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.io.DataInput;
021import java.io.DataOutput;
022import java.io.IOException;
023import java.util.Collections;
024import java.util.List;
025
026import org.apache.hadoop.io.Writable;
027
028import com.google.common.base.Joiner;
029import com.google.common.base.Preconditions;
030import com.google.common.collect.Lists;
031
032/**
033 * An enumeration of logs available on a remote NameNode.
034 */
035public class RemoteEditLogManifest implements Writable {
036
037  private List<RemoteEditLog> logs;
038  
039  public RemoteEditLogManifest() {
040  }
041  
042  public RemoteEditLogManifest(List<RemoteEditLog> logs) {
043    this.logs = logs;
044    checkState();
045  }
046  
047  
048  /**
049   * Check that the logs are contiguous and non-overlapping
050   * sequences of transactions, in sorted order
051   * @throws IllegalStateException if incorrect
052   */
053  private void checkState()  {
054    Preconditions.checkNotNull(logs);
055    
056    RemoteEditLog prev = null;
057    for (RemoteEditLog log : logs) {
058      if (prev != null) {
059        if (log.getStartTxId() != prev.getEndTxId() + 1) {
060          throw new IllegalStateException("Invalid log manifest:" + this);
061        }
062      }
063      
064      prev = log;
065    }
066  }
067  
068  public List<RemoteEditLog> getLogs() {
069    return Collections.unmodifiableList(logs);
070  }
071
072
073  
074  @Override
075  public String toString() {
076    return "[" + Joiner.on(", ").join(logs) + "]";
077  }
078  
079  
080  @Override
081  public void write(DataOutput out) throws IOException {
082    out.writeInt(logs.size());
083    for (RemoteEditLog log : logs) {
084      log.write(out);
085    }
086  }
087
088  @Override
089  public void readFields(DataInput in) throws IOException {
090    int numLogs = in.readInt();
091    logs = Lists.newArrayList();
092    for (int i = 0; i < numLogs; i++) {
093      RemoteEditLog log = new RemoteEditLog();
094      log.readFields(in);
095      logs.add(log);
096    }
097    checkState();
098  }
099}