[feature request] Allow user defined stop hook

[stevendanna]

Occasionally, properly shutting down a service requires something other than simply sending a SIGTERM. For example, we would like our default PostgreSQL shutdown behavior to be the "Fast Shutdown" that is documented here:

https://www.postgresql.org/docs/9.6/static/server-shutdown.html

Other process supervisors such as runit allow users to customize the shutdown behavior (http://smarden.org/runit/runsv.8.html). It would be good if Habitat allowed something similar.

A stop hook would fit in nicely with the existing lifecycle hooks.

The stop hook would also benefit from a documented and supported way to reference the main PID under supervision.

[baumanj]

Still valid, post v0.56

[gfodor]

I have a similar issue here, proposing a number of hooks: #4923

[HT154]

If I'm understanding this correctly, then I think core/rabbitmq already does something like this, albeit in a roundabout way:

https://github.com/habitat-sh/core-plans/blob/22ee0017e85611b756bdfb7a3ad8e3fe35c994e0/rabbitmq/hooks/run#L32-L37

[stevendanna]

For the stop hook to be useful, my guess is we will also need a configurable timeout as described in #2447

[stale]

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[stevendanna]

While the configurable signal and timeout that was added cover many use cases, I still think we should consider supporting stop hooks or close this with a clear statement of why we don't want them.

A number of services create their own "stop" hooks by installing a signal handler as part of their run hook.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. We value your input and contribution. Please leave a comment if this issue still affects you.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. We value your input and contribution. Please leave a comment if this issue still affects you.