I had this problem at work when running php unit tests on Jenkins (CI server) and it took the whole team ages to figure out this problem. I thought it’s something worth sharing.
We use Jenkins to run ant which invokes our unit tests and to speed up the process we are running all the unit tests in one single process (this means we are not doing phpunit –process-isolation which runs each test in a separate PHP process. The up side of using this option is it uses a lot less memory, but the down side is it’s significantly slower). The whole process consumes around 500 mb of memory in one single process but one day we started getting the following error,
<http://jenkins/project/build.xml>:245: The following error occurred while executing this line:
/path..to..build/build.xml:66: exec returned: 137
We thought it might be something related to memory but we weren’t sure about it until one day we checked the kernel log (by typing in dmesg) and we get,
Out of memory: Kill process 16394 (phpunit) score 193 or sacrifice child
Killed process 16394, UID 497, (phpunit) total-vm:791308kB, anon-rss:348416kB, file-rss:4kB
And we know it’s memory related for sure, after increased the virtual memory allowance to 4G, it solved the problem.
However if you don’t have the luxury to increase your memory limit, try to use the –process-isolation option which would only use a tiny amount of memory to run all the tests but I found this takes 5-6 times longer to run all tests.
Hope this helps.