Examples of org.jgroups.util.Digest

org.jgroups.util.Digest
A message digest, which is used by the PBCAST layer for gossiping (also used by NAKACK for keeping track of current seqnos for all members). It contains pairs of senders and a range of seqnos (low and high), where each sender is associated with its highest and lowest seqnos seen so far. That is, the lowest seqno which was not yet garbage-collected and the highest that was seen so far and is deliverable (or was already delivered) to the application. A range of [0 - 0] means no messages have been received yet.
April 3 2001 (bela): Added high_seqnos_seen member. It is used to disseminate information about the last (highest) message M received from a sender P. Since we might be using a negative acknowledgment message numbering scheme, we would never know if the last message was lost. Therefore we periodically gossip and include the last message seqno. Members who haven't seen it (e.g. because msg was dropped) will request a retransmission. See DESIGN for details. @author Bela Ban

                                                                             bind_addr, bind_port));
            Thread t = getThreadFactory().newThread(spawner, "STREAMING_STATE_TRANSFER server socket acceptor");
            t.start();
        }


        Digest digest = isDigestNeeded() ? (Digest) down_prot.down(Event.GET_DIGEST_EVT) : null;


        Message state_rsp = new Message(stateRequester);
        StateHeader hdr = new StateHeader(StateHeader.STATE_RSP, local_addr, use_default_transport
                ? null
                : spawner.getServerSocketAddress(), digest, id);

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                down_prot.down(new Event(Event.OPEN_BARRIER));
        }
    }


    void handleStateRsp(final StateHeader hdr) {
        Digest tmp_digest = hdr.my_digest;
        if (isDigestNeeded()) {
            if (tmp_digest == null) {
                if (log.isWarnEnabled())
                    log.warn("digest received from " + hdr.sender
                            + " is null, skipping setting digest !");

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    }






    void becomeSingletonMember(Address mbr) {
        Digest initial_digest;
        ViewId view_id;
        Vector<Address> mbrs=new Vector<Address>(1);


        // set the initial digest (since I'm the first member)
        initial_digest=new Digest(gms.local_addr, 0, 0); // initial seqno mcast by me will be 1 (highest seen +1)
        gms.setDigest(initial_digest);


        view_id=new ViewId(mbr);       // create singleton view with mbr as only member
        mbrs.addElement(mbr);

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            // Example: {A}, B joins, after returning JoinRsp to B, A garbage collects messages higher than those
            // in the digest returned to the client, so the client will *not* be able to ask for retransmission
            // of those messages if he misses them            
            if(hasJoiningMembers) {
                gms.getDownProtocol().down(new Event(Event.SUSPEND_STABLE, MAX_SUSPEND_TIMEOUT));
                Digest tmp=gms.getDigest(); // get existing digest
                MutableDigest join_digest=null;
                if(tmp == null){
                    log.error("received null digest from GET_DIGEST: will cause JOIN to fail");
                }
                else {
                    // create a new digest, which contains the new member
                    join_digest=new MutableDigest(tmp.size() + new_mbrs.size());
                    join_digest.add(tmp); // add the existing digest to the new one
                    for(Address member:new_mbrs)
                        join_digest.add(member, 0, 0); // ... and add the new members. their first seqno will be 1
                }
                join_rsp=new JoinRsp(new_view, join_digest != null? join_digest.copy() : null);

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    private static String dumpDigests(JChannel ... channels) {
        StringBuilder sb=new StringBuilder();
        for(JChannel ch: channels) {
            sb.append(ch.getAddress()).append(": ");
            NAKACK nakack=(NAKACK)ch.getProtocolStack().findProtocol(NAKACK.class);
            Digest digest=nakack.getDigest();
            sb.append(digest).append("\n");
        }
        return sb.toString();
    }

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            finally {
                received.unlock();
            }


            if(send_stable_msg) {
                Digest my_digest=getDigest();  // asks the NAKACK protocol for the current digest,
                if(log.isTraceEnabled())
                    log.trace("setting latest_local_digest from NAKACK: " + my_digest.printHighestDeliveredSeqnos());
                sendStableMessage(my_digest);
            }
        }
    }

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    }




    @ManagedOperation
    public void runMessageGarbageCollection() {
        Digest copy=getDigest();
        sendStableMessage(copy);
    }

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    }




    @GuardedBy("lock")
    private void resetDigest() {
        Digest tmp=getDigest();
        digest.replace(tmp);
        if(log.isTraceEnabled())
            log.trace(local_addr + ": resetting digest from NAKACK: " + digest.printHighestDeliveredSeqnos());
        votes.clear();
    }

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            if(log.isTraceEnabled())
                log.trace("STABLE message will not be handled as I'm suspended");
            return;
        }


        Digest copy=null;
        lock.lock();
        try {
            if(votes.contains(sender))  // already received gossip from sender; discard it
                return;
            num_stable_msgs_received++;

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                    log.trace("stable task will not run as suspended=" + suspended);
                return;
            }


            // asks the NAKACK protocol for the current digest
            Digest my_digest=getDigest();
            if(my_digest == null) {
                if(log.isWarnEnabled())
                    log.warn("received null digest, skipped sending of stable message");
                return;
            }
            if(log.isTraceEnabled())
                log.trace(local_addr + ": setting latest_local_digest from NAKACK: " + my_digest.printHighestDeliveredSeqnos());
            sendStableMessage(my_digest);
        }

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Related Classes of org.jgroups.util.Digest

org.jgroups.Address

org.jgroups.protocols.GMS_MergeTest

org.jgroups.protocols.pbcast.ClientGmsImpl

org.jgroups.protocols.pbcast.CoordGmsImpl

org.jgroups.protocols.pbcast.FLUSH

org.jgroups.protocols.pbcast.JoinRsp

org.jgroups.protocols.pbcast.NAKACK

org.jgroups.protocols.pbcast.ParticipantGmsImpl

org.jgroups.protocols.pbcast.STABLE

org.jgroups.protocols.pbcast.STABLE$StableHeader

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