org.apache.hadoop.hbase.regionserver.wal

Class ProtobufLogReader

java.lang.Object

org.apache.hadoop.hbase.regionserver.wal.ReaderBase

org.apache.hadoop.hbase.regionserver.wal.ProtobufLogReader

All Implemented Interfaces:

HLog.Reader

@InterfaceAudience.Private
public class ProtobufLogReader
extends ReaderBase

A Protobuf based WAL has the following structure:

<PB_WAL_MAGIC><WALHeader><WALEdits>...<WALEdits><Trailer> <TrailerSize> <PB_WAL_COMPLETE_MAGIC>

The Reader reads meta information (WAL Compression state, WALTrailer, etc) in initReader(FSDataInputStream). A WALTrailer is an extensible structure which is appended at the end of the WAL. This is empty for now; it can contain some meta information such as Region level stats, etc in future.

Field Summary

Fields inherited from class org.apache.hadoop.hbase.regionserver.wal.ReaderBase

compressionContext, conf, edit, emptyCompressionContext, fileLength, fs, path, trailer, trailerWarnSize

Constructor Summary

Constructors

Constructor and Description
ProtobufLogReader()

Method Summary

Methods

Modifier and Type	Method and Description
void	close()
long	getPosition()
WALProtos.WALTrailer	getWALTrailer()
protected boolean	hasCompression()
protected void	initAfterCompression() Initializes the compression after the shared stuff has been initialized.
protected void	initReader(org.apache.hadoop.fs.FSDataInputStream stream) Initializes the log reader with a particular stream (may be null).
protected boolean	readNext(HLog.Entry entry) Read next entry.
void	reset()
protected void	seekOnFs(long pos) Performs a filesystem-level seek to a certain position in an underlying file.

Methods inherited from class org.apache.hadoop.hbase.regionserver.wal.ReaderBase

init, next, next, seek

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ProtobufLogReader

public ProtobufLogReader()

Method Detail

close

public void close()
           throws IOException

Throws:

IOException

getPosition

public long getPosition()
                 throws IOException

Throws:

IOException

reset

public void reset()
           throws IOException

Throws:

IOException

initReader

protected void initReader(org.apache.hadoop.fs.FSDataInputStream stream)
                   throws IOException

Description copied from class: ReaderBase

Initializes the log reader with a particular stream (may be null). Reader assumes ownership of the stream if not null and may use it. Called once.

Specified by:

initReader in class ReaderBase

Throws:

IOException

initAfterCompression

protected void initAfterCompression()
                             throws IOException

Description copied from class: ReaderBase

Initializes the compression after the shared stuff has been initialized. Called once.

Specified by:

initAfterCompression in class ReaderBase

Throws:

IOException

hasCompression

protected boolean hasCompression()

Specified by:

hasCompression in class ReaderBase

Returns:

Whether compression is enabled for this log.

readNext

protected boolean readNext(HLog.Entry entry)
                    throws IOException

Description copied from class: ReaderBase

Read next entry.

Specified by:

readNext in class ReaderBase

Parameters:

entry - The entry to read into.

Returns:

Whether there was anything to read.

Throws:

IOException

getWALTrailer

public WALProtos.WALTrailer getWALTrailer()

Specified by:

getWALTrailer in interface HLog.Reader

Overrides:

getWALTrailer in class ReaderBase

Returns:

the WALTrailer of the current HLog. It may be null in case of legacy or corrupt WAL files.

seekOnFs

protected void seekOnFs(long pos)
                 throws IOException

Description copied from class: ReaderBase

Performs a filesystem-level seek to a certain position in an underlying file.

Specified by:

seekOnFs in class ReaderBase

Throws:

IOException