TFS： 解决The build agent error - the session for this agent already exists

来源：http://ericphan.net/blog/2016/6/10/solving-the-tfs-build-agent-error-the-session-for-this-agent-already-exists

Recently we've been getting the following error for our TFS build agents which caused all our builds to fail

Figure: TFS Builds are failing

The error reported is "The job has been abandoned because agent <agent name> did not renew the lock. Ensure agent is running, not sleeping, and has not lost communication with the service."

Investigating the _diag folder of the build agent itself reveals the actual error.

---------------------------------------------------------------------------
The session for this agent already exists. Sleeping for 30 seconds before next retry. Attempts=1/10.
---------------------------------------------------------------------------
Microsoft.TeamFoundation.DistributedTask.WebApi.TaskAgentSessionConflictException: The task agent Agent-SYDTFSBLDP01-1 already has an active session for owner SYDTFSBLDP01.
   at Microsoft.VisualStudio.Services.WebApi.VssHttpClientBase.HandleResponse(HttpResponseMessage response)
   at Microsoft.VisualStudio.Services.WebApi.VssHttpClientBase.<SendAsync>d__79.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.Services.WebApi.VssHttpClientBase.<SendAsync>d__76`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.Services.WebApi.VssHttpClientBase.<SendAsync>d__65`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.Services.WebApi.VssHttpClientBase.<SendAsync>d__64`1.MoveNext()
  at Microsoft.VisualStudio.Services.WebApi.VssHttpClientBase.HandleResponse(HttpResponseMessage response)
   at Microsoft.VisualStudio.Services.WebApi.VssHttpClientBase.<SendAsync>d__79.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.Services.WebApi.VssHttpClientBase.<SendAsync>d__76`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.Services.WebApi.VssHttpClientBase.<SendAsync>d__65`1.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at Microsoft.VisualStudio.Services.WebApi.VssHttpClientBase.<SendAsync>d__64`1.MoveNext()

To fix this issue, you need to re-run the ConfigureAgent.cmd and on the first option "Do you want to also replace the server registration (default is N)" Choose "Y"

（这里我遇到的情况略有不同，我用到的ConfigureAgent文件的后缀是ps1，即是powershell文件，故需要以管理员权限打开powershell，然后运行ConfigureAgent）

PS C:\Agents\2> .\ConfigureAgent.cmd
An existing configuration file was detected.  This will update the local agent settings.  Do you want to also replace th
e server registration (default is N)? Y

This will remove the existing agent registration and clean up the locked "session".