Package org.apache.catalina.valves

Class SemaphoreValve

java.lang.Object

org.apache.catalina.util.LifecycleBase

org.apache.catalina.util.LifecycleMBeanBase

org.apache.catalina.valves.ValveBase

org.apache.catalina.valves.SemaphoreValve

All Implemented Interfaces:

javax.management.MBeanRegistration, Contained, JmxEnabled, Lifecycle, Valve

public class SemaphoreValve
extends ValveBase

Implementation of a Valve that limits concurrency.

This Valve may be attached to any Container, depending on the granularity of the concurrency control you wish to perform. Note that internally, some async requests may require multiple serial requests to complete what - to the user - appears as a single request.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.catalina.Lifecycle

Lifecycle.SingleUse

Field Summary

Fields

Modifier and Type	Field	Description
protected boolean	block	Block until a permit is available.
protected int	concurrency	Concurrency level of the semaphore.
protected boolean	fairness	Fairness of the semaphore.
protected int	highConcurrencyStatus	High concurrency status.
protected boolean	interruptible	Block interruptibly until a permit is available.
protected java.util.concurrent.Semaphore	semaphore	Semaphore.

Fields inherited from class org.apache.catalina.valves.ValveBase

asyncSupported, container, containerLog, next, sm

Fields inherited from interface org.apache.catalina.Lifecycle

AFTER_DESTROY_EVENT, AFTER_INIT_EVENT, AFTER_START_EVENT, AFTER_STOP_EVENT, BEFORE_DESTROY_EVENT, BEFORE_INIT_EVENT, BEFORE_START_EVENT, BEFORE_STOP_EVENT, CONFIGURE_START_EVENT, CONFIGURE_STOP_EVENT, PERIODIC_EVENT, START_EVENT, STOP_EVENT

Constructor Summary

Constructors

Constructor	Description
SemaphoreValve()	Construct a new SemaphoreValve with async support enabled.

Method Summary

Modifier and Type	Method	Description
boolean	controlConcurrency(Request request, Response response)	Subclass friendly method to add conditions.
boolean	getBlock()	Return whether the valve blocks until a permit is available.
int	getConcurrency()	Return the concurrency level of the semaphore.
boolean	getFairness()	Return the fairness setting of the semaphore.
int	getHighConcurrencyStatus()	Return the HTTP status code returned when concurrency is too high.
boolean	getInterruptible()	Return whether the valve blocks interruptibly.
void	invoke(Request request, Response response)	Do concurrency control on the request using the semaphore.
void	permitDenied(Request request, Response response)	Subclass friendly method to add error handling when a permit isn't granted.
void	setBlock(boolean block)	Set whether the valve blocks until a permit is available.
void	setConcurrency(int concurrency)	Set the concurrency level of the semaphore.
void	setFairness(boolean fairness)	Set the fairness setting of the semaphore.
void	setHighConcurrencyStatus(int highConcurrencyStatus)	Set the HTTP status code returned when concurrency is too high.
void	setInterruptible(boolean interruptible)	Set whether the valve blocks interruptibly.
protected void	startInternal()	Start this component and implement the requirements of LifecycleBase.startInternal().
protected void	stopInternal()	Stop this component and implement the requirements of LifecycleBase.stopInternal().

Methods inherited from class org.apache.catalina.valves.ValveBase

backgroundProcess, getContainer, getDomainInternal, getNext, getObjectNameKeyProperties, initInternal, isAsyncSupported, setAsyncSupported, setContainer, setNext, toString

Methods inherited from class org.apache.catalina.util.LifecycleMBeanBase

destroyInternal, getDomain, getObjectName, postDeregister, postRegister, preDeregister, preRegister, register, setDomain, unregister, unregister

Methods inherited from class org.apache.catalina.util.LifecycleBase

addLifecycleListener, destroy, findLifecycleListeners, fireLifecycleEvent, getState, getStateName, getThrowOnFailure, init, removeLifecycleListener, setState, setState, setThrowOnFailure, start, stop

Methods inherited from class java.lang.Object

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

Field Detail

semaphore

protected java.util.concurrent.Semaphore semaphore

Semaphore.

concurrency

protected int concurrency

Concurrency level of the semaphore.

fairness

protected boolean fairness

Fairness of the semaphore.

block

protected boolean block

Block until a permit is available.

interruptible

protected boolean interruptible

Block interruptibly until a permit is available.

highConcurrencyStatus

protected int highConcurrencyStatus

High concurrency status. This status code is returned as an error if concurrency is too high.

Constructor Detail

SemaphoreValve

public SemaphoreValve()

Construct a new SemaphoreValve with async support enabled.

Method Detail

getConcurrency

public int getConcurrency()

Return the concurrency level of the semaphore.

Returns:

the concurrency level

setConcurrency

public void setConcurrency(int concurrency)

Set the concurrency level of the semaphore.

Parameters:

concurrency - the concurrency level

getFairness

public boolean getFairness()

Return the fairness setting of the semaphore.

Returns:

true if the semaphore uses fair ordering

setFairness

public void setFairness(boolean fairness)

Set the fairness setting of the semaphore.

Parameters:

fairness - true if the semaphore should use fair ordering

getBlock

public boolean getBlock()

Return whether the valve blocks until a permit is available.

Returns:

true if the valve blocks waiting for a permit

setBlock

public void setBlock(boolean block)

Set whether the valve blocks until a permit is available.

Parameters:

block - true if the valve should block waiting for a permit

getInterruptible

public boolean getInterruptible()

Return whether the valve blocks interruptibly.

Returns:

true if the valve blocks interruptibly

setInterruptible

public void setInterruptible(boolean interruptible)

Set whether the valve blocks interruptibly.

Parameters:

interruptible - true if the valve should block interruptibly

getHighConcurrencyStatus

public int getHighConcurrencyStatus()

Return the HTTP status code returned when concurrency is too high.

Returns:

the status code, or -1 if no error is returned

setHighConcurrencyStatus

public void setHighConcurrencyStatus(int highConcurrencyStatus)

Set the HTTP status code returned when concurrency is too high.

Parameters:

highConcurrencyStatus - the status code to return

startInternal

protected void startInternal()
                      throws LifecycleException

Start this component and implement the requirements of LifecycleBase.startInternal().

Overrides:

startInternal in class ValveBase

Throws:

LifecycleException - if this component detects a fatal error that prevents this component from being used

stopInternal

protected void stopInternal()
                     throws LifecycleException

Stop this component and implement the requirements of LifecycleBase.stopInternal().

Overrides:

stopInternal in class ValveBase

Throws:

LifecycleException - if this component detects a fatal error that prevents this component from being used

invoke

public void invoke(Request request,
                   Response response)
            throws java.io.IOException,
                   ServletException

Do concurrency control on the request using the semaphore.

Parameters:

request - The servlet request to be processed

response - The servlet response to be created

Throws:

java.io.IOException - if an input/output error occurs

ServletException - if a servlet error occurs

controlConcurrency

public boolean controlConcurrency(Request request,
                                  Response response)

Subclass friendly method to add conditions.

Parameters:

request - The Servlet request

response - The Servlet response

Returns:

true if the concurrency control should occur on this request

permitDenied

public void permitDenied(Request request,
                         Response response)
                  throws java.io.IOException,
                         ServletException

Subclass friendly method to add error handling when a permit isn't granted.

Parameters:

request - The Servlet request

response - The Servlet response

Throws:

java.io.IOException - Error writing output

ServletException - Other error