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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.ShardRouting;
import org.elasticsearch.cluster.routing.allocation.RoutingAllocation;
import org.elasticsearch.common.inject.Inject;
import org.elasticsearch.common.settings.ClusterSettings;
import org.elasticsearch.common.settings.Setting;
import org.elasticsearch.common.settings.Setting.Property;
import org.elasticsearch.common.settings.Settings;
/**
* Similar to the {@link ClusterRebalanceAllocationDecider} this
* {@link AllocationDecider} controls the number of currently in-progress
* re-balance (relocation) operations and restricts node allocations if the
* configured threshold is reached. The default number of concurrent rebalance
* operations is set to <tt>2</tt>
* <p>
* Re-balance operations can be controlled in real-time via the cluster update API using
* <tt>cluster.routing.allocation.cluster_concurrent_rebalance</tt>. Iff this
* setting is set to <tt>-1</tt> the number of concurrent re-balance operations
* are unlimited.
*/
public class ConcurrentRebalanceAllocationDecider extends AllocationDecider {
public static final String NAME = "concurrent_rebalance";
public static final Setting<Integer> CLUSTER_ROUTING_ALLOCATION_CLUSTER_CONCURRENT_REBALANCE_SETTING =
Setting.intSetting("cluster.routing.allocation.cluster_concurrent_rebalance", 2, -1,
Property.Dynamic, Property.NodeScope);
private volatile int clusterConcurrentRebalance;
@Inject
public ConcurrentRebalanceAllocationDecider(Settings settings, ClusterSettings clusterSettings) {
super(settings);
this.clusterConcurrentRebalance = CLUSTER_ROUTING_ALLOCATION_CLUSTER_CONCURRENT_REBALANCE_SETTING.get(settings);
logger.debug("using [cluster_concurrent_rebalance] with [{}]", clusterConcurrentRebalance);
clusterSettings.addSettingsUpdateConsumer(CLUSTER_ROUTING_ALLOCATION_CLUSTER_CONCURRENT_REBALANCE_SETTING,
this::setClusterConcurrentRebalance);
}
private void setClusterConcurrentRebalance(int concurrentRebalance) {
clusterConcurrentRebalance = concurrentRebalance;
}
@Override
public Decision canRebalance(ShardRouting shardRouting, RoutingAllocation allocation) {
if (clusterConcurrentRebalance == -1) {
return allocation.decision(Decision.YES, NAME, "unlimited concurrent rebalances are allowed");
}
int relocatingShards = allocation.routingNodes().getRelocatingShardCount();
if (relocatingShards >= clusterConcurrentRebalance) {
return allocation.decision(Decision.NO, NAME,
"too many shards are concurrently rebalancing [%d], limit: [%d]",
relocatingShards, clusterConcurrentRebalance);
}
return allocation.decision(Decision.YES, NAME,
"below threshold [%d] for concurrent rebalances, current rebalance shard count [%d]",
clusterConcurrentRebalance, relocatingShards);
}
}
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