org.apache.hadoop.hbase.io

Class FSDataInputStreamWrapper

java.lang.Object

org.apache.hadoop.hbase.io.FSDataInputStreamWrapper

All Implemented Interfaces:

Closeable, AutoCloseable

@InterfaceAudience.Private
public class FSDataInputStreamWrapper
extends Object
implements Closeable

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.

Field Summary

Fields

Modifier and Type	Field and Description
private boolean	doCloseStreams
private boolean	dropBehind
private AtomicInteger	hbaseChecksumOffCount
private HFileSystem	hfs
private Boolean	instanceOfCanUnbuffer
private static boolean	isLogTraceEnabled
private FileLink	link
private static org.slf4j.Logger	LOG
private org.apache.hadoop.fs.Path	path
private long	readahead
private org.apache.hadoop.fs.FSDataInputStream	stream Two stream handles, one with and one without FS-level checksum.
private org.apache.hadoop.fs.FSDataInputStream	streamNoFsChecksum
private Object	streamNoFsChecksumFirstCreateLock
private Method	unbuffer
private boolean	useHBaseChecksum
private boolean	useHBaseChecksumConfigured

Constructor Summary

Constructors

Modifier	Constructor and Description
	FSDataInputStreamWrapper(org.apache.hadoop.fs.FileSystem fs, FileLink link, boolean dropBehind, long readahead)
private	FSDataInputStreamWrapper(org.apache.hadoop.fs.FileSystem fs, FileLink link, org.apache.hadoop.fs.Path path, boolean dropBehind, long readahead)
	FSDataInputStreamWrapper(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path path)
	FSDataInputStreamWrapper(org.apache.hadoop.fs.FileSystem fs, org.apache.hadoop.fs.Path path, boolean dropBehind, long readahead)
	FSDataInputStreamWrapper(org.apache.hadoop.fs.FSDataInputStream fsdis) For use in tests.
	FSDataInputStreamWrapper(org.apache.hadoop.fs.FSDataInputStream fsdis, org.apache.hadoop.fs.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.
org.apache.hadoop.fs.FSDataInputStream	fallbackToFsChecksum(int offCount) Read from non-checksum stream failed, fall back to FS checksum.
HFileSystem	getHfs()
org.apache.hadoop.fs.FSDataInputStream	getStream(boolean useHBaseChecksum) Get the stream to use.
void	prepareForBlockReader(boolean forceNoHBaseChecksum) Prepares the streams for block reader.
private void	setStreamOptions(org.apache.hadoop.fs.FSDataInputStream in)
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

Field Detail

LOG

private static final org.slf4j.Logger LOG

isLogTraceEnabled

private static final boolean isLogTraceEnabled

hfs

private final HFileSystem hfs

path

private final org.apache.hadoop.fs.Path path

link

private final FileLink link

doCloseStreams

private final boolean doCloseStreams

dropBehind

private final boolean dropBehind

readahead

private final long readahead

stream

private volatile org.apache.hadoop.fs.FSDataInputStream stream

Two stream handles, one with and one without FS-level checksum. HDFS checksum setting is on FS level, not single read level, so you have to keep two FS objects and two handles open to interleave different reads freely, which is very sad. This is what we do: 1) First, we need to read the trailer of HFile to determine checksum parameters. We always use FS checksum to do that, so ctor opens stream. 2.1) After that, if HBase checksum is not used, we'd just always use stream; 2.2) If HBase checksum can be used, we'll open streamNoFsChecksum, and close stream. User MUST call prepareForBlockReader for that to happen; if they don't, (2.1) will be the default. 3) The users can call shouldUseHBaseChecksum(), and pass its result to getStream(boolean) to get stream (if Java had out/pointer params we could return both in one call). This stream is guaranteed to be set. 4) The first time HBase checksum fails, one would call fallbackToFsChecksum(int). That will take lock, and open stream. While this is going on, others will continue to use the old stream; if they also want to fall back, they'll also call fallbackToFsChecksum(int), and block until stream is set. 5) After some number of checksumOk() calls, we will go back to using HBase checksum. We will have 2 handles; however we presume checksums fail so rarely that we don't care.

streamNoFsChecksum

private volatile org.apache.hadoop.fs.FSDataInputStream streamNoFsChecksum

streamNoFsChecksumFirstCreateLock

private final Object streamNoFsChecksumFirstCreateLock

useHBaseChecksumConfigured

private boolean useHBaseChecksumConfigured

useHBaseChecksum

private volatile boolean useHBaseChecksum

hbaseChecksumOffCount

private AtomicInteger hbaseChecksumOffCount

instanceOfCanUnbuffer

private Boolean instanceOfCanUnbuffer

unbuffer

private Method unbuffer

Constructor Detail

FSDataInputStreamWrapper

public FSDataInputStreamWrapper(org.apache.hadoop.fs.FileSystem fs,
                                org.apache.hadoop.fs.Path path)
                         throws IOException

Throws:

IOException

FSDataInputStreamWrapper

public FSDataInputStreamWrapper(org.apache.hadoop.fs.FileSystem fs,
                                org.apache.hadoop.fs.Path path,
                                boolean dropBehind,
                                long readahead)
                         throws IOException

Throws:

IOException

FSDataInputStreamWrapper

public FSDataInputStreamWrapper(org.apache.hadoop.fs.FileSystem fs,
                                FileLink link,
                                boolean dropBehind,
                                long readahead)
                         throws IOException

Throws:

IOException

FSDataInputStreamWrapper

private FSDataInputStreamWrapper(org.apache.hadoop.fs.FileSystem fs,
                                 FileLink link,
                                 org.apache.hadoop.fs.Path path,
                                 boolean dropBehind,
                                 long readahead)
                          throws IOException

Throws:

IOException

FSDataInputStreamWrapper

public FSDataInputStreamWrapper(org.apache.hadoop.fs.FSDataInputStream fsdis)

For use in tests.

FSDataInputStreamWrapper

public FSDataInputStreamWrapper(org.apache.hadoop.fs.FSDataInputStream fsdis,
                                org.apache.hadoop.fs.FSDataInputStream noChecksum)

For use in tests.

Method Detail

setStreamOptions

private void setStreamOptions(org.apache.hadoop.fs.FSDataInputStream in)

prepareForBlockReader

public void prepareForBlockReader(boolean forceNoHBaseChecksum)
                           throws 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:

IOException

shouldUseHBaseChecksum

public boolean shouldUseHBaseChecksum()

Returns:

Whether we are presently using HBase checksum.

getStream

public org.apache.hadoop.fs.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 org.apache.hadoop.fs.FSDataInputStream fallbackToFsChecksum(int offCount)
                                                            throws 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:

IOException

checksumOk

public void checksumOk()

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

close

public void close()

Close stream(s) if necessary.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

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.