We've decided to allow arbitrary signal rewriting, not just SIGTERM
rewriting. To use, call dumb-init with the '-r s:r' option, which will
rewrite signum s to signum r. Only signals 1-31 are allowed to be
rewritten, which should cover all the signals we need to cover.
Note that this commit does not add new tests, it only fixes the existing
broken test.
Many servers respond to other signals than SIGTERM for their "soft
shutdown" option, such as Unicorn which requires SIGQUIT to wait on
outstanding connections. The 'docker stop' command sends the SIGTERM
signal to the container, and provides no option for modifying this
behavior. The 'docker kill' command has an '-s' option which allows one
to modify the signal sent to the container, but orchestration frameworks
such as Mesos don't provide a way to use this functionality.
This commit adds the '-s/--signal' option to dumb-init, which provides a
replacement signal for SIGTERM. For instance, running dumb-init like so:
dumb-init -s 3 <command>
Will send SIGQUIT (3) to the <command> process it spawns when it
receives a SIGTERM. This allows Docker image writers the freedom to
specify how SIGTERM will behave in their containers.
A further improvement to this option could be to provide an arbirary
mapping from signal to signal, but that would greatly complicate the
code for a probably minor use case.
