com.hp.nbio

Class MessageBuffer<M extends Message>

java.lang.Object

com.hp.nbio.MessageBuffer<M>

Type Parameters:

M - message type

public abstract class MessageBuffer<M extends Message>
extends Object

Abstraction of a bidirectional message transfer buffer backed by a byte channel and driven by an I/O loop.

Implementations are expected to provide means to get and put a message into the provided byte buffers.

Writers feed the data in form of messages via one of the queue(java.util.List<M>) methods and the data will get flushed

Author:

Thomas Vachuska

Field Summary

Fields

Modifier and Type	Field and Description
protected static int	BUFFER_SIZE Initial buffer size for in-bound & out-bound byte buffers.
protected static double	GROWTH_FACTOR Default growth factor for the out-bound byte buffer.
protected org.slf4j.Logger	log Shared logger.
protected static int	MAX_AGE Default maximum age in milliseconds before the buffer becomes stale.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	MessageBuffer(ByteChannel ch, IOLoop<M,?> loop) Creates a message buffer backed by the specified byte channel and driven by the given I/O loop.
protected	MessageBuffer(ByteChannel ch, IOLoop<M,?> loop, SSLContext sslContext) Creates a message buffer backed by the specified byte channel and driven by the given I/O loop.

Method Summary

Methods

Modifier and Type	Method and Description
boolean	alreadyDiscarded() Returns true if this buffer has already been discarded.
List<M>	dequeue() Gets a list of messages from the buffer in non-blocking fashion.
void	discard() Discards the message buffer.
void	flush() Flushes any pending writes accumulated in the out-bound buffer to the backing socket channel.
boolean	flushFailed() Returns true if a prior flush encountered an error.
protected abstract M	get(ByteBuffer rb) Gets a single message from the supplied byte buffer.
Exception	getFlushError() Gets the prior flush error, if one occurred.
protected ByteBuffer	growBuffer(ByteBuffer buffer) Grows the given buffer by growthFactor() and returns a new buffer instance with any remaining data copied into it.
protected double	growthFactor() Returns the out-bound buffer growth-factor.
ThroughputTracker	inBytes() Returns the in-bound bytes throughput tracker.
ThroughputTracker	inMessages() Returns the in-bound messages throughput tracker.
SelectionKey	key() Returns the selection key used for registration of the backing socket channel.
IOLoop<M,?>	loop() Returns the IO loop to which this stream is bound.
protected int	maxAge() Returns the maximum age before buffer is considered stale without any dequeue/queue operations.
ThroughputTracker	outBytes() Returns the out-bound bytes throughput tracker.
ThroughputTracker	outMessages() Returns the out-bound messages throughput tracker.
protected abstract void	put(M message, ByteBuffer wb) Puts the specified message into the internal buffer.
void	queue(List<M> messages) Queues the list of messages to the buffer and flushes to the backing channel if necessary.
void	queue(M message) Queues the message to the buffer and flushes to the backing channel if necessary.
void	setKey(SelectionKey key) Sets the select key obtained when the backing channel of this stream was registered with the IO loop selector.

Methods inherited from class java.lang.Object

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

Field Detail

log

protected org.slf4j.Logger log

Shared logger.

BUFFER_SIZE

protected static final int BUFFER_SIZE

Initial buffer size for in-bound & out-bound byte buffers.

See Also:

Constant Field Values

GROWTH_FACTOR

protected static final double GROWTH_FACTOR

Default growth factor for the out-bound byte buffer.

See Also:

Constant Field Values

MAX_AGE

protected static final int MAX_AGE

Default maximum age in milliseconds before the buffer becomes stale.

See Also:

Constant Field Values

Constructor Detail

MessageBuffer

protected MessageBuffer(ByteChannel ch,
             IOLoop<M,?> loop)

Creates a message buffer backed by the specified byte channel and driven by the given I/O loop.

Parameters:

ch - backing socket channel

loop - driver IO loop

MessageBuffer

protected MessageBuffer(ByteChannel ch,
             IOLoop<M,?> loop,
             SSLContext sslContext)

Creates a message buffer backed by the specified byte channel and driven by the given I/O loop.

Parameters:

ch - backing socket channel

loop - driver IO loop

sslContext - TLS secure context

Method Detail

alreadyDiscarded

public boolean alreadyDiscarded()

Returns true if this buffer has already been discarded. That is, discard() has been called.

Returns:

true if this buffer has been discarded

discard

public void discard()

Discards the message buffer. This involves freezing all throughput trackers, closing the backing channel and unregistering it from the driver loop.

setKey

public void setKey(SelectionKey key)

Sets the select key obtained when the backing channel of this stream was registered with the IO loop selector.

Parameters:

key - select key from registration of the backing channel

get

protected abstract M get(ByteBuffer rb)

Gets a single message from the supplied byte buffer.

Implementations are expected not to flip, reset or clear the buffer.

Parameters:

rb - read byte buffer

Returns:

read message or null if message could not be extracted due to insufficient available bytes

put

protected abstract void put(M message,
       ByteBuffer wb)

Puts the specified message into the internal buffer.

Implementations are expected not to flip, reset or clear the buffer.

Parameters:

message - message to be placed to the buffer

wb - write byte buffer

dequeue

public List<M> dequeue()
                                throws IOException

Gets a list of messages from the buffer in non-blocking fashion. If there are no messages to be read, the list will be empty. If the backing socket channel has been closed, null will be returned.

Returns:

list of read messages; null if backing channel is closed

Throws:

IOException - if data could not be read

queue

public void queue(List<M> messages)
           throws IOException

Queues the list of messages to the buffer and flushes to the backing channel if necessary.

Parameters:

messages - list of messages to be transfered

Throws:

IOException - if data could not be transfered or flushed

queue

public void queue(M message)
           throws IOException

Queues the message to the buffer and flushes to the backing channel if necessary.

Parameters:

message - message to be transfered

Throws:

IOException - if data could not be transfered or flushed

flush

public void flush()
           throws IOException

Flushes any pending writes accumulated in the out-bound buffer to the backing socket channel.

Throws:

IOException - if flush failed

flushFailed

public boolean flushFailed()

Returns true if a prior flush encountered an error. The error can be retrieved via getFlushError() method.

Returns:

true if a write failed

getFlushError

public Exception getFlushError()

Gets the prior flush error, if one occurred.

Returns:

flush error; null if none occurred

loop

public IOLoop<M,?> loop()

Returns the IO loop to which this stream is bound.

Returns:

I/O loop used to drive this stream

key

public SelectionKey key()

Returns the selection key used for registration of the backing socket channel.

Returns:

socket channel registration selection key

growBuffer

protected ByteBuffer growBuffer(ByteBuffer buffer)

Grows the given buffer by growthFactor() and returns a new buffer instance with any remaining data copied into it.

Parameters:

buffer - the buffer to grow

Returns:

a new (bigger) buffer instance

growthFactor

protected double growthFactor()

Returns the out-bound buffer growth-factor.

Returns:

growth factor; must be larger than 1.0

maxAge

protected int maxAge()

Returns the maximum age before buffer is considered stale without any dequeue/queue operations.

Returns:

max age in milliseconds; must be greater than 1

inMessages

public ThroughputTracker inMessages()

Returns the in-bound messages throughput tracker.

Returns:

throughput tracker

inBytes

public ThroughputTracker inBytes()

Returns the in-bound bytes throughput tracker.

Returns:

throughput tracker

outMessages

public ThroughputTracker outMessages()

Returns the out-bound messages throughput tracker.

Returns:

throughput tracker

outBytes

public ThroughputTracker outBytes()

Returns the out-bound bytes throughput tracker.

Returns:

throughput tracker