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.namenode; 019 020import java.io.Closeable; 021import java.io.IOException; 022 023import org.apache.hadoop.classification.InterfaceAudience; 024import org.apache.hadoop.classification.InterfaceStability; 025import org.apache.hadoop.hdfs.server.common.Storage.FormatConfirmable; 026import org.apache.hadoop.hdfs.server.protocol.NamespaceInfo; 027 028/** 029 * A JournalManager is responsible for managing a single place of storing 030 * edit logs. It may correspond to multiple files, a backup node, etc. 031 * Even when the actual underlying storage is rolled, or failed and restored, 032 * each conceptual place of storage corresponds to exactly one instance of 033 * this class, which is created when the EditLog is first opened. 034 */ 035@InterfaceAudience.Private 036@InterfaceStability.Evolving 037public interface JournalManager extends Closeable, LogsPurgeable, 038 FormatConfirmable { 039 040 /** 041 * Format the underlying storage, removing any previously 042 * stored data. 043 */ 044 void format(NamespaceInfo ns) throws IOException; 045 046 /** 047 * Begin writing to a new segment of the log stream, which starts at 048 * the given transaction ID. 049 */ 050 EditLogOutputStream startLogSegment(long txId) throws IOException; 051 052 /** 053 * Mark the log segment that spans from firstTxId to lastTxId 054 * as finalized and complete. 055 */ 056 void finalizeLogSegment(long firstTxId, long lastTxId) throws IOException; 057 058 /** 059 * Set the amount of memory that this stream should use to buffer edits 060 */ 061 void setOutputBufferCapacity(int size); 062 063 /** 064 * Recover segments which have not been finalized. 065 */ 066 void recoverUnfinalizedSegments() throws IOException; 067 068 /** 069 * Close the journal manager, freeing any resources it may hold. 070 */ 071 @Override 072 void close() throws IOException; 073 074 /** 075 * Indicate that a journal is cannot be used to load a certain range of 076 * edits. 077 * This exception occurs in the case of a gap in the transactions, or a 078 * corrupt edit file. 079 */ 080 public static class CorruptionException extends IOException { 081 static final long serialVersionUID = -4687802717006172702L; 082 083 public CorruptionException(String reason) { 084 super(reason); 085 } 086 } 087}