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     */
018    package org.apache.hadoop.hdfs.server.protocol;
019    
020    import java.util.Collections;
021    import java.util.List;
022    
023    import com.google.common.base.Joiner;
024    import com.google.common.base.Preconditions;
025    
026    /**
027     * An enumeration of logs available on a remote NameNode.
028     */
029    public 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    }