-
Notifications
You must be signed in to change notification settings - Fork 42.9k
PreStart and PostStop event hooks #140
Copy link
Copy link
Closed
Labels
area/dockerarea/kubeletkind/featureCategorizes issue or PR as related to a new feature.Categorizes issue or PR as related to a new feature.lifecycle/frozenIndicates that an issue or PR should not be auto-closed due to staleness.Indicates that an issue or PR should not be auto-closed due to staleness.priority/awaiting-more-evidenceLowest priority. Possibly useful, but not yet enough support to actually get it done.Lowest priority. Possibly useful, but not yet enough support to actually get it done.sig/nodeCategorizes an issue or PR as relevant to SIG Node.Categorizes an issue or PR as relevant to SIG Node.
Description
Metadata
Metadata
Assignees
Labels
area/dockerarea/kubeletkind/featureCategorizes issue or PR as related to a new feature.Categorizes issue or PR as related to a new feature.lifecycle/frozenIndicates that an issue or PR should not be auto-closed due to staleness.Indicates that an issue or PR should not be auto-closed due to staleness.priority/awaiting-more-evidenceLowest priority. Possibly useful, but not yet enough support to actually get it done.Lowest priority. Possibly useful, but not yet enough support to actually get it done.sig/nodeCategorizes an issue or PR as relevant to SIG Node.Categorizes an issue or PR as relevant to SIG Node.
Many systems support event hooks for extensions. A few examples:
https://developers.google.com/appengine/docs/java/javadoc/com/google/appengine/api/LifecycleManager
http://developer.android.com/guide/components/activities.html
http://upstart.ubuntu.com/cookbook/#event
https://coreos.com/docs/launching-containers/launching/getting-started-with-systemd/
http://elasticbox.com/documentation/configuring-and-managing-boxes/start-stop-and-upgrade-boxes/
http://git-scm.com/docs/githooks.html
docker stop and restart currently send SIGTERM followed by SIGKILL, similar to many other systems (e.g., Heroku: https://devcenter.heroku.com/articles/dynos#graceful-shutdown-with-sigterm), which provides an opportunity for applications to cleanly shut down, but lacks the ability to communicate the grace period duration or termination reason and doesn't directly provide support for notifying other processes or services.
As described in the (liveness probe issue)[https://github.com//issues/66], it would be useful to support multiple types of hook execution/notification mechanisms. It would also be useful to pass arguments from clients, such as "reason" (e.g., "cancel", "restart", "reload", "resize", "reboot", "move", "host_update", "probe_failure"). Another way "reason" could be handled is with user-defined events.
In addition to pre-termination notification, we should define other lifecycle hook points, probably at least pre- and post- start and terminate.
It would be useful for post-terminate to be passed the (termination reason)[https://github.com//issues/137], which could either be successful completion, a client-provided stop reason (see above), or detailed failure reason (exit, signal, OOM, container creation error, docker crash, machine crash, lost/ghost).
If the application generated an assertion failure or exception message, a post-termination hook could copy it to (/run/status.txt)[https://github.com//issues/139].
It would also be useful to be able to control (restart behavior)[https://github.com//issues/127] from a hook. We'd need a convenient way to carry over state from a previous execution. The simplest starting point would be for the user to keep it in a (volume)[https://github.com//issues/97].