2 * Copyright (c) 2015 Cisco Systems, Inc. and others. All rights reserved.
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
9 package org.opendaylight.controller.cluster.datastore.entityownership.selectionstrategy;
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 edu.umd.cs.findbugs.annotations.SuppressFBWarnings;
16 import java.util.Collection;
17 import java.util.HashMap;
19 import javax.annotation.Nullable;
22 * The LeastLoadedCandidateSelectionStrategy assigns ownership for an entity to the candidate which owns the least
25 public class LeastLoadedCandidateSelectionStrategy extends AbstractEntityOwnerSelectionStrategy {
26 private final Map<String, Long> localStatistics = new HashMap<>();
28 protected LeastLoadedCandidateSelectionStrategy(long selectionDelayInMillis, Map<String, Long> initialStatistics) {
29 super(selectionDelayInMillis, initialStatistics);
31 localStatistics.putAll(initialStatistics);
35 @SuppressFBWarnings(value = "NP_PARAMETER_MUST_BE_NONNULL_BUT_MARKED_AS_NULLABLE",
36 justification = "Unrecognised NullableDecl")
37 public String newOwner(@Nullable String currentOwner, Collection<String> viableCandidates) {
38 Preconditions.checkArgument(viableCandidates.size() > 0);
39 String leastLoadedCandidate = null;
40 long leastLoadedCount = Long.MAX_VALUE;
42 if (!Strings.isNullOrEmpty(currentOwner)) {
43 long localVal = MoreObjects.firstNonNull(localStatistics.get(currentOwner), 0L);
44 localStatistics.put(currentOwner, localVal - 1);
47 for (String candidateName : viableCandidates) {
48 long val = MoreObjects.firstNonNull(localStatistics.get(candidateName), 0L);
49 if (val < leastLoadedCount) {
50 leastLoadedCount = val;
51 leastLoadedCandidate = candidateName;
55 if (leastLoadedCandidate == null) {
56 leastLoadedCandidate = viableCandidates.iterator().next();
59 localStatistics.put(leastLoadedCandidate, leastLoadedCount + 1);
60 return leastLoadedCandidate;
64 Map<String, Long> getLocalStatistics() {
65 return localStatistics;