001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hdfs.server.protocol;
019
020import java.util.Collections;
021import java.util.List;
022
023import com.google.common.base.Joiner;
024import com.google.common.base.Preconditions;
025
026/**
027 * An enumeration of logs available on a remote NameNode.
028 */
029public class RemoteEditLogManifest {
030
031  private List<RemoteEditLog> logs;
032  
033  public RemoteEditLogManifest() {
034  }
035  
036  public RemoteEditLogManifest(List<RemoteEditLog> logs) {
037    this.logs = logs;
038    checkState();
039  }
040  
041  
042  /**
043   * Check that the logs are non-overlapping sequences of transactions,
044   * in sorted order. They do not need to be contiguous.
045   * @throws IllegalStateException if incorrect
046   */
047  private void checkState()  {
048    Preconditions.checkNotNull(logs);
049    
050    RemoteEditLog prev = null;
051    for (RemoteEditLog log : logs) {
052      if (prev != null) {
053        if (log.getStartTxId() <= prev.getEndTxId()) {
054          throw new IllegalStateException(
055              "Invalid log manifest (log " + log + " overlaps " + prev + ")\n"
056              + this);
057        }
058      }
059      
060      prev = log;
061    }
062  }
063  
064  public List<RemoteEditLog> getLogs() {
065    return Collections.unmodifiableList(logs);
066  }
067
068
069  
070  @Override
071  public String toString() {
072    return "[" + Joiner.on(", ").join(logs) + "]";
073  }
074}