/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License, Version 1.0 only
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* (the "License"). You may not use this file except in compliance
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* with the License.
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*
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* You can obtain a copy of the license at legal-notices/CDDLv1_0.txt
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* or http://forgerock.org/license/CDDLv1.0.html.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at legal-notices/CDDLv1_0.txt.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information:
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* Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*
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*
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* Copyright 2013-2014 ForgeRock AS
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*/
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package org.opends.server.replication.server.changelog.je;
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import java.util.*;
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import java.util.Map.Entry;
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import org.opends.server.replication.common.CSN;
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import org.opends.server.replication.protocol.UpdateMsg;
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import org.opends.server.replication.server.changelog.api.ChangelogException;
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import org.opends.server.replication.server.changelog.api.DBCursor;
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import org.opends.server.util.StaticUtils;
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/**
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* {@link DBCursor} implementation that iterates across a Collection of
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* {@link DBCursor}s, advancing from the oldest to the newest change cross all
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* cursors.
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*
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* @param <Data>
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* The type of data associated with each cursor
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*/
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public final class CompositeDBCursor<Data> implements DBCursor<UpdateMsg>
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{
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private static final byte UNINITIALIZED = 0;
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private static final byte READY = 1;
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private static final byte CLOSED = 2;
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/**
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* The state of this cursor. One of {@link #UNINITIALIZED}, {@link #READY} or
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* {@link #CLOSED}
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*/
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private byte state = UNINITIALIZED;
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/** Whether this composite should try to recycle exhausted cursors. */
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private final boolean recycleExhaustedCursors;
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/**
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* These cursors are considered exhausted because they had no new changes the
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* last time {@link DBCursor#next()} was called on them. Exhausted cursors
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* might be recycled at some point when they start returning changes again.
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*/
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private final Map<DBCursor<UpdateMsg>, Data> exhaustedCursors =
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new HashMap<DBCursor<UpdateMsg>, Data>();
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/**
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* The cursors are sorted based on the current change of each cursor to
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* consider the next change across all available cursors.
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*/
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private final NavigableMap<DBCursor<UpdateMsg>, Data> cursors =
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new TreeMap<DBCursor<UpdateMsg>, Data>(
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new Comparator<DBCursor<UpdateMsg>>()
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{
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@Override
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public int compare(DBCursor<UpdateMsg> o1, DBCursor<UpdateMsg> o2)
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{
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final CSN csn1 = o1.getRecord().getCSN();
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final CSN csn2 = o2.getRecord().getCSN();
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return CSN.compare(csn1, csn2);
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}
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});
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/**
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* Builds a CompositeDBCursor using the provided collection of cursors.
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*
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* @param cursors
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* the cursors that will be iterated upon.
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* @param recycleExhaustedCursors
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* whether a call to {@link #next()} tries to recycle exhausted
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* cursors
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*/
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public CompositeDBCursor(Map<DBCursor<UpdateMsg>, Data> cursors,
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boolean recycleExhaustedCursors)
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{
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this.recycleExhaustedCursors = recycleExhaustedCursors;
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for (Entry<DBCursor<UpdateMsg>, Data> entry : cursors.entrySet())
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{
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put(entry);
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}
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}
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/** {@inheritDoc} */
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@Override
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public boolean next() throws ChangelogException
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{
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if (state == CLOSED)
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{
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return false;
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}
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final boolean advanceNonExhaustedCursors = state != UNINITIALIZED;
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state = READY;
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if (recycleExhaustedCursors && !exhaustedCursors.isEmpty())
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{
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// try to recycle empty cursors in case the underlying ReplicaDBs received
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// new changes.
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final Map<DBCursor<UpdateMsg>, Data> copy =
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new HashMap<DBCursor<UpdateMsg>, Data>(exhaustedCursors);
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exhaustedCursors.clear();
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for (Entry<DBCursor<UpdateMsg>, Data> entry : copy.entrySet())
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{
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entry.getKey().next();
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put(entry);
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}
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final Entry<DBCursor<UpdateMsg>, Data> firstEntry = cursors.firstEntry();
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if (firstEntry != null && copy.containsKey(firstEntry.getKey()))
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{
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// if the first cursor was previously an exhausted cursor,
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// then we have already called next() on it.
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// Avoid calling it again because we know new changes have been found.
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return true;
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}
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}
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// To keep consistent the cursors' order in the SortedSet, it is necessary
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// to remove and add again the cursor after moving it forward.
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if (advanceNonExhaustedCursors)
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{
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Entry<DBCursor<UpdateMsg>, Data> firstEntry = cursors.pollFirstEntry();
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if (firstEntry != null)
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{
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final DBCursor<UpdateMsg> cursor = firstEntry.getKey();
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cursor.next();
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put(firstEntry);
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}
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}
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// no cursors are left with changes.
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return !cursors.isEmpty();
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}
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private void put(Entry<DBCursor<UpdateMsg>, Data> entry)
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{
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final DBCursor<UpdateMsg> cursor = entry.getKey();
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final Data data = entry.getValue();
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if (cursor.getRecord() != null)
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{
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this.cursors.put(cursor, data);
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}
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else
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{
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this.exhaustedCursors.put(cursor, data);
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}
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}
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/** {@inheritDoc} */
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@Override
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public UpdateMsg getRecord()
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{
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final Entry<DBCursor<UpdateMsg>, Data> entry = cursors.firstEntry();
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if (entry != null)
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{
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return entry.getKey().getRecord();
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}
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return null;
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}
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/**
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* Returns the data associated to the cursor that returned the current record.
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*
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* @return the data associated to the cursor that returned the current record.
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*/
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public Data getData()
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{
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final Entry<DBCursor<UpdateMsg>, Data> entry = cursors.firstEntry();
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if (entry != null)
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{
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return entry.getValue();
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}
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return null;
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}
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/** {@inheritDoc} */
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@Override
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public void close()
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{
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StaticUtils.close(cursors.keySet());
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StaticUtils.close(exhaustedCursors.keySet());
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}
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/** {@inheritDoc} */
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@Override
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public String toString()
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{
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return getClass().getSimpleName() + " openCursors=" + cursors
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+ " exhaustedCursors=" + exhaustedCursors;
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}
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}
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