org.apache.hadoop.hbase.io

Class FSDataInputStreamWrapper

java.lang.Object

org.apache.hadoop.hbase.io.FSDataInputStreamWrapper

public class FSDataInputStreamWrapper
extends java.lang.Object

Wrapper for input stream(s) that takes care of the interaction of FS and HBase checksums, as well as closing streams. Initialization is not thread-safe, but normal operation is; see method comments.

Constructor Summary

Constructors

Constructor and Description
FSDataInputStreamWrapper(FileSystem fs, FileLink link)
FSDataInputStreamWrapper(FileSystem fs, Path path)
FSDataInputStreamWrapper(FSDataInputStream fsdis) For use in tests.
FSDataInputStreamWrapper(FSDataInputStream fsdis, FSDataInputStream noChecksum) For use in tests.

Method Summary

Modifier and Type	Method and Description
void	checksumOk() Report that checksum was ok, so we may ponder going back to HBase checksum.
void	close() Close stream(s) if necessary.
FSDataInputStream	fallbackToFsChecksum(int offCount) Read from non-checksum stream failed, fall back to FS checksum.
HFileSystem	getHfs()
FSDataInputStream	getStream(boolean useHBaseChecksum) Get the stream to use.
void	prepareForBlockReader(boolean forceNoHBaseChecksum) Prepares the streams for block reader.
boolean	shouldUseHBaseChecksum()
void	unbuffer() This will free sockets and file descriptors held by the stream only when the stream implements org.apache.hadoop.fs.CanUnbuffer.

Methods inherited from class java.lang.Object

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

Constructor Detail

FSDataInputStreamWrapper

public FSDataInputStreamWrapper(FileSystem fs,
                                Path path)
                         throws java.io.IOException

Throws:

java.io.IOException

FSDataInputStreamWrapper

public FSDataInputStreamWrapper(FileSystem fs,
                                FileLink link)
                         throws java.io.IOException

Throws:

java.io.IOException

FSDataInputStreamWrapper

public FSDataInputStreamWrapper(FSDataInputStream fsdis)

For use in tests.

FSDataInputStreamWrapper

public FSDataInputStreamWrapper(FSDataInputStream fsdis,
                                FSDataInputStream noChecksum)

For use in tests.

Method Detail

prepareForBlockReader

public void prepareForBlockReader(boolean forceNoHBaseChecksum)
                           throws java.io.IOException

Prepares the streams for block reader. NOT THREAD SAFE. Must be called once, after any reads finish and before any other reads start (what happens in reality is we read the tail, then call this based on what's in the tail, then read blocks).

Parameters:

forceNoHBaseChecksum - Force not using HBase checksum.

Throws:

java.io.IOException

shouldUseHBaseChecksum

public boolean shouldUseHBaseChecksum()

Returns:

Whether we are presently using HBase checksum.

getStream

public FSDataInputStream getStream(boolean useHBaseChecksum)

Get the stream to use. Thread-safe.

Parameters:

useHBaseChecksum - must be the value that shouldUseHBaseChecksum has returned at some point in the past, otherwise the result is undefined.

fallbackToFsChecksum

public FSDataInputStream fallbackToFsChecksum(int offCount)
                                       throws java.io.IOException

Read from non-checksum stream failed, fall back to FS checksum. Thread-safe.

Parameters:

offCount - For how many checksumOk calls to turn off the HBase checksum.

Throws:

java.io.IOException

checksumOk

public void checksumOk()

Report that checksum was ok, so we may ponder going back to HBase checksum.

close

public void close()
           throws java.io.IOException

Close stream(s) if necessary.

Throws:

java.io.IOException

getHfs

public HFileSystem getHfs()

unbuffer

public void unbuffer()

This will free sockets and file descriptors held by the stream only when the stream implements org.apache.hadoop.fs.CanUnbuffer. NOT THREAD SAFE. Must be called only when all the clients using this stream to read the blocks have finished reading. If by chance the stream is unbuffered and there are clients still holding this stream for read then on next client read request a new socket will be opened by Datanode without client knowing about it and will serve its read request. Note: If this socket is idle for some time then the DataNode will close the socket and the socket will move into CLOSE_WAIT state and on the next client request on this stream, the current socket will be closed and a new socket will be opened to serve the requests.