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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
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 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
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 *     http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.hadoop.hbase.wal;

import java.io.Closeable;
import java.io.IOException;
import java.util.List;
import java.util.OptionalLong;
import java.util.concurrent.CompletableFuture;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.Abortable;
import org.apache.hadoop.hbase.client.RegionInfo;
import org.apache.hadoop.hbase.regionserver.wal.AsyncFSWAL;
import org.apache.hadoop.hbase.regionserver.wal.WALActionsListener;
import org.apache.hadoop.hbase.replication.regionserver.WALFileLengthProvider;
import org.apache.yetus.audience.InterfaceAudience;

/**
 * The Write Ahead Log (WAL) stores all durable edits to the HRegion. This interface provides the
 * entry point for all WAL implementors.
 * 

* See {@link FSHLogProvider} for an example implementation. A single WALProvider will be used for * retrieving multiple WALs in a particular region server and must be threadsafe. */ @InterfaceAudience.Private public interface WALProvider { /** * Set up the provider to create wals. will only be called once per instance. * @param factory factory that made us may not be null * @param conf may not be null * @param providerId differentiate between providers from one factory. may be null */ void init(WALFactory factory, Configuration conf, String providerId, Abortable abortable) throws IOException; /** * @param region the region which we want to get a WAL for it. Could be null. * @return a WAL for writing entries for the given region. */ WAL getWAL(RegionInfo region) throws IOException; /** Returns the List of WALs that are used by this server */ List getWALs(); /** * persist outstanding WALs to storage and stop accepting new appends. This method serves as * shorthand for sending a sync to every WAL provided by a given implementation. Those WALs will * also stop accepting new writes. */ void shutdown() throws IOException; /** * shutdown utstanding WALs and clean up any persisted state. Call this method only when you will * not need to replay any of the edits to the WALs from this provider. After this call completes, * the underlying resources should have been reclaimed. */ void close() throws IOException; interface WriterBase extends Closeable { long getLength(); /** * NOTE: We add this method for {@link WALFileLengthProvider} used for replication, considering * the case if we use {@link AsyncFSWAL},we write to 3 DNs concurrently, according to the * visibility guarantee of HDFS, the data will be available immediately when arriving at DN * since all the DNs will be considered as the last one in pipeline. This means replication may * read uncommitted data and replicate it to the remote cluster and cause data inconsistency. * The method {@link WriterBase#getLength} may return length which just in hdfs client buffer * and not successfully synced to HDFS, so we use this method to return the length successfully * synced to HDFS and replication thread could only read writing WAL file limited by this * length. see also HBASE-14004 and this document for more details: * https://docs.google.com/document/d/11AyWtGhItQs6vsLRIx32PwTxmBY3libXwGXI25obVEY/edit# * @return byteSize successfully synced to underlying filesystem. */ long getSyncedLength(); } // Writers are used internally. Users outside of the WAL should be relying on the // interface provided by WAL. interface Writer extends WriterBase { void sync(boolean forceSync) throws IOException; void append(WAL.Entry entry) throws IOException; } interface AsyncWriter extends WriterBase { CompletableFuture sync(boolean forceSync); void append(WAL.Entry entry); } /** * Get number of the log files this provider is managing */ long getNumLogFiles(); /** * Get size of the log files this provider is managing */ long getLogFileSize(); /** * Add a {@link WALActionsListener}. *

* Notice that you must call this method before calling {@link #getWAL(RegionInfo)} as this method * will not effect the {@link WAL} which has already been created. And as long as we can only it * when initialization, it is not thread safe. */ void addWALActionsListener(WALActionsListener listener); default WALFileLengthProvider getWALFileLengthProvider() { return path -> getWALs().stream().map(w -> w.getLogFileSizeIfBeingWritten(path)) .filter(o -> o.isPresent()).findAny().orElse(OptionalLong.empty()); } }





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