Nomad
Define restart behavior in your jobs
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 mode parameter.
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 pending state
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[1]
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