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In this section, we’ll look at exactly what happens during a fail over.
In this release of Jenkins Enterprise, a fail-over is effectively (1) shutting down the current Jenkins master, followed by (2) starting it up in another location. Sometimes the step 1 doesn’t happen, for example when the current master becomes unresponsive. Because these masters work with the same $JENKINS_HOME, this fail over has the following characteristics:
- Jenkins global settings, configuration of jobs/users, fingerprints, record of completed builds (including archived artifacts, test reports, etc.), will all survive a fail-over.
- Builds that were in progress will normally not survive a fail-over, although their records will survive. Normally no attempt will be made to re-execute those builds, though Restart Aborted Builds can do so. Long-running builds may also be used in case aborting builds would be problematic.
- User sessions are lost. If your Jenkins installation requires users to log in, they’ll be asked to log in again.
- During the startup phase of the fail-over, Jenkins will not be able to serve inbound requests or builds. Therefore, a fail-over typically takes a few minutes, not a few seconds.