Package org.jgroups.blocks

Class MessageDispatcher

java.lang.Object
org.jgroups.blocks.MessageDispatcher
All Implemented Interfaces:
RequestHandler
Direct Known Subclasses:
RpcDispatcher
public class MessageDispatcher extends Object implements RequestHandler
Provides synchronous and asynchronous message sending with request-response correlation; i.e., matching responses with the original request. It also offers push-style message reception (by internally using the PullPushAdapter).

Channels are simple patterns to asynchronously send a receive messages. However, a significant number of communication patterns in group communication require synchronous communication. For example, a sender would like to send a message to the group and wait for all responses. Or another application would like to send a message to the group and wait only until the majority of the receivers have sent a response, or until a timeout occurred. MessageDispatcher offers a combination of the above pattern with other patterns.

Used on top of channel to implement group requests. Client's handle() method is called when request is received. Is the equivalent of RpcProtocol on the application instead of protocol level.

Version:
$Id: MessageDispatcher.java,v 1.74.2.5 2008/12/05 14:49:54 belaban Exp $
Author:
Bela Ban

  • Field Details

    • channel

      protected Channel channel

    • corr

      protected RequestCorrelator corr

    • msg_listener

      protected MessageListener msg_listener

    • membership_listener

      protected MembershipListener membership_listener

    • req_handler

      protected RequestHandler req_handler

    • prot_adapter

      protected org.jgroups.blocks.MessageDispatcher.ProtocolAdapter prot_adapter

    • transport_adapter

      protected org.jgroups.blocks.MessageDispatcher.TransportAdapter transport_adapter

    • members

      protected final Collection members

    • local_addr

      protected Address local_addr

    • deadlock_detection

      protected boolean deadlock_detection

    • adapter

      protected PullPushAdapter adapter

    • handler

      protected org.jgroups.blocks.MessageDispatcher.PullPushHandler handler

    • id

      protected Serializable id

    • log

      protected final org.apache.commons.logging.Log log

    • concurrent_processing

      protected boolean concurrent_processing
      Process items on the queue concurrently (RequestCorrelator). The default is to wait until the processing of an item has completed before fetching the next item from the queue. Note that setting this to true may destroy the properties of a protocol stack, e.g total or causal order may not be guaranteed. Set this to true only if you know what you're doing !

  • Constructor Details

  • Method Details

    • getMembers

      protected Collection getMembers()
      Returns a copy of members

    • getDeadlockDetection

      public boolean getDeadlockDetection()

    • setDeadlockDetection

      public void setDeadlockDetection(boolean flag)

    • getConcurrentProcessing

      public boolean getConcurrentProcessing()

    • setConcurrentProcessing

      public void setConcurrentProcessing(boolean flag)

    • start

      public final void start()

    • correlatorStarted

      protected void correlatorStarted()

    • stop

      public void stop()

    • setMessageListener

      public final void setMessageListener(MessageListener l)

    • getMessageListener

      public MessageListener getMessageListener()
      Gives access to the currently configured MessageListener. Returns null if there is no configured MessageListener.

    • setMembershipListener

      public final void setMembershipListener(MembershipListener l)

    • setRequestHandler

      public final void setRequestHandler(RequestHandler rh)

    • getChannel

      public Channel getChannel()
      Offers access to the underlying Channel.
      Returns:
      a reference to the underlying Channel.

    • setChannel

      public void setChannel(Channel ch)

    • send

      public void send(Message msg) throws ChannelNotConnectedException, ChannelClosedException
      Throws:
      ChannelNotConnectedException
      ChannelClosedException

    • castMessage

      public RspList castMessage(Vector dests, Message msg, int mode, long timeout)

    • castMessage

      public RspList castMessage(Vector dests, Message msg, int mode, long timeout, boolean use_anycasting)
      Cast a message to all members, and wait for mode responses. The responses are returned in a response list, where each response is associated with its sender.

      Uses GroupRequest.

      Parameters:
      dests - The members to which the message is to be sent. If it is null, then the message is sent to all members
      msg - The message to be sent to n members
      mode - Defined in GroupRequest. The number of responses to wait for:
      1. GET_FIRST: return the first response received.
      2. GET_ALL: wait for all responses (minus the ones from suspected members)
      3. GET_MAJORITY: wait for a majority of all responses (relative to the grp size)
      4. GET_ABS_MAJORITY: wait for majority (absolute, computed once)
      5. GET_N: wait for n responses (may block if n > group size)
      6. GET_NONE: wait for no responses, return immediately (non-blocking)
      timeout - If 0: wait forever. Otherwise, wait for mode responses or timeout time.
      Returns:
      RspList A list of responses. Each response is an Object and associated to its sender.

    • castMessage

      public RspList castMessage(Vector dests, Message msg, int mode, long timeout, boolean use_anycasting, RspFilter filter)

    • castMessage

      public void castMessage(Vector dests, long req_id, Message msg, RspCollector coll)
      Multicast a message request to all members in dests and receive responses via the RspCollector interface. When done receiving the required number of responses, the caller has to call done(req_id) on the underlyinh RequestCorrelator, so that the resources allocated to that request can be freed.
      Parameters:
      dests - The list of members from which to receive responses. Null means all members
      req_id - The ID of the request. Used by the underlying RequestCorrelator to correlate responses with requests
      msg - The request to be sent
      coll - The sender needs to provide this interface to collect responses. Call will return immediately if this is null

    • done

      public void done(long req_id)

    • sendMessage

      public Object sendMessage(Message msg, int mode, long timeout) throws TimeoutException, SuspectedException
      Sends a message to a single member (destination = msg.dest) and returns the response. The message's destination must be non-zero !
      Throws:
      TimeoutException
      SuspectedException

    • handle

      public Object handle(Message msg)
      Specified by:
      handle in interface RequestHandler