Tanguy Leroux edf27a599e
Add new setting to disable persistent tasks allocations (#29137)
This commit adds a new setting `cluster.persistent_tasks.allocation.enable`
that can be used to enable or disable the allocation of persistent tasks.
The setting accepts the values `all` (default) or `none`. When set to
none, the persistent tasks that are created (or that must be reassigned)
won't be assigned to a node but will reside in the cluster state with
a no "executor node" and a reason describing why it is not assigned:

```
"assignment" : {
  "executor_node" : null,
  "explanation" : "persistent task [foo/bar] cannot be assigned [no
  persistent task assignments are allowed due to cluster settings]"
}
```
2018-03-22 09:18:07 +01:00
..