/*
* CDDL HEADER START
*
* The contents of this file are subject to the terms of the
* Common Development and Distribution License, Version 1.0 only
* (the "License"). You may not use this file except in compliance
* with the License.
*
* You can obtain a copy of the license at legal-notices/CDDLv1_0.txt
* or http://forgerock.org/license/CDDLv1.0.html.
* See the License for the specific language governing permissions
* and limitations under the License.
*
* When distributing Covered Code, include this CDDL HEADER in each
* file and include the License file at legal-notices/CDDLv1_0.txt.
* If applicable, add the following below this CDDL HEADER, with the
* fields enclosed by brackets "[]" replaced with your own identifying
* information:
* Portions Copyright [yyyy] [name of copyright owner]
*
* CDDL HEADER END
*
*
* Copyright 2014 ForgeRock AS.
*/
package org.opends.server.replication.server.changelog.file;
import static org.opends.server.replication.server.changelog.api.DBCursor.KeyMatchingStrategy.*;
import static org.opends.server.replication.server.changelog.api.DBCursor.PositionStrategy.*;
import org.opends.server.replication.common.CSN;
import org.opends.server.replication.protocol.UpdateMsg;
import org.opends.server.replication.server.changelog.api.ChangelogException;
import org.opends.server.replication.server.changelog.api.DBCursor;
import org.opends.server.replication.server.changelog.file.Log.RepositionableCursor;
/**
* A cursor on ReplicaDB, which can re-initialize itself after exhaustion.
* <p>
* The cursor provides a java.sql.ResultSet like API :
* <pre>
* FileReplicaDBCursor cursor = ...;
* try {
* while (cursor.next()) {
* Record record = cursor.getRecord();
* // ... can call cursor.getRecord() again: it will return the same result
* }
* }
* finally {
* close(cursor);
* }
* }
* </pre>
* <p>
* The cursor automatically re-initializes itself if it is exhausted: if a
* record is newly available, a subsequent call to the {@code next()} method will
* return {@code true} and the record will be available by calling {@code getRecord()}
* method.
*
* \@NotThreadSafe
*/
class FileReplicaDBCursor implements DBCursor<UpdateMsg>
{
/** The underlying cursor. */
private final RepositionableCursor<CSN, UpdateMsg> cursor;
/** The next record to return. */
private Record<CSN, UpdateMsg> nextRecord;
/** The CSN to re-start with in case the cursor is exhausted. */
private CSN lastNonNullCurrentCSN;
private PositionStrategy positionStrategy;
/**
* Creates the cursor from provided log cursor and start CSN.
*
* @param cursor
* The underlying log cursor to read log.
* @param startCSN
* The CSN to use as a start point (excluded from cursor, the lowest
* CSN higher than this CSN is used as the real start point).
* @param positionStrategy
* Cursor position strategy, which allow to choose if cursor must
* start from the provided CSN or just after the provided CSN.
*/
FileReplicaDBCursor(
final RepositionableCursor<CSN, UpdateMsg> cursor,
final CSN startCSN,
final PositionStrategy positionStrategy) {
this.cursor = cursor;
this.lastNonNullCurrentCSN = startCSN;
this.positionStrategy = positionStrategy;
}
/** {@inheritDoc} */
@Override
public UpdateMsg getRecord()
{
return nextRecord == null ? null : nextRecord.getValue();
}
/** {@inheritDoc} */
@Override
public boolean next() throws ChangelogException
{
if (cursor.next())
{
nextRecord = cursor.getRecord();
final int nextCSNCompare = nextRecord.getKey().compareTo(lastNonNullCurrentCSN);
if (nextCSNCompare > 0 || (nextCSNCompare == 0 && positionStrategy == ON_MATCHING_KEY))
{
// start CSN is found, switch to position strategy that always find the next
lastNonNullCurrentCSN = nextRecord.getKey();
positionStrategy = AFTER_MATCHING_KEY;
return true;
}
}
// either cursor is exhausted or we still have not reached the start CSN
return nextWhenCursorIsExhaustedOrNotCorrectlyPositionned();
}
/** Re-initialize the cursor after the last non null CSN. */
private boolean nextWhenCursorIsExhaustedOrNotCorrectlyPositionned() throws ChangelogException
{
final boolean found = cursor.positionTo(lastNonNullCurrentCSN, GREATER_THAN_OR_EQUAL_TO_KEY, positionStrategy);
if (found && cursor.next())
{
nextRecord = cursor.getRecord();
lastNonNullCurrentCSN = nextRecord.getKey();
return true;
}
nextRecord = null;
return false;
}
/** {@inheritDoc} */
@Override
public void close()
{
cursor.close();
}
}