| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF 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.apache.activemq.artemis.core.server.cluster.qourum; |
| |
| import org.apache.activemq.artemis.api.core.SimpleString; |
| import org.apache.activemq.artemis.core.client.impl.Topology; |
| import org.apache.activemq.artemis.core.persistence.StorageManager; |
| |
| import java.util.concurrent.CountDownLatch; |
| import java.util.concurrent.TimeUnit; |
| |
| /** |
| * A Qourum Vote for deciding if a replicated backup should become live. |
| */ |
| public class QuorumVoteServerConnect extends QuorumVote<BooleanVote, Boolean> { |
| |
| private static final SimpleString LIVE_FAILOVER_VOTE = new SimpleString("LIVE_FAILOVER)VOTE"); |
| private final CountDownLatch latch; |
| |
| private int votesNeeded; |
| |
| private int total = 0; |
| |
| private boolean decision = false; |
| |
| /** |
| * live nodes | remaining nodes | majority | votes needed |
| * 1 | 0 | 0 | 0 |
| * 2 | 1 | 1 | 1 |
| * n | r = n-1 | n/2 + 1 | n/2 + 1 rounded |
| * 3 | 2 | 2.5 | 2 |
| * 4 | 3 | 3 | 3 |
| * 5 | 4 | 3.5 | 3 |
| * 6 | 5 | 4 | 4 |
| */ |
| public QuorumVoteServerConnect(int size, StorageManager storageManager) { |
| super(LIVE_FAILOVER_VOTE); |
| double majority; |
| if (size <= 2) { |
| majority = ((double)size) / 2; |
| } |
| else { |
| //even |
| majority = ((double)size) / 2 + 1; |
| } |
| //votes needed could be say 2.5 so we add 1 in this case |
| votesNeeded = (int) majority; |
| latch = new CountDownLatch(votesNeeded); |
| if (votesNeeded == 0) { |
| decision = true; |
| } |
| } |
| |
| /** |
| * if we can connect to a node |
| * |
| * @return |
| */ |
| @Override |
| public Vote connected() { |
| return new BooleanVote(true); |
| } |
| |
| /** |
| * if we cant connect to the node |
| * |
| * @return |
| */ |
| @Override |
| public Vote notConnected() { |
| return new BooleanVote(false); |
| } |
| |
| /** |
| * live nodes | remaining nodes | majority | votes needed |
| * 1 | 0 | 0 | 0 |
| * 2 | 1 | 1 | 1 |
| * n | r = n-1 | n/2 + 1 | n/2 + 1 rounded |
| * 3 | 2 | 2.5 | 2 |
| * 4 | 3 | 3 | 3 |
| * 5 | 4 | 3.5 | 3 |
| * 6 | 5 | 4 | 4 |
| * |
| * @param vote the vote to make. |
| */ |
| @Override |
| public synchronized void vote(BooleanVote vote) { |
| if (decision) |
| return; |
| if (vote.getVote()) { |
| total++; |
| latch.countDown(); |
| if (total >= votesNeeded) { |
| decision = true; |
| } |
| } |
| } |
| |
| @Override |
| public void allVotesCast(Topology voteTopology) { |
| |
| } |
| |
| @Override |
| public Boolean getDecision() { |
| return decision; |
| } |
| |
| @Override |
| public SimpleString getName() { |
| return null; |
| } |
| |
| public void await(int latchTimeout, TimeUnit unit) throws InterruptedException { |
| latch.await(latchTimeout, unit); |
| } |
| } |