HHVM/Troubleshooting

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Problem determination and data collection

  • hhvmadm check-health: emits useful statistics like load, queued reqs, etc..
  • hhvm-dump-debug: captures a stack trace of HHVM and writes it to stdout and to /tmp/hhvm.$PID.bt. Run hhvm-dump-debug --full to generate a core dump as well.
  • links -dump http://127.0.0.1/server-status -width 80: produce a full Apache status report, showing which requests are currently in flight.
  • furl is a cURL-like tool for FastCGI. You can use it to bypass Apache and request pages directly from HHVM. For example: furl http://en.wikipedia.org/wiki/Main_Page. Requests always go to localhost.
  • curl localhost:9002/dump-apc will dump all the current APC keys to /tmp/apc_dump.
  • stacktraces, if available, are in /var/log/hhvm
  • core dumps are in /var/tmp/core or sysctl kernel.core_pattern

Light process dying

If you see light processes deaths in the logs it could be because they always log when they exit (noisy but ignorable). Please check the parent page for an explanation of what a light process is.