This adds support for two enhancements to swarm service rolling updates:
- Failure thresholds: In Docker 1.12, a service update could be set up
to either pause or continue after a single failure occurs. This adds
an --update-max-failure-ratio flag that controls how many tasks need to
fail to update for the update as a whole to be considered a failure. A
counterpart flag, --update-monitor, controls how long to monitor each
task for a failure after starting it during the update.
- Rollback flag: service update --rollback reverts the service to its
previous version. If a service update encounters task failures, or
fails to function properly for some other reason, the user can roll back
the update.
SwarmKit also has the ability to roll back updates automatically after
hitting the failure thresholds, but we've decided not to expose this in
the Docker API/CLI for now, favoring a workflow where the decision to
roll back is always made by an admin. Depending on user feedback, we may
add a "rollback" option to --update-failure-action in the future.
Signed-off-by: Aaron Lehmann <aaron.lehmann@docker.com>
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