Package com.wavefront.agent.queueing

Class ConcurrentShardedQueueFile

java.lang.Object

com.wavefront.agent.queueing.ConcurrentShardedQueueFile

All Implemented Interfaces:

QueueFile, Closeable, AutoCloseable, Iterable<byte[]>

public class ConcurrentShardedQueueFile
extends Object
implements QueueFile

A thread-safe QueueFile implementation, that uses multiple smaller "shard" files instead of one large file. This also improves concurrency - when we have more than one file, we can add and remove tasks at the same time without mutually exclusive locking.

Author:

[email protected]

Constructor Summary

Constructors

Constructor	Description
ConcurrentShardedQueueFile(String fileNamePrefix, String fileNameSuffix, int shardSizeBytes, QueueFileFactory queueFileFactory)

Method Summary

Modifier and Type	Method	Description
void	add(byte[] data, int offset, int count)	Adds an element to the end of the queue.
long	availableBytes()	Returns the number of bytes available for adding new tasks without growing the file.
void	clear()	Clears this queue.
void	close()
Iterator<byte[]>	iterator()
byte[]	peek()	Reads the eldest element.
void	remove()	Removes the eldest element.
int	size()	Returns the number of elements in this queue.
long	storageBytes()	Returns the storage size (on-disk file size) in bytes.
long	usedBytes()	Returns the number of bytes used for data.

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Methods inherited from interface com.wavefront.agent.queueing.QueueFile

add, isEmpty

Constructor Detail

ConcurrentShardedQueueFile

public ConcurrentShardedQueueFile(String fileNamePrefix,
                                  String fileNameSuffix,
                                  int shardSizeBytes,
                                  QueueFileFactory queueFileFactory)
                           throws IOException

Parameters:

fileNamePrefix - path + file name prefix for shard files

fileNameSuffix - file name suffix to identify shard files

shardSizeBytes - target shard size bytes

queueFileFactory - factory for QueueFile objects

Throws:

IOException - if file(s) could not be created or accessed

Method Detail

peek

@Nullable
public byte[] peek()
            throws IOException

Description copied from interface: QueueFile

Reads the eldest element. Returns null if the queue is empty.

Specified by:

peek in interface QueueFile

Returns:

the eldest element.

Throws:

IOException

add

public void add(byte[] data,
                int offset,
                int count)
         throws IOException

Description copied from interface: QueueFile

Adds an element to the end of the queue.

Specified by:

add in interface QueueFile

Parameters:

data - to copy bytes from

offset - to start from in buffer

count - number of bytes to copy

Throws:

IOException

remove

public void remove()
            throws IOException

Description copied from interface: QueueFile

Removes the eldest element.

Specified by:

remove in interface QueueFile

Throws:

IOException

size

public int size()

Description copied from interface: QueueFile

Returns the number of elements in this queue.

Specified by:

size in interface QueueFile

storageBytes

public long storageBytes()

Description copied from interface: QueueFile

Returns the storage size (on-disk file size) in bytes.

Specified by:

storageBytes in interface QueueFile

Returns:

file size in bytes.

usedBytes

public long usedBytes()

Description copied from interface: QueueFile

Returns the number of bytes used for data.

Specified by:

usedBytes in interface QueueFile

Returns:

bytes used.

availableBytes

public long availableBytes()

Description copied from interface: QueueFile

Returns the number of bytes available for adding new tasks without growing the file.

Specified by:

availableBytes in interface QueueFile

Returns:

bytes available.

close

public void close()
           throws IOException

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Throws:

IOException

clear

public void clear()
           throws IOException

Description copied from interface: QueueFile

Clears this queue. Truncates the file to the initial size.

Specified by:

clear in interface QueueFile

Throws:

IOException

iterator

@Nonnull
public Iterator<byte[]> iterator()

Specified by:

iterator in interface Iterable<byte[]>