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