001/** 002 * 003 * Licensed to the Apache Software Foundation (ASF) under one 004 * or more contributor license agreements. See the NOTICE file 005 * distributed with this work for additional information 006 * regarding copyright ownership. The ASF licenses this file 007 * to you under the Apache License, Version 2.0 (the 008 * "License"); you may not use this file except in compliance 009 * with the License. You may obtain a copy of the License at 010 * 011 * http://www.apache.org/licenses/LICENSE-2.0 012 * 013 * Unless required by applicable law or agreed to in writing, software 014 * distributed under the License is distributed on an "AS IS" BASIS, 015 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 016 * See the License for the specific language governing permissions and 017 * limitations under the License. 018 */ 019package org.apache.hadoop.hbase.wal; 020 021import java.io.Closeable; 022import java.io.IOException; 023import java.util.List; 024import java.util.OptionalLong; 025import java.util.concurrent.CompletableFuture; 026 027import org.apache.hadoop.conf.Configuration; 028import org.apache.hadoop.hbase.Abortable; 029import org.apache.hadoop.hbase.client.RegionInfo; 030import org.apache.hadoop.hbase.regionserver.wal.AsyncFSWAL; 031import org.apache.hadoop.hbase.regionserver.wal.WALActionsListener; 032import org.apache.hadoop.hbase.replication.regionserver.WALFileLengthProvider; 033import org.apache.yetus.audience.InterfaceAudience; 034 035/** 036 * The Write Ahead Log (WAL) stores all durable edits to the HRegion. This interface provides the 037 * entry point for all WAL implementors. 038 * <p> 039 * See {@link FSHLogProvider} for an example implementation. A single WALProvider will be used for 040 * retrieving multiple WALs in a particular region server and must be threadsafe. 041 */ 042@InterfaceAudience.Private 043public interface WALProvider { 044 045 /** 046 * Set up the provider to create wals. will only be called once per instance. 047 * @param factory factory that made us may not be null 048 * @param conf may not be null 049 * @param providerId differentiate between providers from one factory. may be null 050 */ 051 void init(WALFactory factory, Configuration conf, String providerId, Abortable abortable) 052 throws IOException; 053 054 /** 055 * @param region the region which we want to get a WAL for it. Could be null. 056 * @return a WAL for writing entries for the given region. 057 */ 058 WAL getWAL(RegionInfo region) throws IOException; 059 060 /** 061 * @return the List of WALs that are used by this server 062 */ 063 List<WAL> getWALs(); 064 065 /** 066 * persist outstanding WALs to storage and stop accepting new appends. This method serves as 067 * shorthand for sending a sync to every WAL provided by a given implementation. Those WALs will 068 * also stop accepting new writes. 069 */ 070 void shutdown() throws IOException; 071 072 /** 073 * shutdown utstanding WALs and clean up any persisted state. Call this method only when you will 074 * not need to replay any of the edits to the WALs from this provider. After this call completes, 075 * the underlying resources should have been reclaimed. 076 */ 077 void close() throws IOException; 078 079 interface WriterBase extends Closeable { 080 long getLength(); 081 /** 082 * NOTE: We add this method for {@link WALFileLengthProvider} used for replication, 083 * considering the case if we use {@link AsyncFSWAL},we write to 3 DNs concurrently, 084 * according to the visibility guarantee of HDFS, the data will be available immediately 085 * when arriving at DN since all the DNs will be considered as the last one in pipeline. 086 * This means replication may read uncommitted data and replicate it to the remote cluster 087 * and cause data inconsistency. 088 * The method {@link WriterBase#getLength} may return length which just in hdfs client 089 * buffer and not successfully synced to HDFS, so we use this method to return the length 090 * successfully synced to HDFS and replication thread could only read writing WAL file 091 * limited by this length. 092 * see also HBASE-14004 and this document for more details: 093 * https://docs.google.com/document/d/11AyWtGhItQs6vsLRIx32PwTxmBY3libXwGXI25obVEY/edit# 094 * @return byteSize successfully synced to underlying filesystem. 095 */ 096 long getSyncedLength(); 097 } 098 099 // Writers are used internally. Users outside of the WAL should be relying on the 100 // interface provided by WAL. 101 interface Writer extends WriterBase { 102 void sync(boolean forceSync) throws IOException; 103 104 void append(WAL.Entry entry) throws IOException; 105 } 106 107 interface AsyncWriter extends WriterBase { 108 CompletableFuture<Long> sync(boolean forceSync); 109 110 void append(WAL.Entry entry); 111 } 112 113 /** 114 * Get number of the log files this provider is managing 115 */ 116 long getNumLogFiles(); 117 118 /** 119 * Get size of the log files this provider is managing 120 */ 121 long getLogFileSize(); 122 123 /** 124 * Add a {@link WALActionsListener}. 125 * <p> 126 * Notice that you must call this method before calling {@link #getWAL(RegionInfo)} as this method 127 * will not effect the {@link WAL} which has already been created. And as long as we can only it 128 * when initialization, it is not thread safe. 129 */ 130 void addWALActionsListener(WALActionsListener listener); 131 132 default WALFileLengthProvider getWALFileLengthProvider() { 133 return path -> getWALs().stream().map(w -> w.getLogFileSizeIfBeingWritten(path)) 134 .filter(o -> o.isPresent()).findAny().orElse(OptionalLong.empty()); 135 } 136}