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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.routing.allocation.decider;
import org.elasticsearch.cluster.routing.RoutingNode;
import org.elasticsearch.cluster.routing.ShardRouting;
import org.elasticsearch.cluster.routing.allocation.RoutingAllocation;
import org.elasticsearch.common.Strings;
import org.elasticsearch.common.settings.Settings;
/**
* An allocation decider that prevents multiple instances of the same shard to
* be allocated on the same <tt>node</tt>.
*
* The {@value #SAME_HOST_SETTING} setting allows to perform a check to prevent
* allocation of multiple instances of the same shard on a single <tt>host</tt>,
* based on host name and host address. Defaults to `false`, meaning that no
* check is performed by default.
*
* <p>
* Note: this setting only applies if multiple nodes are started on the same
* <tt>host</tt>. Allocations of multiple copies of the same shard on the same
* <tt>node</tt> are not allowed independently of this setting.
* </p>
*/
public class SameShardAllocationDecider extends AllocationDecider {
public static final String NAME = "same_shard";
public static final String SAME_HOST_SETTING = "cluster.routing.allocation.same_shard.host";
private final boolean sameHost;
public SameShardAllocationDecider(Settings settings) {
super(settings);
this.sameHost = settings.getAsBoolean(SAME_HOST_SETTING, false);
}
@Override
public Decision canAllocate(ShardRouting shardRouting, RoutingNode node, RoutingAllocation allocation) {
Iterable<ShardRouting> assignedShards = allocation.routingNodes().assignedShards(shardRouting.shardId());
for (ShardRouting assignedShard : assignedShards) {
if (node.nodeId().equals(assignedShard.currentNodeId())) {
return allocation.decision(Decision.NO, NAME,
"the shard cannot be allocated on the same node id [%s] on which it already exists", node.nodeId());
}
}
if (sameHost) {
if (node.node() != null) {
for (RoutingNode checkNode : allocation.routingNodes()) {
if (checkNode.node() == null) {
continue;
}
// check if its on the same host as the one we want to allocate to
boolean checkNodeOnSameHost = false;
if (Strings.hasLength(checkNode.node().getHostAddress()) && Strings.hasLength(node.node().getHostAddress())) {
if (checkNode.node().getHostAddress().equals(node.node().getHostAddress())) {
checkNodeOnSameHost = true;
}
} else if (Strings.hasLength(checkNode.node().getHostName()) && Strings.hasLength(node.node().getHostName())) {
if (checkNode.node().getHostName().equals(node.node().getHostName())) {
checkNodeOnSameHost = true;
}
}
if (checkNodeOnSameHost) {
for (ShardRouting assignedShard : assignedShards) {
if (checkNode.nodeId().equals(assignedShard.currentNodeId())) {
return allocation.decision(Decision.NO, NAME,
"shard cannot be allocated on the same host [%s] on which it already exists", node.nodeId());
}
}
}
}
}
}
return allocation.decision(Decision.YES, NAME, "shard is not allocated to same node or host");
}
}
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