Package org.jgroups.blocks

Class RequestCorrelator

java.lang.Object
org.jgroups.blocks.RequestCorrelator
Direct Known Subclasses:
MuxRequestCorrelator
public class RequestCorrelator extends Object
Framework to send requests and receive matching responses (matching on request ID). Multiple requests can be sent at a time. Whenever a response is received, the correct RspCollector is looked up (key = id) and its method receiveResponse() invoked. A caller may use done() to signal that no more responses are expected, and that the corresponding entry may be removed.

RequestCorrelator can be installed at both client and server sides, it can also switch roles dynamically; i.e., send a request and at the same time process an incoming request (when local delivery is enabled, this is actually the default).

Author:
Bela Ban

  • Field Details

    • transport

      protected Object transport
      The protocol layer to use to pass up/down messages. Can be either a Protocol or a Transport

    • requests

      protected final ConcurrentMap<Long,RspCollector> requests
      The table of pending requests (keys=Long (request IDs), values=RequestEntry)

    • request_handler

      protected RequestHandler request_handler
      The handler for the incoming requests. It is called from inside the dispatcher thread

    • marshaller

      protected RpcDispatcher.Marshaller2 marshaller
      Possibility for an external marshaller to marshal/unmarshal responses

    • id

      protected short id
      makes the instance unique (together with IDs)

    • local_addr

      protected Address local_addr
      The address of this group member

    • started

      protected boolean started

    • log

      protected static final Log log

  • Constructor Details

    • RequestCorrelator

      @Deprecated public RequestCorrelator(String name, Object transport, RequestHandler handler)
      Deprecated.
      Constructor. Uses transport to send messages. If handler is not null, all incoming requests will be dispatched to it (via handle(Message)).
      Parameters:
      name - Used to differentiate between different RequestCorrelators (e.g. in different protocol layers). Has to be unique if multiple request correlators are used.
      transport - Used to send/pass up requests. Can be either a Transport (only send() will be used then), or a Protocol (up_prot.up()/down_prot.down() will be used)
      handler - Request handler. Method handle(Message) will be called when a request is received.

    • RequestCorrelator

      @Deprecated public RequestCorrelator(String name, Object transport, RequestHandler handler, Address local_addr)
      Deprecated.

    • RequestCorrelator

      public RequestCorrelator(short id, Object transport, RequestHandler handler, Address local_addr)

    • RequestCorrelator

      public RequestCorrelator(Object transport, RequestHandler handler, Address local_addr)

    • RequestCorrelator

      @Deprecated public RequestCorrelator(String name, Object transport, RequestHandler handler, boolean deadlock_detection)
      Deprecated.
      Constructor. Uses transport to send messages. If handler is not null, all incoming requests will be dispatched to it (via handle(Message)).
      Parameters:
      name - Used to differentiate between different RequestCorrelators (e.g. in different protocol layers). Has to be unique if multiple request correlators are used.
      transport - Used to send/pass up requests. Can be either a Transport (only send() will be used then), or a Protocol (up_prot.up()/down_prot.down() will be used)
      handler - Request handler. Method handle(Message) will be called when a request is received.
      deadlock_detection - When enabled (true) recursive synchronous message calls will be detected and processed with higher priority in order to solve deadlocks. Slows down processing a little bit when enabled due to runtime checks involved.

    • RequestCorrelator

      @Deprecated public RequestCorrelator(String name, Object transport, RequestHandler handler, boolean deadlock_detection, boolean concurrent_processing)
      Deprecated.

    • RequestCorrelator

      @Deprecated public RequestCorrelator(String name, Object transport, RequestHandler handler, boolean deadlock_detection, Address local_addr)
      Deprecated.

    • RequestCorrelator

      @Deprecated public RequestCorrelator(String name, Object transport, RequestHandler handler, boolean deadlock_detection, Address local_addr, boolean concurrent_processing)
      Deprecated.

    • RequestCorrelator

      @Deprecated public RequestCorrelator(String name, Object transport, RequestHandler handler, Address local_addr, boolean concurrent_processing)
      Deprecated.

  • Method Details

    • setDeadlockDetection

      public void setDeadlockDetection(boolean flag)
      Deprecated.
      deadlock detection is not needed with a concurrent stack
      Switch the deadlock detection mechanism on/off
      Parameters:
      flag - the deadlock detection flag

    • setRequestHandler

      public void setRequestHandler(RequestHandler handler)

    • setConcurrentProcessing

      public void setConcurrentProcessing(boolean concurrent_processing)
      Deprecated.
      Not needed since the introduction of the concurrent stack
      Parameters:
      concurrent_processing -

    • sendRequest

      @Deprecated public void sendRequest(long id, Message msg, RspCollector coll) throws Exception
      Deprecated.
      Helper method for sendRequest(long,List,Message,RspCollector).
      Throws:
      Exception

    • getMarshaller

      public RpcDispatcher.Marshaller getMarshaller()

    • setMarshaller

      public void setMarshaller(RpcDispatcher.Marshaller marshaller)

    • sendRequest

      public void sendRequest(long id, List<Address> dest_mbrs, Message msg, RspCollector coll) throws Exception
      Throws:
      Exception

    • sendRequest

      public void sendRequest(long id, Collection<Address> dest_mbrs, Message msg, RspCollector coll, RequestOptions options) throws Exception
      Sends a request to a group. If no response collector is given, no responses are expected (making the call asynchronous)
      Parameters:
      id - The request ID. Must be unique for this JVM (e.g. current time in millisecs)
      dest_mbrs - The list of members who should receive the call. Usually a group RPC is sent via multicast, but a receiver drops the request if its own address is not in this list. Will not be used if it is null.
      msg - The request to be sent. The body of the message carries the request data
      coll - A response collector (usually the object that invokes this method). Its methods receiveResponse() and suspect() will be invoked when a message has been received or a member is suspected, respectively.
      Throws:
      Exception

    • sendUnicastRequest

      public void sendUnicastRequest(long id, Address target, Message msg, RspCollector coll) throws Exception
      Sends a request to a single destination
      Parameters:
      id -
      target -
      msg -
      coll -
      Throws:
      Exception

    • done

      public void done(long id)
      Used to signal that a certain request may be garbage collected as all responses have been received.

    • receive

      public boolean receive(Event evt)
      Callback.

      Called by the protocol below when a message has been received. The algorithm should test whether the message is destined for us and, if not, pass it up to the next layer. Otherwise, it should remove the header and check whether the message is a request or response. In the first case, the message will be delivered to the request handler registered (calling its handle() method), in the second case, the corresponding response collector is looked up and the message delivered.

      Parameters:
      evt - The event to be received
      Returns:
      Whether or not the event was consumed. If true, don't pass message up, else pass it up

    • start

      public final void start()

    • stop

      public void stop()

    • registerProbeHandler

      public void registerProbeHandler(TP transport)

    • unregisterProbeHandler

      public void unregisterProbeHandler(TP transport)

    • receiveSuspect

      public void receiveSuspect(Address mbr)
      Event.SUSPECT event received from a layer below.

      All response collectors currently registered will be notified that mbr may have crashed, so they won't wait for its response.

    • receiveView

      public void receiveView(View new_view)
      Event.VIEW_CHANGE event received from a layer below.

      Mark all responses from members that are not in new_view as NOT_RECEIVED.

    • receiveMessage

      public boolean receiveMessage(Message msg)
      Handles a message coming from a layer below
      Returns:
      true if the message was consumed, don't pass it further up, else false

    • getLocalAddress

      public Address getLocalAddress()

    • setLocalAddress

      public void setLocalAddress(Address local_addr)

    • handleRequest

      protected void handleRequest(Message req, RequestCorrelator.Header hdr)
      Handle a request msg for this correlator
      Parameters:
      req - the request msg

    • prepareResponse

      protected void prepareResponse(Message rsp)