Put Follow API

Request

The Put Follow API allows creates a follower index and make that index follow a leader index.

PutFollowRequest putFollowRequest = new PutFollowRequest(
    "local", 
    "leader", 
    "follower", 
    ActiveShardCount.ONE 
);

The name of the remote cluster alias.

The name of the leader in the remote cluster.

The name of the follower index that gets created as part of the put follow API call.

The number of active shard copies to wait for before the put follow API returns a response, as an ActiveShardCount

Response

The returned PutFollowResponse indicates if the put follow request was received.

boolean isFollowIndexCreated =
    putFollowResponse.isFollowIndexCreated(); 
boolean isFollowIndexShardsAcked =
    putFollowResponse.isFollowIndexShardsAcked(); 
boolean isIndexFollowingStarted =
    putFollowResponse.isIndexFollowingStarted(); 

Whether the follower index was created.

Whether the follower shards are started.

Whether the follower index started following the leader index.

Synchronous Execution

When executing a PutFollowRequest in the following manner, the client waits for the PutFollowResponse to be returned before continuing with code execution:

PutFollowResponse putFollowResponse =
    client.ccr().putFollow(putFollowRequest, RequestOptions.DEFAULT);

Synchronous calls may throw an IOException in case of either failing to parse the REST response in the high-level REST client, the request times out or similar cases where there is no response coming back from the server.

In cases where the server returns a 4xx or 5xx error code, the high-level client tries to parse the response body error details instead and then throws a generic ElasticsearchException and adds the original ResponseException as a suppressed exception to it.

Asynchronous Execution

Executing a PutFollowRequest can also be done in an asynchronous fashion so that the client can return directly. Users need to specify how the response or potential failures will be handled by passing the request and a listener to the asynchronous ccr-put-follow method:

client.ccr().putFollowAsync(putFollowRequest,
    RequestOptions.DEFAULT, listener); 

The PutFollowRequest to execute and the ActionListener to use when the execution completes

The asynchronous method does not block and returns immediately. Once it is completed the ActionListener is called back using the onResponse method if the execution successfully completed or using the onFailure method if it failed. Failure scenarios and expected exceptions are the same as in the synchronous execution case.

A typical listener for ccr-put-follow looks like:

ActionListener<PutFollowResponse> listener =
    new ActionListener<PutFollowResponse>() {
        @Override
        public void onResponse(PutFollowResponse response) { 
            boolean isFollowIndexCreated =
                putFollowResponse.isFollowIndexCreated();
            boolean isFollowIndexShardsAcked =
                putFollowResponse.isFollowIndexShardsAcked();
            boolean isIndexFollowingStarted =
                putFollowResponse.isIndexFollowingStarted();
        }

        @Override
        public void onFailure(Exception e) {
            
        }
    };

Called when the execution is successfully completed.

Called when the whole PutFollowRequest fails.