/*
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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 2006-2009 Sun Microsystems, Inc.
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* Portions Copyright 2011-2014 ForgeRock AS
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*/
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package org.opends.server.replication.server.changelog.je;
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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.replication.server.changelog.je.ReplicationDB.ReplServerDBCursor;
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import static org.opends.server.replication.server.changelog.api.DBCursor.KeyMatchingStrategy.*;
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import static org.opends.server.replication.server.changelog.api.DBCursor.PositionStrategy.*;
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/**
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* Berkeley DB JE implementation of {@link DBCursor}.
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*
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* \@NotThreadSafe
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*/
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class JEReplicaDBCursor implements DBCursor<UpdateMsg>
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{
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private final ReplicationDB db;
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private PositionStrategy positionStrategy;
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private KeyMatchingStrategy matchingStrategy;
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private JEReplicaDB replicaDB;
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private final CSN startCSN;
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private CSN lastNonNullCurrentCSN;
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/**
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* The underlying replica DB cursor.
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* <p>
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* Initially <code>null</code>, the first call to {@link #next()} will
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* populate it. A call to {@link #close()} will set it to null again.
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*/
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private ReplServerDBCursor cursor;
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/**
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* Creates a new {@link JEReplicaDBCursor}. All created cursor must be
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* released by the caller using the {@link #close()} method.
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*
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* @param db
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* The db where the cursor must be created.
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* @param startCSN
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* The CSN after which the cursor must start.If null, start from the
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* oldest CSN
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* @param matchingStrategy
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* Cursor key matching strategy
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* @param positionStrategy
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* Cursor position strategy
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* @param replicaDB
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* The associated JEReplicaDB.
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* @throws ChangelogException
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* if a database problem happened.
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*/
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public JEReplicaDBCursor(ReplicationDB db, CSN startCSN, KeyMatchingStrategy matchingStrategy,
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PositionStrategy positionStrategy, JEReplicaDB replicaDB) throws ChangelogException
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{
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this.db = db;
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this.matchingStrategy = matchingStrategy;
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this.positionStrategy = positionStrategy;
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this.replicaDB = replicaDB;
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this.startCSN = startCSN;
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this.lastNonNullCurrentCSN = startCSN;
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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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if (!isClosed() && cursor != null)
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{
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return cursor.getRecord();
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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 boolean next() throws ChangelogException
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{
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if (isClosed())
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{
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return false;
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}
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final ReplServerDBCursor previousCursor = cursor;
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if (getRecord() == null)
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{
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synchronized (this)
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{
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closeCursor();
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// Previously exhausted cursor must be able to reinitialize themselves.
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// There is a risk of readLock never being unlocked
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// if following code is called while the cursor is closed.
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// It is better to let the deadlock happen to help quickly identifying
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// and fixing such issue with unit tests.
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if (lastNonNullCurrentCSN != startCSN)
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{
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// re-initialize to further CSN, take care to use appropriate strategies
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matchingStrategy = GREATER_THAN_OR_EQUAL_TO_KEY;
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positionStrategy = AFTER_MATCHING_KEY;
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}
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cursor = db.openReadCursor(lastNonNullCurrentCSN, matchingStrategy, positionStrategy);
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}
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}
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// For ON_MATCHING_KEY, do not call next() if the cursor has just been initialized.
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if (positionStrategy == ON_MATCHING_KEY && previousCursor != null
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|| positionStrategy == AFTER_MATCHING_KEY)
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{
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cursor.next();
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}
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final UpdateMsg currentRecord = cursor.getRecord();
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if (currentRecord != null)
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{
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lastNonNullCurrentCSN = currentRecord.getCSN();
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return true;
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}
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return false;
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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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synchronized (this)
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{
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closeCursor();
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replicaDB = null;
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}
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}
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private boolean isClosed()
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{
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return replicaDB == null;
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}
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private void closeCursor()
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{
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if (cursor != null)
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{
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cursor.close();
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cursor = null;
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}
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}
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/**
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* Called by the GC when the object is garbage collected. Release the internal
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* cursor in case the cursor was badly used and {@link #close()} was never
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* called.
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*/
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@Override
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protected void finalize()
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{
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close();
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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()
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+ " currentChange=" + cursor.getRecord()
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+ " positionStrategy=" + positionStrategy
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+ " matchingStrategy=" + matchingStrategy
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+ " replicaDB=" + replicaDB;
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}
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}
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