org.apache.camel.processor

Class StreamResequencer

java.lang.Object

org.apache.camel.support.ServiceSupport

org.apache.camel.processor.StreamResequencer

All Implemented Interfaces:

AsyncProcessor, Navigate<Processor>, Processor, SequenceSender<Exchange>, Service, ShutdownableService, StatefulService, SuspendableService, Traceable

public class StreamResequencer
extends ServiceSupport
implements SequenceSender<Exchange>, AsyncProcessor, Navigate<Processor>, Traceable

A resequencer that re-orders a (continuous) stream of Exchanges. The algorithm implemented by ResequencerEngine is based on the detection of gaps in a message stream rather than on a fixed batch size. Gap detection in combination with timeouts removes the constraint of having to know the number of messages of a sequence (i.e. the batch size) in advance.

Messages must contain a unique sequence number for which a predecessor and a successor is known. For example a message with the sequence number 3 has a predecessor message with the sequence number 2 and a successor message with the sequence number 4. The message sequence 2,3,5 has a gap because the successor of 3 is missing. The resequencer therefore has to retain message 5 until message 4 arrives (or a timeout occurs).

Instances of this class poll for Exchanges from a given endpoint. Resequencing work and the delivery of messages to the next processor is done within the single polling thread.

Version:

See Also:

ResequencerEngine

Field Summary

Fields inherited from class org.apache.camel.support.ServiceSupport

shutdown, shuttingdown, started, starting, stopped, stopping, suspended, suspending

Constructor Summary

Constructors

Constructor and Description
StreamResequencer(CamelContext camelContext, Processor processor, SequenceElementComparator<Exchange> comparator) Creates a new StreamResequencer instance.

Method Summary

Methods

Modifier and Type	Method and Description
protected void	doStart() Implementations override this method to support customized start/stop.
protected void	doStop() Implementations override this method to support customized start/stop.
int	getCapacity() Returns this resequencer's capacity.
ExceptionHandler	getExceptionHandler() Returns this resequencer's exception handler.
Processor	getProcessor() Returns the next processor.
long	getTimeout() Returns this resequencer's timeout.
String	getTraceLabel() Gets the trace label used for logging when tracing is enabled.
boolean	hasNext() Are there more outputs?
boolean	isIgnoreInvalidExchanges()
List<Processor>	next() Next group of outputs
void	process(Exchange exchange) Processes the message exchange
boolean	process(Exchange exchange, AsyncCallback callback) Processes the message exchange.
void	sendElement(Exchange exchange) Sends the exchange to the next processor.
void	setCapacity(int capacity)
void	setIgnoreInvalidExchanges(boolean ignoreInvalidExchanges) Sets whether to ignore invalid exchanges which cannot be used by this stream resequencer.
void	setRejectOld(Boolean rejectOld)
void	setTimeout(long timeout)
String	toString()

Methods inherited from class org.apache.camel.support.ServiceSupport

doResume, doShutdown, doSuspend, getStatus, getVersion, isRunAllowed, isStarted, isStarting, isStopped, isStopping, isStoppingOrStopped, isSuspended, isSuspending, resume, shutdown, start, stop, suspend

Methods inherited from class java.lang.Object

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

Constructor Detail

StreamResequencer

public StreamResequencer(CamelContext camelContext,
                 Processor processor,
                 SequenceElementComparator<Exchange> comparator)

Creates a new StreamResequencer instance.

Parameters:

processor - next processor that processes re-ordered exchanges.

comparator - a sequence element comparator for exchanges.

Method Detail

getExceptionHandler

public ExceptionHandler getExceptionHandler()

Returns this resequencer's exception handler.

getProcessor

public Processor getProcessor()

Returns the next processor.

getCapacity

public int getCapacity()

Returns this resequencer's capacity. The capacity is the maximum number of exchanges that can be managed by this resequencer at a given point in time. If the capacity if reached, polling from the endpoint will be skipped for timeout milliseconds giving exchanges the possibility to time out and to be delivered after the waiting period.

Returns:

this resequencer's capacity.

getTimeout

public long getTimeout()

Returns this resequencer's timeout. This sets the resequencer engine's timeout via ResequencerEngine.setTimeout(long). This value is also used to define the polling timeout from the endpoint.

Returns:

this resequencer's timeout. (Processor)

See Also:

ResequencerEngine.setTimeout(long)

setCapacity

public void setCapacity(int capacity)

setTimeout

public void setTimeout(long timeout)

isIgnoreInvalidExchanges

public boolean isIgnoreInvalidExchanges()

setRejectOld

public void setRejectOld(Boolean rejectOld)

setIgnoreInvalidExchanges

public void setIgnoreInvalidExchanges(boolean ignoreInvalidExchanges)

Sets whether to ignore invalid exchanges which cannot be used by this stream resequencer.

Default is false, by which an CamelExchangeException is thrown if the Exchange is invalid.

toString

public String toString()

Overrides:

toString in class Object

getTraceLabel

public String getTraceLabel()

Description copied from interface: Traceable

Gets the trace label used for logging when tracing is enabled.

The label should be short and precise.

Specified by:

getTraceLabel in interface Traceable

Returns:

the label

doStart

protected void doStart()
                throws Exception

Description copied from class: ServiceSupport

Implementations override this method to support customized start/stop.

Important: See ServiceSupport.doStop() for more details.

Specified by:

doStart in class ServiceSupport

Throws:

Exception

See Also:

ServiceSupport.doStop()

doStop

protected void doStop()
               throws Exception

Description copied from class: ServiceSupport

Implementations override this method to support customized start/stop.

Important: Camel will invoke this ServiceSupport.doStop() method when the service is being stopped. This method will also be invoked if the service is still in uninitialized state (eg has not been started). The method is always called to allow the service to do custom logic when the service is being stopped, such as when CamelContext is shutting down.

Specified by:

doStop in class ServiceSupport

Throws:

Exception

See Also:

ServiceSupport.doStart()

sendElement

public void sendElement(Exchange exchange)
                 throws Exception

Sends the exchange to the next processor.

Specified by:

sendElement in interface SequenceSender<Exchange>

Parameters:

exchange - exchange to send.

Throws:

Exception - if delivery fails.

process

public void process(Exchange exchange)
             throws Exception

Description copied from interface: Processor

Processes the message exchange

Specified by:

process in interface Processor

Parameters:

exchange - the message exchange

Throws:

Exception - if an internal processing error has occurred.

process

public boolean process(Exchange exchange,
              AsyncCallback callback)

Description copied from interface: AsyncProcessor

Processes the message exchange. Similar to Processor.process(org.apache.camel.Exchange), but the caller supports having the exchange asynchronously processed.

If there was a failure processing then the caused Exception would be set on the Exchange.

Specified by:

process in interface AsyncProcessor

Parameters:

exchange - the message exchange

callback - the AsyncCallback will be invoked when the processing of the exchange is completed. If the exchange is completed synchronously, then the callback is also invoked synchronously. The callback should therefore be careful of starting recursive loop.

Returns:

(doneSync) true to continue execute synchronously, false to continue being executed asynchronously

hasNext

public boolean hasNext()

Description copied from interface: Navigate

Are there more outputs?

Specified by:

hasNext in interface Navigate<Processor>

Returns:

true if more outputs

next

public List<Processor> next()

Description copied from interface: Navigate

Next group of outputs

Specified by:

next in interface Navigate<Processor>

Returns:

next group or null if no more outputs