/*
* Licensed to Elastic Search and Shay Banon under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. Elastic Search 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.discovery.zen.elect;
import org.elasticsearch.cluster.node.DiscoveryNode;
import org.elasticsearch.common.collect.Lists;
import org.elasticsearch.common.component.AbstractComponent;
import org.elasticsearch.common.settings.Settings;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
/**
* @author kimchy (shay.banon)
*/
public class ElectMasterService extends AbstractComponent {
private final NodeComparator nodeComparator = new NodeComparator();
private final int minimumMasterNodes;
public ElectMasterService(Settings settings) {
super(settings);
this.minimumMasterNodes = settings.getAsInt("discovery.zen.minimum_master_nodes", -1);
}
public boolean hasEnoughMasterNodes(Iterable<DiscoveryNode> nodes) {
if (minimumMasterNodes < 1) {
return true;
}
int count = 0;
for (DiscoveryNode node : nodes) {
if (node.masterNode()) {
count++;
}
}
return count >= minimumMasterNodes;
}
/**
* Returns a list of the next possible masters.
*/
public DiscoveryNode[] nextPossibleMasters(Iterable<DiscoveryNode> nodes, int numberOfPossibleMasters) {
List<DiscoveryNode> sortedNodes = sortedMasterNodes(nodes);
if (sortedNodes == null) {
return new DiscoveryNode[0];
}
List<DiscoveryNode> nextPossibleMasters = Lists.newArrayListWithCapacity(numberOfPossibleMasters);
int counter = 0;
for (DiscoveryNode nextPossibleMaster : sortedNodes) {
if (++counter >= numberOfPossibleMasters) {
break;
}
nextPossibleMasters.add(nextPossibleMaster);
}
return nextPossibleMasters.toArray(new DiscoveryNode[nextPossibleMasters.size()]);
}
/**
* Elects a new master out of the possible nodes, returning it. Returns <tt>null</tt>
* if no master has been elected.
*/
public DiscoveryNode electMaster(Iterable<DiscoveryNode> nodes) {
List<DiscoveryNode> sortedNodes = sortedMasterNodes(nodes);
if (sortedNodes == null || sortedNodes.isEmpty()) {
return null;
}
return sortedNodes.get(0);
}
private List<DiscoveryNode> sortedMasterNodes(Iterable<DiscoveryNode> nodes) {
List<DiscoveryNode> possibleNodes = Lists.newArrayList(nodes);
if (possibleNodes.isEmpty()) {
return null;
}
// clean non master nodes
for (Iterator<DiscoveryNode> it = possibleNodes.iterator(); it.hasNext(); ) {
DiscoveryNode node = it.next();
if (!node.masterNode()) {
it.remove();
}
}
Collections.sort(possibleNodes, nodeComparator);
return possibleNodes;
}
private static class NodeComparator implements Comparator<DiscoveryNode> {
@Override public int compare(DiscoveryNode o1, DiscoveryNode o2) {
return o1.id().compareTo(o2.id());
}
}
}