/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hdfs.server.namenode;
import java.io.IOException;
/**
* A JournalManager is responsible for managing a single place of storing
* edit logs. It may correspond to multiple files, a backup node, etc.
* Even when the actual underlying storage is rolled, or failed and restored,
* each conceptual place of storage corresponds to exactly one instance of
* this class, which is created when the EditLog is first opened.
*/
interface JournalManager {
/**
* Begin writing to a new segment of the log stream, which starts at
* the given transaction ID.
*/
EditLogOutputStream startLogSegment(long txId) throws IOException;
/**
* Mark the log segment that spans from firstTxId to lastTxId
* as finalized and complete.
*/
void finalizeLogSegment(long firstTxId, long lastTxId) throws IOException;
/**
* Set the amount of memory that this stream should use to buffer edits
*/
void setOutputBufferCapacity(int size);
/**
* The JournalManager may archive/purge any logs for transactions less than
* or equal to minImageTxId.
*
* @param minTxIdToKeep the earliest txid that must be retained after purging
* old logs
* @param purger the purging implementation to use
* @throws IOException if purging fails
*/
void purgeLogsOlderThan(long minTxIdToKeep)
throws IOException;
/**
* @return an EditLogInputStream that reads from the same log that
* the edit log is currently writing. May return null if this journal
* manager does not support this operation.
*/
EditLogInputStream getInProgressInputStream(long segmentStartsAtTxId)
throws IOException;
}