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.hbase.wal;
019
020import java.io.Closeable;
021import java.io.IOException;
022import java.util.List;
023import java.util.OptionalLong;
024import java.util.concurrent.CompletableFuture;
025import org.apache.hadoop.conf.Configuration;
026import org.apache.hadoop.hbase.Abortable;
027import org.apache.hadoop.hbase.client.RegionInfo;
028import org.apache.hadoop.hbase.regionserver.wal.AsyncFSWAL;
029import org.apache.hadoop.hbase.regionserver.wal.WALActionsListener;
030import org.apache.hadoop.hbase.replication.regionserver.WALFileLengthProvider;
031import org.apache.yetus.audience.InterfaceAudience;
032
033/**
034 * The Write Ahead Log (WAL) stores all durable edits to the HRegion. This interface provides the
035 * entry point for all WAL implementors.
036 * <p>
037 * See {@link FSHLogProvider} for an example implementation. A single WALProvider will be used for
038 * retrieving multiple WALs in a particular region server and must be threadsafe.
039 */
040@InterfaceAudience.Private
041public interface WALProvider {
042
043  /**
044   * Set up the provider to create wals. will only be called once per instance.
045   * @param factory    factory that made us may not be null
046   * @param conf       may not be null
047   * @param providerId differentiate between providers from one factory. may be null
048   */
049  void init(WALFactory factory, Configuration conf, String providerId, Abortable server)
050    throws IOException;
051
052  /**
053   * @param region the region which we want to get a WAL for it. Could be null.
054   * @return a WAL for writing entries for the given region.
055   */
056  WAL getWAL(RegionInfo region) throws IOException;
057
058  /** Returns the List of WALs that are used by this server */
059  List<WAL> getWALs();
060
061  /**
062   * persist outstanding WALs to storage and stop accepting new appends. This method serves as
063   * shorthand for sending a sync to every WAL provided by a given implementation. Those WALs will
064   * also stop accepting new writes.
065   */
066  void shutdown() throws IOException;
067
068  /**
069   * shutdown utstanding WALs and clean up any persisted state. Call this method only when you will
070   * not need to replay any of the edits to the WALs from this provider. After this call completes,
071   * the underlying resources should have been reclaimed.
072   */
073  void close() throws IOException;
074
075  interface WriterBase extends Closeable {
076    long getLength();
077
078    /**
079     * NOTE: We add this method for {@link WALFileLengthProvider} used for replication, considering
080     * the case if we use {@link AsyncFSWAL},we write to 3 DNs concurrently, according to the
081     * visibility guarantee of HDFS, the data will be available immediately when arriving at DN
082     * since all the DNs will be considered as the last one in pipeline. This means replication may
083     * read uncommitted data and replicate it to the remote cluster and cause data inconsistency.
084     * The method {@link WriterBase#getLength} may return length which just in hdfs client buffer
085     * and not successfully synced to HDFS, so we use this method to return the length successfully
086     * synced to HDFS and replication thread could only read writing WAL file limited by this
087     * length. see also HBASE-14004 and this document for more details:
088     * https://docs.google.com/document/d/11AyWtGhItQs6vsLRIx32PwTxmBY3libXwGXI25obVEY/edit#
089     * @return byteSize successfully synced to underlying filesystem.
090     */
091    long getSyncedLength();
092  }
093
094  // Writers are used internally. Users outside of the WAL should be relying on the
095  // interface provided by WAL.
096  interface Writer extends WriterBase {
097    void sync(boolean forceSync) throws IOException;
098
099    void append(WAL.Entry entry) throws IOException;
100  }
101
102  interface AsyncWriter extends WriterBase {
103    CompletableFuture<Long> sync(boolean forceSync);
104
105    void append(WAL.Entry entry);
106  }
107
108  /**
109   * Get number of the log files this provider is managing
110   */
111  long getNumLogFiles();
112
113  /**
114   * Get size of the log files this provider is managing
115   */
116  long getLogFileSize();
117
118  /**
119   * Add a {@link WALActionsListener}.
120   * <p>
121   * Notice that you must call this method before calling {@link #getWAL(RegionInfo)} as this method
122   * will not effect the {@link WAL} which has already been created. And as long as we can only it
123   * when initialization, it is not thread safe.
124   */
125  void addWALActionsListener(WALActionsListener listener);
126
127  default WALFileLengthProvider getWALFileLengthProvider() {
128    return path -> getWALs().stream().map(w -> w.getLogFileSizeIfBeingWritten(path))
129      .filter(o -> o.isPresent()).findAny().orElse(OptionalLong.empty());
130  }
131}