org.apache.hadoop.hbase.wal

Interface WALProvider.WriterBase

All Superinterfaces:

AutoCloseable, Closeable

All Known Subinterfaces:

AsyncFSWALProvider.AsyncWriter, FSHLogProvider.Writer, WALProvider.AsyncWriter, WALProvider.Writer

All Known Implementing Classes:

AsyncProtobufLogWriter, ProtobufLogWriter, SecureAsyncProtobufLogWriter, SecureProtobufLogWriter

Enclosing interface:

WALProvider

public static interface WALProvider.WriterBase
extends Closeable

Method Summary

Modifier and Type	Method and Description
long	getLength()
long	getSyncedLength() NOTE: We add this method for WALFileLengthProvider used for replication, considering the case if we use 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.

Methods inherited from interface java.io.Closeable

close

Method Detail

getLength

long getLength()

getSyncedLength

long getSyncedLength()

NOTE: We add this method for WALFileLengthProvider used for replication, considering the case if we use 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 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#

Returns:

byteSize successfully synced to underlying filesystem.