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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.metadata.IndexMetaData;
import org.elasticsearch.cluster.routing.MutableShardRouting;
import org.elasticsearch.cluster.routing.RoutingNode;
import org.elasticsearch.cluster.routing.ShardRouting;
import org.elasticsearch.cluster.routing.ShardRoutingState;
import org.elasticsearch.cluster.routing.allocation.RoutingAllocation;
import org.elasticsearch.common.inject.Inject;
import org.elasticsearch.common.settings.Settings;
/**
* This {@link AllocationDecider} limits the number of shards per node on a per
* index basis. The allocator prevents a single node to hold more than
* {@value #INDEX_TOTAL_SHARDS_PER_NODE} per index during the allocation
* process. The limits of this decider can be changed in real-time via a the
* index settings API.
* <p>
* If {@value #INDEX_TOTAL_SHARDS_PER_NODE} is reset to a negative value shards
* per index are unlimited per node. Shards currently in the
* {@link ShardRoutingState#RELOCATING relocating} state are ignored by this
* {@link AllocationDecider} until the shard changed its state to either
* {@link ShardRoutingState#STARTED started},
* {@link ShardRoutingState#INITIALIZING inializing} or
* {@link ShardRoutingState#UNASSIGNED unassigned}
* <p>
* Note: Reducing the number of shards per node via the index update API can
* trigger relocation and significant additional load on the clusters nodes.
* </p>
*/
public class ShardsLimitAllocationDecider extends AllocationDecider {
public static final String NAME = "shards_limit";
/**
* Controls the maximum number of shards per index on a single Elasticsearch
* node. Negative values are interpreted as unlimited.
*/
public static final String INDEX_TOTAL_SHARDS_PER_NODE = "index.routing.allocation.total_shards_per_node";
@Inject
public ShardsLimitAllocationDecider(Settings settings) {
super(settings);
}
@Override
public Decision canAllocate(ShardRouting shardRouting, RoutingNode node, RoutingAllocation allocation) {
IndexMetaData indexMd = allocation.routingNodes().metaData().index(shardRouting.index());
int totalShardsPerNode = indexMd.settings().getAsInt(INDEX_TOTAL_SHARDS_PER_NODE, -1);
if (totalShardsPerNode <= 0) {
return allocation.decision(Decision.YES, NAME, "total shard limit disabled: [%d] <= 0", totalShardsPerNode);
}
int nodeCount = 0;
for (MutableShardRouting nodeShard : node) {
if (!nodeShard.index().equals(shardRouting.index())) {
continue;
}
// don't count relocating shards...
if (nodeShard.relocating()) {
continue;
}
nodeCount++;
}
if (nodeCount >= totalShardsPerNode) {
return allocation.decision(Decision.NO, NAME, "too many shards for this index on node [%d], limit: [%d]",
nodeCount, totalShardsPerNode);
}
return allocation.decision(Decision.YES, NAME, "shard count under limit [%d] of total shards per node", totalShardsPerNode);
}
@Override
public Decision canRemain(ShardRouting shardRouting, RoutingNode node, RoutingAllocation allocation) {
IndexMetaData indexMd = allocation.routingNodes().metaData().index(shardRouting.index());
int totalShardsPerNode = indexMd.settings().getAsInt(INDEX_TOTAL_SHARDS_PER_NODE, -1);
if (totalShardsPerNode <= 0) {
return allocation.decision(Decision.YES, NAME, "total shard limit disabled: [%d] <= 0", totalShardsPerNode);
}
int nodeCount = 0;
for (MutableShardRouting nodeShard : node) {
if (!nodeShard.index().equals(shardRouting.index())) {
continue;
}
// don't count relocating shards...
if (nodeShard.relocating()) {
continue;
}
nodeCount++;
}
if (nodeCount > totalShardsPerNode) {
return allocation.decision(Decision.NO, NAME, "too many shards for this index on node [%d], limit: [%d]",
nodeCount, totalShardsPerNode);
}
return allocation.decision(Decision.YES, NAME, "shard count under limit [%d] of total shards per node", totalShardsPerNode);
}
}