Hi Richard, thanks for reporting the issue. Is there anything that I should be aware with regards to your build/steps? I'm asking because since JENKINS-18094 (version 1.0.8) if you receive "Xvfb failed to start, consult the lines above for errors" message in the console log your build will inevitably be aborted due to RunnerAbortedException being thrown immediately after.
If you indeed are running version 1.0.8 could you create a sample build job and attach it to this issue.

Thanks

Zoran

Well, this is embarrassing. I'm having difficulty setting up a test job that replicates the issue. With Xvfb configured and a single, simple shell command as the build task, the build aborts if a display is already taken (I run the same display at the command line.

In my example above, the issue I was getting is this: http://www.x.org/wiki/FAQErrorMessages/#index6h2 which is slightly harder to replicate manually.

Ok - I've replicated the issue. It happens when Xvfb's lock file is removed, but the display is still running.

1. Start a display on Jenkins Slave: /usr/bin/Xvfb :1972 -screen 0 1024x768x24 &
2. Remove the corresponding lock file: rm -rf /tmp/.X1972-lock
3. Run a simply Jenkins job that starts Xvfb on display 1972, with a single build task (e.g. a
4. Run build job

Build job passes successfully, even though the Xvfb plugin logs an error.

Started by user Cross, Richard (Contractor)
[EnvInject] - Loading node environment variables.
Building remotely on appduvirtual0c9 in workspace /buildstore/jenkins_appduvirtual0c9_slave/workspace/Xvfb_test_failure_scenario
Xvfb starting$ /usr/bin/Xvfb :1972 -screen 0 1024x768x24 -fbdir /buildstore/jenkins_appduvirtual0c9_slave/2014-02-03_12-23-504926962666561200040xvfb
_XSERVTransSocketINETCreateListener: ...SocketCreateListener() failed
_XSERVTransMakeAllCOTSServerListeners: server already running

Fatal server error:
Cannot establish any listening sockets - Make sure an X server isn't already running
unlink: No such file or directory
unlink failed, Invalid argument[Xvfb_test_failure_scenario] $ /bin/sh -xe /tmp/hudson7411154595497137988.sh
+ echo This should only run is Xvfb is successful.
This should only run is Xvfb is successful.
Xvfb stopping
Notifying upstream projects of job completion
Finished: SUCCESS

Richard, thanks the detailed steps needed to reproduce this. I'm getting more or less the same output on my test setup but unlike in your case the build fails. This is what I got:

Building remotely on ubuntu
Xvfb starting$ /usr/bin/Xvfb :1111 -screen 0 1024x768x24 -fbdir /tmp/jenkins/2014-02-03_20-51-241837796366101415022xvfb
_XSERVTransSocketINETCreateListener: ...SocketCreateListener() failed
_XSERVTransMakeAllCOTSServerListeners: server already running
(EE) 
Fatal server error:
(EE) Cannot establish any listening sockets - Make sure an X server isn't already running(EE) 
unlink: No such file or directory
unlink  failed, Invalid argument
ERROR: Xvfb failed to start, consult the lines above for errors
Finished: FAILURE

I'm running this slave on Ubuntu 13.10 with Xvfb from x.org/freedesktop.org version 1.14.3.

I did notice that your last console log does not contain the "ERROR: Xvfb failed to start, consult the lines above for errors" line, was it missing from the output?

The way the plugin checks if Xvfb started successfully is to see if the Xvfb process is alive, it could be that in your case there is a race condition between this check and the Xvfb terminating. To help with these situations you have an option to set the timeout value (the "Timeout in seconds" option in the advanced settings), where 0 is no timeout. Try setting timeout to 1 or 2 seconds and see if the launch failure of Xvfb is properly detected.

Another alternative would be to let Xvfb choose its own display number, the way it does this is to try and find a free port to listen on, so it would not start on the same port as another X server.

Thanks for the suggestion; I'll try it out when I'm back in the office.

By the way, I only hard coded the display number in this job order to replicate the fault. In our live build jobs of course, the display number is left to auto-select, with a high offset to avoid collisions with other processes that require displays.

Local race condition, closing