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.base.MoreObjects;
  12 import java.util.Collection;
  13 import java.util.HashMap;
  14 import java.util.Map;
  15 import org.slf4j.Logger;
  16 import org.slf4j.LoggerFactory;
  17
  18 /**
  19  * The LeastLoadedCandidateSelectionStrategy assigns ownership for an entity to the candidate which owns the least
  20  * number of entities.
  21  */
  22 public class LeastLoadedCandidateSelectionStrategy extends AbstractEntityOwnerSelectionStrategy {
  23     private static final Logger LOG = LoggerFactory.getLogger(LeastLoadedCandidateSelectionStrategy.class);
  24
  25     private Map<String, Long> localStatistics = new HashMap<>();
  26
  27     protected LeastLoadedCandidateSelectionStrategy(long selectionDelayInMillis) {
  28         super(selectionDelayInMillis);
  29     }
  30
  31     @Override
  32     public String newOwner(Collection<String> viableCandidates, Map<String, Long> statistics) {
  33         String leastLoadedCandidate = null;
  34         long leastLoadedCount = Long.MAX_VALUE;
  35
  36         for(String candidateName : viableCandidates){
  37             long val = MoreObjects.firstNonNull(statistics.get(candidateName), 0L);
  38             long localVal = MoreObjects.firstNonNull(localStatistics.get(candidateName), 0L);
  39             if(val < localVal){
  40                 LOG.debug("Local statistic higher - Candidate : {}, local statistic : {}, provided statistic : {}",
  41                         candidateName, localVal, val);
  42                 val = localVal;
  43             } else {
  44                 LOG.debug("Provided statistic higher - Candidate : {}, local statistic : {}, provided statistic : {}",
  45                         candidateName, localVal, val);
  46                 localStatistics.put(candidateName, val);
  47             }
  48             if(val < leastLoadedCount){
  49                 leastLoadedCount = val;
  50                 leastLoadedCandidate = candidateName;
  51             }
  52         }
  53
  54         if(leastLoadedCandidate == null){
  55             leastLoadedCandidate = viableCandidates.iterator().next();
  56         }
  57
  58         localStatistics.put(leastLoadedCandidate, leastLoadedCount + 1);
  59         return leastLoadedCandidate;
  60     }
  61 }