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 org.slf4j.Logger;
  19 import org.slf4j.LoggerFactory;
  20
  21 /**
  22  * The LeastLoadedCandidateSelectionStrategy assigns ownership for an entity to the candidate which owns the least
  23  * number of entities.
  24  */
  25 public class LeastLoadedCandidateSelectionStrategy extends AbstractEntityOwnerSelectionStrategy {
  26     private static final Logger LOG = LoggerFactory.getLogger(LeastLoadedCandidateSelectionStrategy.class);
  27
  28     private Map<String, Long> localStatistics = new HashMap<>();
  29
  30     protected LeastLoadedCandidateSelectionStrategy(long selectionDelayInMillis, Map<String, Long> initialStatistics) {
  31         super(selectionDelayInMillis, initialStatistics);
  32
  33         localStatistics.putAll(initialStatistics);
  34     }
  35
  36     @Override
  37     public String newOwner(String currentOwner, Collection<String> viableCandidates) {
  38         Preconditions.checkArgument(viableCandidates.size() > 0);
  39         String leastLoadedCandidate = null;
  40         long leastLoadedCount = Long.MAX_VALUE;
  41
  42         if(!Strings.isNullOrEmpty(currentOwner)){
  43             long localVal = MoreObjects.firstNonNull(localStatistics.get(currentOwner), 0L);
  44             localStatistics.put(currentOwner, localVal - 1);
  45         }
  46
  47         for(String candidateName : viableCandidates){
  48             long val = MoreObjects.firstNonNull(localStatistics.get(candidateName), 0L);
  49             if(val < leastLoadedCount){
  50                 leastLoadedCount = val;
  51                 leastLoadedCandidate = candidateName;
  52             }
  53         }
  54
  55         if(leastLoadedCandidate == null){
  56             leastLoadedCandidate = viableCandidates.iterator().next();
  57         }
  58
  59         localStatistics.put(leastLoadedCandidate, leastLoadedCount + 1);
  60         return leastLoadedCandidate;
  61     }
  62
  63     @VisibleForTesting
  64     Map<String, Long> getLocalStatistics(){
  65         return localStatistics;
  66     }
  67 }