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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;
import org.elasticsearch.cluster.routing.allocation.decider.Decision;
import org.elasticsearch.cluster.routing.allocation.decider.Decision.Type;
import org.elasticsearch.common.Nullable;
import java.util.Collections;
import java.util.Map;
/**
* Represents a decision to move a started shard to form a more optimally balanced cluster.
*/
public final class RebalanceDecision extends RelocationDecision {
/** a constant representing no decision taken */
public static final RebalanceDecision NOT_TAKEN = new RebalanceDecision(null, null, null, null, null, Float.POSITIVE_INFINITY);
@Nullable
private final Decision canRebalanceDecision;
@Nullable
private final Map nodeDecisions;
private float currentWeight;
public RebalanceDecision(Decision canRebalanceDecision, Type finalDecision, String finalExplanation) {
this(canRebalanceDecision, finalDecision, finalExplanation, null, null, Float.POSITIVE_INFINITY);
}
public RebalanceDecision(Decision canRebalanceDecision, Type finalDecision, String finalExplanation,
String assignedNodeId, Map nodeDecisions, float currentWeight) {
super(finalDecision, finalExplanation, assignedNodeId);
this.canRebalanceDecision = canRebalanceDecision;
this.nodeDecisions = nodeDecisions != null ? Collections.unmodifiableMap(nodeDecisions) : null;
this.currentWeight = currentWeight;
}
/**
* Creates a new {@link RebalanceDecision}, computing the explanation based on the decision parameters.
*/
public static RebalanceDecision decision(Decision canRebalanceDecision, Type finalDecision, String assignedNodeId,
Map nodeDecisions, float currentWeight, float threshold) {
final String explanation = produceFinalExplanation(finalDecision, assignedNodeId, threshold);
return new RebalanceDecision(canRebalanceDecision, finalDecision, explanation, assignedNodeId, nodeDecisions, currentWeight);
}
/**
* Returns the decision for being allowed to rebalance the shard.
*/
@Nullable
public Decision getCanRebalanceDecision() {
return canRebalanceDecision;
}
/**
* Gets the individual node-level decisions that went into making the final decision as represented by
* {@link #getFinalDecisionType()}. The map that is returned has the node id as the key and a {@link NodeRebalanceResult}.
*/
@Nullable
public Map getNodeDecisions() {
return nodeDecisions;
}
private static String produceFinalExplanation(final Type finalDecisionType, final String assignedNodeId, final float threshold) {
final String finalExplanation;
if (assignedNodeId != null) {
if (finalDecisionType == Type.THROTTLE) {
finalExplanation = "throttle moving shard to node [" + assignedNodeId + "], as it is " +
"currently busy with other shard relocations";
} else {
finalExplanation = "moving shard to node [" + assignedNodeId + "] to form a more balanced cluster";
}
} else {
finalExplanation = "cannot rebalance shard, no other node exists that would form a more balanced " +
"cluster within the defined threshold [" + threshold + "]";
}
return finalExplanation;
}
}