Nomad will by default attempt to restart a job locally on the node that it is running or scheduled to be running on. These defaults vary by the scheduler type in use for the job: system, service, or batch.
To customize this behavior, the task group can be annotated with configurable
options using the
restart stanza. Nomad will restart the failed
task up to
attempts times within a provided
interval. Operators can also
choose whether to keep attempting restarts on the same node, or to fail the task
so that it can be rescheduled on another node, via the
Setting mode to
fail in the restart stanza allows rescheduling to occur
potentially moving the task to another node and is best practice.
The following CLI example shows job status and allocation status for a failed
task that is being restarted by Nomad. Allocations are in the
while restarts are attempted. The
Recent Events section in the CLI shows
ongoing restart attempts.
$ nomad job status demo ID = demo Name = demo Submit Date = 2018-04-12T14:37:18-05:00 Type = service Priority = 50 Datacenters = dc1 Status = running Periodic = false Parameterized = false Summary Task Group Queued Starting Running Failed Complete Lost demo 0 3 0 0 0 0 Allocations ID Node ID Task Group Version Desired Status Created Modified ce5bf1d1 8a184f31 demo 0 run pending 27s ago 5s ago d5dee7c8 8a184f31 demo 0 run pending 27s ago 5s ago ed815997 8a184f31 demo 0 run pending 27s ago 5s ago
In the following example, the allocation
ce5bf1d1 is restarted by Nomad
approximately every ten seconds, with a small random jitter. It eventually
reaches its limit of three attempts and transitions into a
failed state, after
which it becomes eligible for rescheduling.
$ nomad alloc status ce5bf1d1 ID = ce5bf1d1 Eval ID = 64e45d11 Name = demo.demo Node ID = a0ccdd8b Job ID = demo Job Version = 0 Client Status = failed Client Description = <none> Desired Status = run Desired Description = <none> Created = 56s ago Modified = 22s ago Task "demo" is "dead" Task Resources CPU Memory Disk Addresses 100 MHz 300 MiB 300 MiB Task Events: Started At = 2018-04-12T22:29:08Z Finished At = 2018-04-12T22:29:08Z Total Restarts = 3 Last Restart = 2018-04-12T17:28:57-05:00 Recent Events: Time Type Description 2018-04-12T17:29:08-05:00 Not Restarting Exceeded allowed attempts 3 in interval 5m0s and mode is "fail" 2018-04-12T17:29:08-05:00 Terminated Exit Code: 127 2018-04-12T17:29:08-05:00 Started Task started by client 2018-04-12T17:28:57-05:00 Restarting Task restarting in 10.364602876s 2018-04-12T17:28:57-05:00 Terminated Exit Code: 127 2018-04-12T17:28:57-05:00 Started Task started by client 2018-04-12T17:28:47-05:00 Restarting Task restarting in 10.666963769s 2018-04-12T17:28:47-05:00 Terminated Exit Code: 127 2018-04-12T17:28:47-05:00 Started Task started by client 2018-04-12T17:28:35-05:00 Restarting Task restarting in 11.777324721s