Package org.jgroups.blocks

Class MessageDispatcher

  • All Implemented Interfaces:
    RequestHandler
    Direct Known Subclasses:
    RpcDispatcher
    public class MessageDispatcher
extends java.lang.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 Detail

      • channel

        protected Channel channel

      • prot_adapter

        protected org.jgroups.blocks.MessageDispatcher.ProtocolAdapter prot_adapter

      • transport_adapter

        protected org.jgroups.blocks.MessageDispatcher.TransportAdapter transport_adapter

      • members

        protected final java.util.Collection members

      • local_addr

        protected Address local_addr

      • deadlock_detection

        protected boolean deadlock_detection

      • handler

        protected org.jgroups.blocks.MessageDispatcher.PullPushHandler handler

      • id

        protected java.io.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 !

    • Method Detail

      • getMembers

        protected java.util.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)

      • castMessage

        public RspList castMessage​(java.util.Vector dests,
                           Message msg,
                           int mode,
                           long timeout)

      • castMessage

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

      • castMessage

        public void castMessage​(java.util.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)