hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/namenode/LogsPurgeable.java

/**
 * 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;
import java.util.Collection;

/**
 * Interface used to abstract over classes which manage edit logs that may need
 * to be purged.
 */
interface LogsPurgeable {
  
  /**
   * Remove all edit logs with transaction IDs lower than the given transaction
   * ID.
   * 
   * @param minTxIdToKeep the lowest transaction ID that should be retained
   * @throws IOException in the event of error
   */
  public void purgeLogsOlderThan(long minTxIdToKeep) throws IOException;
  
  /**
   * Get a list of edit log input streams.  The list will start with the
   * stream that contains fromTxnId, and continue until the end of the journal
   * being managed.
   * 
   * @param fromTxId the first transaction id we want to read
   * @param inProgressOk whether or not in-progress streams should be returned
   * @param onlyDurableTxns whether or not streams should be bounded by durable
   *                        TxId. A durable TxId is the committed txid in QJM
   *                        or the largest txid written into file in FJM
   * @throws IOException if the underlying storage has an error or is otherwise
   * inaccessible
   */
  void selectInputStreams(Collection<EditLogInputStream> streams,
      long fromTxId, boolean inProgressOk, boolean onlyDurableTxns)
      throws IOException;
  
}