ClusterStateApplier (server 7.5.2 API)

All Known Implementing Classes:

IndicesClusterStateService, IngestActionForwarder, IngestService, RepositoriesService, RestoreService, ScriptService, SnapshotsService, TaskManager
```
public interface ClusterStateApplier
```
A component that is in charge of applying an incoming cluster state to the node internal data structures. The single apply method is called before the cluster state becomes visible via ClusterService.state().

- Method Summary
  
  Modifier and Type Method Description
  
  void applyClusterState(ClusterChangedEvent event)
  Called when a new cluster state (ClusterChangedEvent.state() needs to be applied.

- Method Detail
  - applyClusterState
```
void applyClusterState(ClusterChangedEvent event)
```
    Called when a new cluster state (ClusterChangedEvent.state() needs to be applied. The cluster state to be applied is already committed when this method is called, so an applier must therefore be prepared to deal with any state it receives without throwing an exception. Throwing an exception from an applier is very bad because it will stop the application of this state before it has reached all the other appliers, and will likely result in another attempt to apply the same (or very similar) cluster state which might continue until this node is removed from the cluster.