How to run long-running post-receive hook script in the background on Bitbucket Server and Data Center
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Summary
This article explains how to run long-running post-receive hook script in the background on Bitbucket Server and Data Center installations.
If Bitbucket is configured to use a post-receive hook script that is calling a long-running program, this program will block the hook script, and Bitbucket will log the alert message "Slow hook script detected" to atlassian-bitbucket-alerts.log.
To ensure that Bitbucket will not wait for this long-running program to finish, it must be run as a daemon in the background.
Environment
8.11, but also applicable to other versions.
Solution
Calling another script from the main hook script with added "&" does not work. Bitbucket still waits for all process' children to complete before considering hook execution completed.
What should be done here is to daemonize the long-running program. This can be done directly inside that program's code, but we can also do this using a small shell wrapper; the idea for this one-liner comes from https://stackoverflow.com/a/49183740:
( cd /; umask 0; setsid ${SCRIPT} </dev/null &>/dev/null & ) &SCRIPThere points to the program we want to daemonize.- It is possible to pass parameters to
SCRIPT.
The most important points that we are doing here are:
- We make a subshell using parenthesis and start that subshell in the background.
- By "setsid" we make a new process-group session.
- We close new script's STDIN, STDOUT, STDERR.
- Changing the working directory to "/" and setting umask are not important in this case; they are included here because both are considered part of good practice when daemonizing processes.