001    /*
002     * CDDL HEADER START
003     *
004     * The contents of this file are subject to the terms of the
005     * Common Development and Distribution License, Version 1.0 only
006     * (the "License").  You may not use this file except in compliance
007     * with the License.
008     *
009     * You can obtain a copy of the license at
010     * trunk/opends/resource/legal-notices/OpenDS.LICENSE
011     * or https://OpenDS.dev.java.net/OpenDS.LICENSE.
012     * See the License for the specific language governing permissions
013     * and limitations under the License.
014     *
015     * When distributing Covered Code, include this CDDL HEADER in each
016     * file and include the License file at
017     * trunk/opends/resource/legal-notices/OpenDS.LICENSE.  If applicable,
018     * add the following below this CDDL HEADER, with the fields enclosed
019     * by brackets "[]" replaced with your own identifying information:
020     *      Portions Copyright [yyyy] [name of copyright owner]
021     *
022     * CDDL HEADER END
023     *
024     *
025     *      Copyright 2006-2008 Sun Microsystems, Inc.
026     */
027    package org.opends.server.replication.server;
028    
029    import java.util.LinkedList;
030    
031    import org.opends.server.replication.common.ChangeNumber;
032    
033    /**
034     * This class is used to store the list of acks received for
035     * a Given Update Messages.
036     *
037     * The acks are kept only for the update that are marked, hopefully this
038     * should be a limited number of updates and in all cases, LDAP servers
039     * operations are going to be blocked waiting for these acks so they
040     * won't be able to generate a huge number of such messages.
041     *
042     * Therefore, the amount of memory used keeping those changes is not a problem,
043     */
044    public class AckMessageList
045    {
046      // The ChangeNumber of the updates that was acked
047      // or that is waiting acks
048      private ChangeNumber changeNumber;
049    
050      // The list of serverIdentifiers for which acks have been received so far
051      // can be empty when no acks have been received
052      private LinkedList<Short> acks;
053    
054      private int numExpectedAcks;
055    
056      /**
057       * Creates a new AckMessageList for a given ChangeNumber.
058       *
059       * @param changeNumber The ChangeNumber for which the ack list is created.
060       * @param numExpectedAcks The number of acks waited before acking the
061       *                        original change.
062       */
063      public AckMessageList(ChangeNumber changeNumber, int numExpectedAcks)
064      {
065        acks = new LinkedList<Short>();
066        this.changeNumber = changeNumber;
067        this.numExpectedAcks = numExpectedAcks;
068      }
069    
070      /**
071       * Get the ChangeNumber of this Ack Message List.
072       * @return Returns the changeNumber.
073       */
074      public ChangeNumber getChangeNumber()
075      {
076        return changeNumber;
077      }
078    
079      /**
080       * Add an ack from a given LDAP server to the ack list.
081       *
082       * @param serverId the identifier of the LDAP server.
083       */
084      public synchronized void addAck(short serverId)
085      {
086        acks.add(serverId);
087      }
088    
089      /**
090       * This method can be used to check if all acks have been received for the
091       * ChangeNumber managed by this list.
092       * @return A boolean indicating if all acks have been received for the
093       *         ChangeNumber managed by this list.
094       */
095      public boolean completed()
096      {
097        return (acks.size() >= numExpectedAcks);
098      }
099    }