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:
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

  • Field Details

    • filter

      protected Pattern filter

  • Constructor Details

    • PersistentValve

      public PersistentValve()

  • Method Details

    • 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 IOException, ServletException
      Description copied from interface: Valve

      Perform request processing as required by this Valve.

      An individual Valve MAY perform the following actions, in the specified order:

      • Examine and/or modify the properties of the specified Request and Response.
      • Examine the properties of the specified Request, completely generate the corresponding Response, and return control to the caller.
      • Examine the properties of the specified Request and Response, wrap either or both of these objects to supplement their functionality, and pass them on.
      • If the corresponding Response was not generated (and control was not returned), call the next Valve in the pipeline (if there is one) by executing getNext().invoke().
      • Examine, but not modify, the properties of the resulting Response (which was created by a subsequently invoked Valve or Container).

      A Valve MUST NOT do any of the following things:

      • Change request properties that have already been used to direct the flow of processing control for this request (for instance, trying to change the virtual host to which a Request should be sent from a pipeline attached to a Host or Context in the standard implementation).
      • Create a completed Response AND pass this Request and Response on to the next Valve in the pipeline.
      • Consume bytes from the input stream associated with the Request, unless it is completely generating the response, or wrapping the request before passing it on.
      • Modify the HTTP headers included with the Response after the getNext().invoke() method has returned.
      • Perform any actions on the output stream associated with the specified Response after the getNext().invoke() method has returned.
      Parameters:
      request - The servlet request to be processed
      response - The servlet response to be created
      Throws:
      IOException - if an input/output error occurs, or is thrown by a subsequently invoked Valve, Filter, or Servlet
      ServletException - if a servlet error occurs, or is thrown by a subsequently invoked Valve, Filter, or Servlet

    • onSemaphoreNotAcquired

      protected void onSemaphoreNotAcquired(Request request, Response response) throws 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:
      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(String uri)

    • getFilter

      public String getFilter()

    • setFilter

      public void setFilter(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.