Bump odlparent to 3.1.2
[controller.git] / opendaylight / md-sal / sal-distributed-datastore / src / main / java / org / opendaylight / controller / cluster / datastore / entityownership / selectionstrategy / LeastLoadedCandidateSelectionStrategy.java
1 /*
2  * Copyright (c) 2015 Cisco Systems, Inc. and others.  All rights reserved.
3  *
4  * This program and the accompanying materials are made available under the
5  * terms of the Eclipse Public License v1.0 which accompanies this distribution,
6  * and is available at http://www.eclipse.org/legal/epl-v10.html
7  */
8
9 package org.opendaylight.controller.cluster.datastore.entityownership.selectionstrategy;
10
11 import com.google.common.annotations.VisibleForTesting;
12 import com.google.common.base.MoreObjects;
13 import com.google.common.base.Preconditions;
14 import com.google.common.base.Strings;
15 import java.util.Collection;
16 import java.util.HashMap;
17 import java.util.Map;
18 import javax.annotation.Nullable;
19
20 /**
21  * The LeastLoadedCandidateSelectionStrategy assigns ownership for an entity to the candidate which owns the least
22  * number of entities.
23  */
24 public class LeastLoadedCandidateSelectionStrategy extends AbstractEntityOwnerSelectionStrategy {
25     private final Map<String, Long> localStatistics = new HashMap<>();
26
27     protected LeastLoadedCandidateSelectionStrategy(long selectionDelayInMillis, Map<String, Long> initialStatistics) {
28         super(selectionDelayInMillis, initialStatistics);
29
30         localStatistics.putAll(initialStatistics);
31     }
32
33     @Override
34     public String newOwner(@Nullable String currentOwner, Collection<String> viableCandidates) {
35         Preconditions.checkArgument(viableCandidates.size() > 0);
36         String leastLoadedCandidate = null;
37         long leastLoadedCount = Long.MAX_VALUE;
38
39         if (!Strings.isNullOrEmpty(currentOwner)) {
40             long localVal = MoreObjects.firstNonNull(localStatistics.get(currentOwner), 0L);
41             localStatistics.put(currentOwner, localVal - 1);
42         }
43
44         for (String candidateName : viableCandidates) {
45             long val = MoreObjects.firstNonNull(localStatistics.get(candidateName), 0L);
46             if (val < leastLoadedCount) {
47                 leastLoadedCount = val;
48                 leastLoadedCandidate = candidateName;
49             }
50         }
51
52         if (leastLoadedCandidate == null) {
53             leastLoadedCandidate = viableCandidates.iterator().next();
54         }
55
56         localStatistics.put(leastLoadedCandidate, leastLoadedCount + 1);
57         return leastLoadedCandidate;
58     }
59
60     @VisibleForTesting
61     Map<String, Long> getLocalStatistics() {
62         return localStatistics;
63     }
64 }

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