org.jgroups.protocols.REVERSE Maven / Gradle / Ivy

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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.Message;
import org.jgroups.annotations.MBean;
import org.jgroups.annotations.ManagedAttribute;
import org.jgroups.annotations.ManagedOperation;
import org.jgroups.stack.Protocol;
import org.jgroups.util.MessageBatch;

import java.util.Deque;
import java.util.Iterator;
import java.util.concurrent.ConcurrentLinkedDeque;
import java.util.function.Predicate;

/**
 * Reverses the next N messages that are received. E.g. for N=4, {1,2,3,4,5} will be sent up as {4,3,2,1,5}. Blocks
 * until N messages have been received. Used for testing
 * @author Bela Ban
 * @since  4.1.5
 */
@MBean(description="Queues the next N messages that are received and passes them up in reverse order")
public class REVERSE extends Protocol {

    @ManagedAttribute(description="Number of messages to reverse.",writable=true)
    protected volatile int         num_msgs_to_reverse;
    protected Predicate   filter; // if set and false -> mesage will be sent up the stack

    protected final Deque queue=new ConcurrentLinkedDeque<>();

    public int     numMessagesToReverse()       {return num_msgs_to_reverse;}
    public REVERSE numMessagesToReverse(int n)  {num_msgs_to_reverse=n; return this;}
    public Predicate filter()          {return filter;}
    public REVERSE filter(Predicate f) {this.filter=f; return this;}
    @ManagedAttribute(description="Number of queued messages")
    public int     queuedMessages()             {return queue.size();}

    public void stop() {
        flush();
        super.stop();
    }

    public Object up(Message msg) {
        if(num_msgs_to_reverse == 0 || (filter != null && !filter.test(msg)))
            return up_prot.up(msg);
        if(queue.add(msg) && queue.size() >= num_msgs_to_reverse)
            flush();
        return null;
    }

    public void up(MessageBatch batch) {
        for(Iterator it=batch.iterator(); it.hasNext();) {
            Message msg=it.next();
            if(num_msgs_to_reverse == 0 || filter != null && !filter.test(msg))
                continue;
            if(queue.add(msg) && queue.size() >= num_msgs_to_reverse)
                flush();
            it.remove();
        }
        if(!batch.isEmpty())
            up_prot.up(batch);
    }

    @ManagedOperation(description="Sends all queued messages and disables queueing for subsequent messages")
    public REVERSE flush() {
        Message msg;
        while((msg=queue.pollLast()) != null) {
            up_prot.up(msg);
        }
        num_msgs_to_reverse=0;
        return this;
    }
}