1/*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements.  See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License.  You may obtain a copy of the License at
8 *
9 *    http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18package org.apache.spark.deploy.master
19
20import org.apache.spark.annotation.DeveloperApi
21
22/**
23 * :: DeveloperApi ::
24 *
25 * A LeaderElectionAgent tracks current master and is a common interface for all election Agents.
26 */
27@DeveloperApi
28trait LeaderElectionAgent {
29  val masterInstance: LeaderElectable
30  def stop() {} // to avoid noops in implementations.
31}
32
33@DeveloperApi
34trait LeaderElectable {
35  def electedLeader(): Unit
36  def revokedLeadership(): Unit
37}
38
39/** Single-node implementation of LeaderElectionAgent -- we're initially and always the leader. */
40private[spark] class MonarchyLeaderAgent(val masterInstance: LeaderElectable)
41  extends LeaderElectionAgent {
42  masterInstance.electedLeader()
43}
44