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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.gateway;
import org.apache.logging.log4j.Logger;
import org.elasticsearch.cluster.routing.RoutingNode;
import org.elasticsearch.cluster.routing.RoutingNodes;
import org.elasticsearch.cluster.routing.ShardRouting;
import org.elasticsearch.cluster.routing.allocation.AllocateUnassignedDecision;
import org.elasticsearch.cluster.routing.allocation.AllocationDecision;
import org.elasticsearch.cluster.routing.allocation.NodeAllocationResult;
import org.elasticsearch.cluster.routing.allocation.RoutingAllocation;
import org.elasticsearch.cluster.routing.allocation.decider.Decision;
import org.elasticsearch.common.component.AbstractComponent;
import org.elasticsearch.common.settings.Settings;
import java.util.ArrayList;
import java.util.List;
/**
* An abstract class that implements basic functionality for allocating
* shards to nodes based on shard copies that already exist in the cluster.
*
* Individual implementations of this class are responsible for providing
* the logic to determine to which nodes (if any) those shards are allocated.
*/
public abstract class BaseGatewayShardAllocator extends AbstractComponent {
public BaseGatewayShardAllocator(Settings settings) {
super(settings);
}
/**
* Allocate unassigned shards to nodes (if any) where valid copies of the shard already exist.
* It is up to the individual implementations of {@link #makeAllocationDecision(ShardRouting, RoutingAllocation, Logger)}
* to make decisions on assigning shards to nodes.
*
* @param allocation the allocation state container object
*/
public void allocateUnassigned(RoutingAllocation allocation) {
final RoutingNodes routingNodes = allocation.routingNodes();
final RoutingNodes.UnassignedShards.UnassignedIterator unassignedIterator = routingNodes.unassigned().iterator();
while (unassignedIterator.hasNext()) {
final ShardRouting shard = unassignedIterator.next();
final AllocateUnassignedDecision allocateUnassignedDecision = makeAllocationDecision(shard, allocation, logger);
if (allocateUnassignedDecision.isDecisionTaken() == false) {
// no decision was taken by this allocator
continue;
}
if (allocateUnassignedDecision.getAllocationDecision() == AllocationDecision.YES) {
unassignedIterator.initialize(allocateUnassignedDecision.getTargetNode().getId(),
allocateUnassignedDecision.getAllocationId(),
shard.primary() ? ShardRouting.UNAVAILABLE_EXPECTED_SHARD_SIZE :
allocation.clusterInfo().getShardSize(shard, ShardRouting.UNAVAILABLE_EXPECTED_SHARD_SIZE),
allocation.changes());
} else {
unassignedIterator.removeAndIgnore(allocateUnassignedDecision.getAllocationStatus(), allocation.changes());
}
}
}
/**
* Make a decision on the allocation of an unassigned shard. This method is used by
* {@link #allocateUnassigned(RoutingAllocation)} to make decisions about whether or not
* the shard can be allocated by this allocator and if so, to which node it will be allocated.
*
* @param unassignedShard the unassigned shard to allocate
* @param allocation the current routing state
* @param logger the logger
* @return an {@link AllocateUnassignedDecision} with the final decision of whether to allocate and details of the decision
*/
public abstract AllocateUnassignedDecision makeAllocationDecision(ShardRouting unassignedShard,
RoutingAllocation allocation,
Logger logger);
/**
* Builds decisions for all nodes in the cluster, so that the explain API can provide information on
* allocation decisions for each node, while still waiting to allocate the shard (e.g. due to fetching shard data).
*/
protected List<NodeAllocationResult> buildDecisionsForAllNodes(ShardRouting shard, RoutingAllocation allocation) {
List<NodeAllocationResult> results = new ArrayList<>();
for (RoutingNode node : allocation.routingNodes()) {
Decision decision = allocation.deciders().canAllocate(shard, node, allocation);
results.add(new NodeAllocationResult(node.node(), null, decision));
}
return results;
}
}