org.apache.camel.processor

Class Throttler

java.lang.Object

org.apache.camel.support.ServiceSupport

org.apache.camel.processor.DelegateAsyncProcessor

org.apache.camel.processor.Throttler

All Implemented Interfaces:

AsyncProcessor, DelegateProcessor, Navigate<Processor>, Processor, Service, ShutdownableService, HasId, IdAware, StatefulService, SuspendableService, Traceable

public class Throttler
extends DelegateAsyncProcessor
implements Traceable, IdAware

A Throttler will set a limit on the maximum number of message exchanges which can be sent to a processor within a specific time period.

This pattern can be extremely useful if you have some external system which meters access; such as only allowing 100 requests per second; or if huge load can cause a particular system to malfunction or to reduce its throughput you might want to introduce some throttling. This throttle implementation is thread-safe and is therefore safe to be used by multiple concurrent threads in a single route. The throttling mechanism is a DelayQueue with maxRequestsPerPeriod permits on it. Each permit is set to be delayed by timePeriodMillis (except when the throttler is initialized or the throttle rate increased, then there is no delay for those permits). Callers trying to acquire a permit from the DelayQueue will block if necessary. The end result is a rolling window of time. Where from the callers point of view in the last timePeriodMillis no more than maxRequestsPerPeriod have been allowed to be acquired.

Version:

Field Summary

Fields inherited from class org.apache.camel.processor.DelegateAsyncProcessor

processor

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

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

Constructor Summary

Constructors

Constructor and Description
Throttler(CamelContext camelContext, Processor processor, Expression maxRequestsPerPeriodExpression, long timePeriodMillis, ExecutorService asyncExecutor, boolean shutdownAsyncExecutor, boolean rejectExecution)

Method Summary

Modifier and Type	Method and Description
protected void	calculateAndSetMaxRequestsPerPeriod(Exchange exchange) Evaluates the maxRequestsPerPeriodExpression and adjusts the throttle rate up or down.
protected void	doShutdown() Implementations override this method to perform customized shutdown.
protected void	doStart() Implementations override this method to support customized start/stop.
protected void	enqueuePermit(org.apache.camel.processor.Throttler.ThrottlePermit permit, Exchange exchange) Returns a permit to the DelayQueue, first resetting it's delay to be relative to now.
int	getCurrentMaximumRequestsPerPeriod() Gets the current maximum request per period value.
String	getId() Returns the id
Expression	getMaximumRequestsPerPeriodExpression()
long	getTimePeriodMillis()
String	getTraceLabel() Gets the trace label used for logging when tracing is enabled.
boolean	isAsyncDelayed()
boolean	isCallerRunsWhenRejected()
boolean	isRejectExecution()
boolean	process(Exchange exchange, AsyncCallback callback) Processes the message exchange.
protected boolean	processAsynchronously(Exchange exchange, AsyncCallback callback) Delegate blocking on the DelayQueue to an asyncExecutor.
void	setAsyncDelayed(boolean asyncDelayed)
void	setCallerRunsWhenRejected(boolean callerRunsWhenRejected)
void	setId(String id) Sets the id
void	setMaximumRequestsPerPeriodExpression(Expression maxRequestsPerPeriodExpression) Sets the maximum number of requests per time period expression
void	setRejectExecution(boolean rejectExecution)
void	setTimePeriodMillis(long timePeriodMillis) Sets the time period during which the maximum number of requests apply
String	toString()

Methods inherited from class org.apache.camel.processor.DelegateAsyncProcessor

doStop, getProcessor, hasNext, next, process, processNext, setProcessor, setProcessor

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

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

Methods inherited from class java.lang.Object

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

Constructor Detail

Throttler

public Throttler(CamelContext camelContext,
                 Processor processor,
                 Expression maxRequestsPerPeriodExpression,
                 long timePeriodMillis,
                 ExecutorService asyncExecutor,
                 boolean shutdownAsyncExecutor,
                 boolean rejectExecution)

Method Detail

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

Overrides:

process in class DelegateAsyncProcessor

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

processAsynchronously

protected boolean processAsynchronously(Exchange exchange,
                                        AsyncCallback callback)

Delegate blocking on the DelayQueue to an asyncExecutor. Except if the executor rejects the submission and isCallerRunsWhenRejected() is enabled, then this method will delegate back to process(), but not before changing the exchange state to stop any recursion.

enqueuePermit

protected void enqueuePermit(org.apache.camel.processor.Throttler.ThrottlePermit permit,
                             Exchange exchange)

Returns a permit to the DelayQueue, first resetting it's delay to be relative to now.

calculateAndSetMaxRequestsPerPeriod

protected void calculateAndSetMaxRequestsPerPeriod(Exchange exchange)
                                            throws Exception

Evaluates the maxRequestsPerPeriodExpression and adjusts the throttle rate up or down.

Throws:

Exception

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.

Overrides:

doStart in class DelegateAsyncProcessor

Throws:

Exception

See Also:

ServiceSupport.doStop()

doShutdown

protected void doShutdown()
                   throws Exception

Description copied from class: ServiceSupport

Implementations override this method to perform customized shutdown.

Overrides:

doShutdown in class DelegateAsyncProcessor

Throws:

Exception

isRejectExecution

public boolean isRejectExecution()

setRejectExecution

public void setRejectExecution(boolean rejectExecution)

isAsyncDelayed

public boolean isAsyncDelayed()

setAsyncDelayed

public void setAsyncDelayed(boolean asyncDelayed)

isCallerRunsWhenRejected

public boolean isCallerRunsWhenRejected()

setCallerRunsWhenRejected

public void setCallerRunsWhenRejected(boolean callerRunsWhenRejected)

getId

public String getId()

Description copied from interface: HasId

Returns the id

Specified by:

getId in interface HasId

Returns:

the id

setId

public void setId(String id)

Description copied from interface: IdAware

Sets the id

Specified by:

setId in interface IdAware

Parameters:

id - the id

setMaximumRequestsPerPeriodExpression

public void setMaximumRequestsPerPeriodExpression(Expression maxRequestsPerPeriodExpression)

Sets the maximum number of requests per time period expression

getMaximumRequestsPerPeriodExpression

public Expression getMaximumRequestsPerPeriodExpression()

getCurrentMaximumRequestsPerPeriod

public int getCurrentMaximumRequestsPerPeriod()

Gets the current maximum request per period value.

setTimePeriodMillis

public void setTimePeriodMillis(long timePeriodMillis)

Sets the time period during which the maximum number of requests apply

getTimePeriodMillis

public long getTimePeriodMillis()

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

toString

public String toString()

Overrides:

toString in class DelegateAsyncProcessor