org.elasticsearch.cluster.routing.allocation.allocator.ShardsAllocator Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of elasticsearch Show documentation
Show all versions of elasticsearch Show documentation
Elasticsearch subproject :server
/*
* 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.allocator;
import org.elasticsearch.cluster.node.DiscoveryNode;
import org.elasticsearch.cluster.routing.ShardRouting;
import org.elasticsearch.cluster.routing.allocation.RoutingAllocation;
import java.util.Map;
/**
*
* A {@link ShardsAllocator} is the main entry point for shard allocation on nodes in the cluster.
* The allocator makes basic decision where a shard instance will be allocated, if already allocated instances
* need to relocate to other nodes due to node failures or due to rebalancing decisions.
*
*/
public interface ShardsAllocator {
/**
* Allocates shards to nodes in the cluster. An implementation of this method should:
* - assign unassigned shards
* - relocate shards that cannot stay on a node anymore
* - relocate shards to find a good shard balance in the cluster
*
* @param allocation current node allocation
*/
void allocate(RoutingAllocation allocation);
/**
* Returns a map of node to a float "weight" of where the allocator would like to place the shard.
* Higher weights signify greater desire to place the shard on that node.
* Does not modify the allocation at all.
*
* @param allocation current node allocation
* @param shard shard to weigh
* @return map of nodes to float weights
*/
Map weighShard(RoutingAllocation allocation, ShardRouting shard);
}