.Threading.ContextCallback, System.Object, Boolean)
   at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()
   at System.Threading.ThreadPoolWorkQueue.Dispatch()
   at System.Threading._ThreadPoolWaitCallback.PerformWaitCallback()
The exception that was being thrown on a ThreadPoolThread (always extremely bad, never good) was a MockException: our unit testing framework was throwing an exception that was taking down the build agent.  But where?

How We Solved It

By some miracle, one of our developers decided to run our problematic tests with mstest on the command line on his local machine. As it turns out, this was great because it showed the stack traces for the loose threads on the command line. Turns out we had a lot more loose threads than just the one that was taking down our test agent on the build machine. The command the developer used was (similar to) the following:

mstest.exe /testcontainer:"C:\path\to\my\test.dll" /noisolation

After auditing all of the errors by rooting them out with command line runs of mstest, the solutions to our problems all boiled down to one thing:

*ALWAYS* wrap the contents of 'async void' methods with a try-catch block!

Thursday, January 22, 2015

Implementing a WCF service on an Active Directory domain using a ServiceHost in a Windows Service with Windows authentication and a non-system user service account

So, as it turns out, when you want to implement a WCF service on an Active Directory domain using a ServiceHost in a Windows Service with Windows authentication and a non-system user service account, you have to jump through a few hoops for the configuration. I kept getting the error message "A call to SSPI failed. see inner exception". The inner exception is "The target principal name is incorrect.". Like many other people, I kept thinking it had to do with authentication of the *client*. As it turns out, like those other people, I was wrong. It was to do with *verification of the service account running the service*. This is presumably because the *service user is a domain user service account*. To get this scenario working, you have to specify the name of the service user account as the 'userPrincipalName' in the 'identity' element of the 'endpoint' element for your service, like so:

<service name="MyProject.MyService">
<add baseAddress="net.tcp://localhost:12345/MyService"/>
<endpoint name="MyServiceTcpEndpoint"
<userPrincipalName value="MyDomainName\MyServiceUserName"/>
<endpoint address="mex" binding="mexTcpBinding" contract="IMetadataExchange" />
<binding name="MyServiceTcpBinding"
<security mode="Transport">
<!-- Use Windows authentication to ensure that we at least have authentication if not encryption -->
<transport clientCredentialType="Windows" />
Now you'll get proper connections and authentication via Windows.

Adding files generated at build time to your ClickOnce deployment

So, it used to be that I didn't really like ClickOnce deployment, but it turns out it has a lot of benefits:

  • It provides infrastructure that makes it *exceedingly* easy for your average lay-user to upgrade. All they have to do is start the program as normal, and it automatically updates for them (when configured properly)
  • It bundles everything up nicely and is easy to install and uninstall (if you're a real person. If you're a script, not so much)
I recently encountered the problem of including files generated at build time (e.g. transformed configuration files) in the ClickOnce deployment package. I found the following that I could include in my ClickOnce project's .csproj MSBuild file:

 <Content Include="Path\To\My.file" Condition=" Exists('Path\To\My.file') ">
 The key part to getting it to work properly is that your build has to do a Build target first, then a Publish target (usually with two separate invocations of MSBuild via a build script, rather than building with a Solution). Fortunately, I was already set up for that, so getting the extra files included was a dream.

Friday, January 16, 2015

Querying XML with namespaces in PowerShell

Apparently it's ridiculously easy to parse XML in PowerShell once you have the right objects set up:

[xml] $xml = Get-Content .\DeploymentProfile.PRODUCTION.xml
$ns = new-object Xml.XmlNamespaceManager $xml.NameTable
$ns.AddNamespace('dns', '')
$xml.SelectNodes("//@dns:ServerHostName", $ns) | ForEach-Object { $_.Value } | sort | Get-Unique

In this example, I query a deployment configuration for attributes called "ServerHostName" within the XML namespace "". This was exceptionally useful today when I quickly needed to figure out what servers my system was using and send that information to others to configure those servers.

Implementing Code Analysis with Team Foundation Server 2012 and later

I've been looking to get Code Analysis going on our team project at work. I found this helpful MSDN article.

Adding a computer to the local machine's list of PowerShell TrustedHosts

Retrieve the current list:

$curValue = (get-item wsman:\localhost\Client\TrustedHosts).value

Set the new list, appending the new host onto the old list:

set-item wsman:\localhost\Client\TrustedHosts -value "$curValue,"