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* Licensed to the Apache Software Foundation (ASF) under one
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* to you under the Apache License, Version 2.0 (the
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*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
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* See the License for the specific language governing permissions and
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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());
}
}