1 /** 2 * 3 * Licensed to the Apache Software Foundation (ASF) under one 4 * or more contributor license agreements. See the NOTICE file 5 * distributed with this work for additional information 6 * regarding copyright ownership. The ASF licenses this file 7 * to you under the Apache License, Version 2.0 (the 8 * "License"); you may not use this file except in compliance 9 * with the License. You may obtain a copy of the License at 10 * 11 * http://www.apache.org/licenses/LICENSE-2.0 12 * 13 * Unless required by applicable law or agreed to in writing, software 14 * distributed under the License is distributed on an "AS IS" BASIS, 15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 * See the License for the specific language governing permissions and 17 * limitations under the License. 18 */ 19 package org.apache.hadoop.hbase.wal; 20 21 import java.io.Closeable; 22 import java.io.IOException; 23 import java.util.List; 24 25 import org.apache.hadoop.hbase.classification.InterfaceAudience; 26 import org.apache.hadoop.hbase.classification.InterfaceStability; 27 import org.apache.hadoop.conf.Configuration; 28 29 // imports for things that haven't moved from regionserver.wal yet. 30 import org.apache.hadoop.hbase.regionserver.wal.WALActionsListener; 31 32 /** 33 * The Write Ahead Log (WAL) stores all durable edits to the HRegion. 34 * This interface provides the entry point for all WAL implementors. 35 * <p> 36 * See {@link DefaultWALProvider} for an example implementation. 37 * 38 * A single WALProvider will be used for retrieving multiple WALs in a particular region server 39 * and must be threadsafe. 40 */ 41 @InterfaceAudience.Private 42 public interface WALProvider { 43 44 /** 45 * Set up the provider to create wals. 46 * will only be called once per instance. 47 * @param factory factory that made us may not be null 48 * @param conf may not be null 49 * @param listeners may be null 50 * @param providerId differentiate between providers from one factory. may be null 51 */ init(final WALFactory factory, final Configuration conf, final List<WALActionsListener> listeners, final String providerId)52 void init(final WALFactory factory, final Configuration conf, 53 final List<WALActionsListener> listeners, final String providerId) throws IOException; 54 55 /** 56 * @param identifier may not be null. contents will not be altered. 57 * @return a WAL for writing entries for the given region. 58 */ getWAL(final byte[] identifier)59 WAL getWAL(final byte[] identifier) throws IOException; 60 61 /** 62 * persist outstanding WALs to storage and stop accepting new appends. 63 * This method serves as shorthand for sending a sync to every WAL provided by a given 64 * implementation. Those WALs will also stop accepting new writes. 65 */ shutdown()66 void shutdown() throws IOException; 67 68 /** 69 * shutdown utstanding WALs and clean up any persisted state. 70 * Call this method only when you will not need to replay any of the edits to the WALs from 71 * this provider. After this call completes, the underlying resources should have been reclaimed. 72 */ close()73 void close() throws IOException; 74 75 // Writers are used internally. Users outside of the WAL should be relying on the 76 // interface provided by WAL. 77 interface Writer extends Closeable { sync()78 void sync() throws IOException; append(WAL.Entry entry)79 void append(WAL.Entry entry) throws IOException; getLength()80 long getLength() throws IOException; 81 } 82 83 } 84