org.apache.catalina.valves

Class PersistentValve

java.lang.Object

org.apache.catalina.util.LifecycleBase

org.apache.catalina.util.LifecycleMBeanBase

org.apache.catalina.valves.ValveBase

org.apache.catalina.valves.PersistentValve

All Implemented Interfaces:

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

public class PersistentValve
extends ValveBase

Valve that implements per-request session persistence. It is intended to be used with non-sticky load-balancers and a PersistentManager. The Valve works by loading the session from the Store at the start of the request, the request then updates the session as required and the Valve saves the session to the Store at the end of the request.

To avoid conflicts and/or errors when updating the session store, each session must only be accessed by no more than one concurrent request. The filter field can be used to define requests (e.g. those for static resources) that do not need access to the session and can Requests for resources that do not need to access the session and can bypass the session load/save functionality provided by this Valve.

The Valve uses a per session Semaphore to ensure that each session is accessed by no more than one request at a time within a single Tomcat instance. The behaviour if multiple requests try to access the session concurrently can be controlled by the semaphoreFairness, semaphoreBlockOnAcquire and semaphoreAcquireUninterruptibly fields. If a request fails to obtain the Semaphore, the response is generated by the onSemaphoreNotAcquired(Request, Response) method which, by default, returns a 429 status code.

The per session Semaphores only provide limited protection against concurrent requests within a single Tomcat instance. If multiple requests access the same session concurrently across different Tomcat instances, update conflicts and/or session data loss and/or errors are very likely.

USAGE CONSTRAINTS:

• This Valve must only be used with a PersistentManager
• The client must ensure that no more than one concurrent request accesses a session at any time across all Tomcat instances

Nested Class Summary

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

Lifecycle.SingleUse

Field Summary

Fields

Modifier and Type	Field and Description
protected java.util.regex.Pattern	filter

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

asyncSupported, container, containerLog, next, sm

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

mserver

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 and Description
PersistentValve()

Method Summary

Modifier and Type	Method and Description
java.lang.String	getFilter()
void	invoke(Request request, Response response) Select the appropriate child Context to process this request, based on the specified request URI.
protected boolean	isRequestWithoutSession(java.lang.String uri)
boolean	isSemaphoreAcquireUninterruptibly() If a thread is blocking to acquire a per session Semaphore, can that thread be interrupted?
boolean	isSemaphoreBlockOnAcquire() If a thread attempts to acquire the per session Semaphore while it is being used by another request, should the thread block to wait for the Semaphore or should the request be rejected?
boolean	isSemaphoreFairness() If multiple threads attempt to acquire the same per session Semaphore, will permits be granted in the same order they were requested?
protected boolean	isSessionStale(Session session, long timeNow) Indicate whether the session has been idle for longer than its expiration date as of the supplied time.
protected void	onSemaphoreNotAcquired(Request request, Response response) Handle the case where a semaphore cannot be obtained.
void	setContainer(Container container) Set the Container with which this instance is associated.
void	setFilter(java.lang.String filter)
void	setSemaphoreAcquireUninterruptibly(boolean semaphoreAcquireUninterruptibly) Configure whether a thread blocking to acquire a per session Semaphore can be interrupted.
void	setSemaphoreBlockOnAcquire(boolean semaphoreBlockOnAcquire) Configure whether a thread should block and wait for the per session Semaphore or reject the request if the Semaphore is being used by another request.
void	setSemaphoreFairness(boolean semaphoreFairness) Configure whether the per session Semaphores will handle granting of permits in the same order they were requested if multiple threads attempt to acquire the same Semaphore.

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

backgroundProcess, getContainer, getDomainInternal, getNext, getObjectNameKeyProperties, initInternal, isAsyncSupported, setAsyncSupported, setNext, startInternal, stopInternal, 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

filter

protected java.util.regex.Pattern filter

Constructor Detail

PersistentValve

public PersistentValve()

Method Detail

setContainer

public void setContainer(Container container)

Description copied from interface: Contained

Set the Container with which this instance is associated.

Specified by:

setContainer in interface Contained

Overrides:

setContainer in class ValveBase

Parameters:

container - The Container instance with which this instance is to be associated, or null to disassociate this instance from any Container

invoke

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

Select the appropriate child Context to process this request, based on the specified request URI. If no matching Context can be found, return an appropriate HTTP error.

Parameters:

request - Request to be processed

response - Response to be produced

Throws:

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

ServletException - if a servlet error occurred

onSemaphoreNotAcquired

protected void onSemaphoreNotAcquired(Request request,
                                      Response response)
                               throws java.io.IOException

Handle the case where a semaphore cannot be obtained. The default behaviour is to return a 429 (too many requests) status code.

Parameters:

request - The request that will not be processed

response - The response that will be used for this request

Throws:

java.io.IOException - If an I/O error occurs while working with the request or response

isSessionStale

protected boolean isSessionStale(Session session,
                                 long timeNow)

Indicate whether the session has been idle for longer than its expiration date as of the supplied time.

Parameters:

session - The session to check

timeNow - The current time to check for

Returns:

true if the session is past its expiration

isRequestWithoutSession

protected boolean isRequestWithoutSession(java.lang.String uri)

getFilter

public java.lang.String getFilter()

setFilter

public void setFilter(java.lang.String filter)

isSemaphoreFairness

public boolean isSemaphoreFairness()

If multiple threads attempt to acquire the same per session Semaphore, will permits be granted in the same order they were requested?

Returns:

true if fairness is enabled, otherwise false

setSemaphoreFairness

public void setSemaphoreFairness(boolean semaphoreFairness)

Configure whether the per session Semaphores will handle granting of permits in the same order they were requested if multiple threads attempt to acquire the same Semaphore.

Parameters:

semaphoreFairness - true if permits should be granted in the same order they are requested, otherwise false

isSemaphoreBlockOnAcquire

public boolean isSemaphoreBlockOnAcquire()

If a thread attempts to acquire the per session Semaphore while it is being used by another request, should the thread block to wait for the Semaphore or should the request be rejected?

Returns:

true if the thread should block, otherwise false to reject the concurrent request

setSemaphoreBlockOnAcquire

public void setSemaphoreBlockOnAcquire(boolean semaphoreBlockOnAcquire)

Configure whether a thread should block and wait for the per session Semaphore or reject the request if the Semaphore is being used by another request.

Parameters:

semaphoreBlockOnAcquire - true to block, otherwise false

isSemaphoreAcquireUninterruptibly

public boolean isSemaphoreAcquireUninterruptibly()

If a thread is blocking to acquire a per session Semaphore, can that thread be interrupted?

Returns:

true if the thread can not be interrupted, otherwise false.

setSemaphoreAcquireUninterruptibly

public void setSemaphoreAcquireUninterruptibly(boolean semaphoreAcquireUninterruptibly)

Configure whether a thread blocking to acquire a per session Semaphore can be interrupted.

Parameters:

semaphoreAcquireUninterruptibly - true if the thread can not be interrupted, otherwise false.