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/*
* Licensed to Elasticsearch under one or more contributor
* license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright
* ownership. Elasticsearch licenses this file to you under
* the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.elasticsearch.cluster;
/**
* Enables listening to master changes events of the local node (when the local node becomes the master, and when the local
* node cease being a master).
*/
public interface LocalNodeMasterListener {
/**
* Called when local node is elected to be the master
*/
void onMaster();
/**
* Called when the local node used to be the master, a new master was elected and it's no longer the local node.
*/
void offMaster();
/**
* The name of the executor that the implementation of the callbacks of this lister should be executed on. The thread
* that is responsible for managing instances of this lister is the same thread handling the cluster state events. If
* the work done is the callbacks above is inexpensive, this value may be
* {@link org.elasticsearch.threadpool.ThreadPool.Names#SAME SAME} (indicating that the callbacks will run on the same thread
* as the cluster state events are fired with). On the other hand, if the logic in the callbacks are heavier and take
* longer to process (or perhaps involve blocking due to IO operations), prefer to execute them on a separate more appropriate
* executor (eg. {@link org.elasticsearch.threadpool.ThreadPool.Names#GENERIC GENERIC}
* or {@link org.elasticsearch.threadpool.ThreadPool.Names#MANAGEMENT MANAGEMENT}).
*
* @return The name of the executor that will run the callbacks of this listener.
*/
String executorName();
}