When a Release is promoted, new Processes are gracefully rolled out to avoid disruption to the App.
How it Works
The rolling update proceeds in a “make one, break one” process in order to maintain Service uptime and capacity.
- Start 1 new Process on the new Release
- Verify that the new Process passes a health check
- Stop 1 old Process that is running the old Release
- Repeat until all Processes are running the new Release
Minimum / Maximum configuration
Rolling updates will respect the deployment configuration to control the minimum number of healthy processes and maximum number of overall processes to have running at any one time during the update. This defaults to a minimum of 50% and a maximum of 200%.
If any of the following conditions occur while the new Release is being rolled out, the rollout will reverse and return all Processes to the original Release:
- A Process fails to start up and listen on the expected port
- A Process fails to pass a health check
Any of these issues will appear in the logs that display during the promotion to help you determine what is going wrong.
See Troubleshooting for some tips on diagnosing common failure cases.