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docs for stop_on_client_disconnect stanza (#7938)

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Tim Gross
2020-05-13 16:39:24 -04:00
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website/pages/docs/job-specification/group.mdx
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@@ -68,6 +68,20 @@ job "docs" {
own [`shutdown_delay`](/docs/job-specification/task#shutdown_delay)
which waits between deregistering task services and stopping the task.
- `stop_after_client_disconnect` `(string: "")` - Specifies a duration
after which a Nomad client that cannot communicate with the servers
will stop allocations based on this task group. By default, a client
will not stop an allocation until explicitly told to by a server. A
client that fails to heartbeat to a server within the
`hearbeat_grace` window and any allocations running on it will be
marked "lost" and Nomad will schedule replacement
allocations. However, these replaced allocations will continue to
run on the non-responsive client; an operator may desire that these
replaced allocations are also stopped in this case — for example,
allocations requiring exclusive access to an external resource. When
specified, the Nomad client will stop them after this duration. The
Nomad client process must be running for this to occur.
- `task` <code>([Task][]: &lt;required&gt;)</code> - Specifies one or more tasks to run
within this group. This can be specified multiple times, to add a task as part
of the group.
@@ -129,12 +143,55 @@ group "example" {
}
```
### Stop After Client Disconnect
This example shows how `stop_after_client_disconnect` interacts with
other stanzas. For the `first` group, after the default 10 second
[`heartbeat_grace`] window expires and 90 more seconds passes, the
server will reschedule the allocation. The client will wait 90 seconds
before sending a stop signal (`SIGTERM`) to the `first-task`
task. After 15 more seconds because of the task's `kill_timeout`, the
client will send `SIGKILL`. The `second` group does not have
`stop_after_client_disconnect`, so the server will reschedule the
allocation after the 10 second [`heartbeat_grace`] expires. It will
not be stopped on the client, regardless of how long the client is out
of touch.
Note that if the server's clocks are not closely synchronized with
each other, the server may reschedule the group before the client has
stopped the allocation. Operators should ensure that clock drift
between servers is as small as possible.
Note also that a group using this feature will be stopped on the
client if the Nomad server cluster fails, since the client will be
unable to contact any server in that case. Groups opting in to this
feature are therefore exposed to an additional runtime dependency and
potential point of failure.
```hcl
group "first" {
stop_after_client_disconnect = "90s"
task "first-task" {
kill_timeout = "15s"
}
}
group "second" {
task "second-task" {
kill_timeout = "5s"
}
}
```
[task]: /docs/job-specification/task 'Nomad task Job Specification'
[job]: /docs/job-specification/job 'Nomad job Job Specification'
[constraint]: /docs/job-specification/constraint 'Nomad constraint Job Specification'
[spread]: /docs/job-specification/spread 'Nomad spread Job Specification'
[affinity]: /docs/job-specification/affinity 'Nomad affinity Job Specification'
[ephemeraldisk]: /docs/job-specification/ephemeral_disk 'Nomad ephemeral_disk Job Specification'
[`heartbeat_grace`]: /docs/configuration/server/#heartbeat_grace
[meta]: /docs/job-specification/meta 'Nomad meta Job Specification'
[migrate]: /docs/job-specification/migrate 'Nomad migrate Job Specification'
[reschedule]: /docs/job-specification/reschedule 'Nomad reschedule Job Specification'