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This artifact provides a single jar that contains all classes required to use remote EJB and JMS, including all dependencies. It is intended for use by those not using maven, maven users should just import the EJB and JMS BOM's instead (shaded JAR's cause lots of problems with maven, as it is very easy to inadvertently end up with different versions on classes on the class path).

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package org.jgroups.protocols;

import org.jgroups.Address;
import org.jgroups.Message;
import org.jgroups.annotations.MBean;
import org.jgroups.annotations.ManagedAttribute;
import org.jgroups.annotations.Property;
import org.jgroups.conf.AttributeType;
import org.jgroups.util.Credit;
import org.jgroups.util.NonBlockingCredit;

import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.locks.ReentrantLock;
import java.util.function.Consumer;

/**
 * Non-blocking alternative to {@link UFC}.

 * JIRA: https://issues.redhat.com/browse/JGRP-2172
 * @author Bela Ban
 * @since  4.0.4
 */
@MBean(description="Simple non-blocking flow control protocol based on a credit system")
public class UFC_NB extends UFC {
    @Property(description="Max number of bytes of all queued messages for a given destination. If a given destination " +
      "has no credits left and the message cannot be added to the queue because it is full, then the sender thread " +
      "will be blocked until there is again space available in the queue, or the protocol is stopped.",type=AttributeType.BYTES)
    protected int                     max_queue_size=10_000_000;
    protected final Consumer send_function=msg -> down_prot.down(msg);
    protected Future               credit_send_task;


    public int      getMaxQueueSize()      {return max_queue_size;}
    public UFC_NB   setMaxQueueSize(int s) {this.max_queue_size=s; return this;}

    @ManagedAttribute(description="The number of messages currently queued due to insufficient credit",type=AttributeType.SCALAR)
    public int getNumberOfQueuedMessages() {
        return sent.values().stream().map(c -> ((NonBlockingCredit)c).getQueuedMessages()).reduce(0, Integer::sum);
    }

    @ManagedAttribute(description="The total size of all currently queued messages for all destinations",type=AttributeType.BYTES)
    public int getQueuedSize() {
        return sent.values().stream().map(c -> ((NonBlockingCredit)c).getQueuedMessageSize()).reduce(0, Integer::sum);
    }

    @ManagedAttribute(description="The number of times messages have been queued due to insufficient credits",type=AttributeType.SCALAR)
    public int getNumberOfQueuings() {
        return sent.values().stream().map(c -> ((NonBlockingCredit)c).getEnqueuedMessages()).reduce(0, Integer::sum);
    }

    public boolean isQueuingTo(Address dest) {
        NonBlockingCredit cred=(NonBlockingCredit)sent.get(dest);
        return cred != null && cred.isQueuing();
    }

    public int getQueuedMessagesTo(Address dest) {
        NonBlockingCredit cred=(NonBlockingCredit)sent.get(dest);
        return cred != null? cred.getQueuedMessages() : 0;
    }

    public void start() throws Exception {
        super.start();
        if(max_block_time > 0) {
            credit_send_task=getTransport().getTimer()
              .scheduleWithFixedDelay(this::sendCreditRequestsIfNeeded, max_block_time, max_block_time, TimeUnit.MILLISECONDS);
        }
    }

    public void stop() {
        super.stop();
        if(credit_send_task != null)
            credit_send_task.cancel(true);
    }

    @Override protected Object handleDownMessage(Message msg, int length) {
        Address dest=msg.getDest();
        if(dest == null) { // 2nd line of defense, not really needed
            log.error("%s doesn't handle multicast messages; passing message down", getClass().getSimpleName());
            return down_prot.down(msg);
        }

        Credit cred=sent.get(dest);
        if(cred == null)
            return down_prot.down(msg);

        if(running) {
            if(cred.decrementIfEnoughCredits(msg, length, 0)) // timeout is ignored
                return down_prot.down(msg);
            if(cred.needToSendCreditRequest(max_block_time))
                sendCreditRequest(dest, Math.max(0, max_credits - cred.get()));
            return null; // msg was queued
        }
        return down_prot.down(msg);
    }

    protected  T createCredit(int initial_credits) {
        return (T)new NonBlockingCredit(initial_credits, max_queue_size, new ReentrantLock(true), send_function);
    }

    /** Checks the sent table: if some credits are in queueing mode and credits left are less than min_credits:
     *  send a credit request */
    protected void sendCreditRequestsIfNeeded() {
        sent.forEach((dest, c) -> {
            NonBlockingCredit cred=(NonBlockingCredit)c;
            if(cred.get() < min_credits && cred.isQueuing() && cred.needToSendCreditRequest(max_block_time)) {
                sendCreditRequest(dest, Math.max(0, max_credits - cred.get()));
            }
        });
    }

}