Re: [javagroups-users] view synchrony guarantees?

[Bela B. <be...@ya...>]

I modified and added your demo to JGroups: 
tests/other/org//jgroups/tests/ViewDeliveryDemo.

I get the violation too. Vladimir and I will investigate

Robert Newson wrote:
> Hi,
>
> I'm running a test where I have eight machines each sending batches of 
> messages, leaving and joining a channel at random.  The messages 
> contain the current ViewId. On receipt that ViewId is compared to the 
> local ViewId. My stack is the "udp" one in stacks.xml, though not over 
> a multiplexed channel.
>
> Given the presence of the FLUSH protocol and its description in its 
> Javadoc, I was not expecting to see a message arrive in a later view 
> than which it was sent in. As it happens, it does. It's a low rate, my 
> batches are up to 5000 messages and I sent 1 or 2 such messages every 
> few seconds, but I expected none.
>
> FLUSH states this;
>
> "Before installing a new view V2, flushing would ensure that all 
> messages *sent* in the current view V1 are indeed *delivered* in V1, 
> rather than in V2 (in all non-faulty members). This is essentially 
> Virtual Synchrony."
>
> This appears not to be the case with 2.6.1 at least.
>
> here's a sample violation which shows message sent in view 21 arriving 
> in view 22 (the coordinator of the views is the same).
>
> VIOLATION: message sent in view [192.168.164.227:33198|21] received in 
> [192.168.164.227:33198|22]
>
> The full source code for the demo is below;
>
>
> import java.security.SecureRandom;
> import java.util.Random ;
>
> import org.jgroups.Address;
> import org.jgroups.Channel;
> import org.jgroups.Message;
> import org.jgroups.Receiver;
> import org.jgroups.View;
> import org.jgroups.ViewId;
>
> /**
>  * Verify that all messages are delivered in the view they are sent in
>  * regardless of members joining, leaving or crashing.
>  *
>  * @author rnewson
>  *
>  */
> public final class ViewDeliveryDemo {
>
>     private static class MyReceiver implements Receiver {
>
>         @Override
>         public byte[] getState() {
>             // Ignored.
>             return null;
>         }
>
>         @Override
>         public void receive(final Message msg) {
>             final Object obj = msg.getObject ();
>             if (obj instanceof ViewId) {
>                 final ViewId sent_in_vid = (ViewId) obj;
>                 final ViewId arrived_in_vid = channel.getView().getVid();
>                 if (!sent_in_vid.equals(arrived_in_vid)) {
>                     System.out
>                             .printf(
>                                     "VIOLATION: message sent in view 
> %s received in %s\n",
>                                     sent_in_vid, arrived_in_vid);
>                 }
>             } else {
>                 System.out.println("ERROR: unexpected payload: " + obj);
>             }
>         }
>
>         @Override
>         public void setState(byte[] state) {
>             // Ignored.
>         }
>
>         @Override
>         public void block() {
>
>         }
>
>         @Override
>         public void suspect(Address suspected_mbr) {
>
>         }
>
>         @Override
>         public void viewAccepted(View new_view) {
>
>         }
>
>     }
>
>     private static final int SEND = 0;
>     private static final int REOPEN = 1;
>     private static final int RECONNECT = 2;
>
>     private static Channel channel;
>     private static final Random random = new SecureRandom();
>
>     public static void main(final String[] args) throws Exception {
>         connect();
>         while (true) {
>             switch (random.nextInt(3)) {
>             case SEND:
>                 send();
>                 break;
>             case REOPEN:
>                 reopen();
>                 break;
>             case RECONNECT:
>                 reconnect();
>                 break;
>             default:
>                 assert false;
>             }
>             Thread.sleep(random.nextInt(2000));
>         }
>     }
>
>     private static void send() throws Exception {
>         System.out.println("Sending batch of messages.");
>         for (int i = 0, max = random.nextInt(1000); i < max; i++) {
>             channel.send(null, null, channel.getView().getVid());
>         }
>     }
>
>     private static void reopen() throws Exception {
>         System.out.println("closing and reopening.");
>         channel.close();
>         Thread.sleep(random.nextInt(5000));
>         channel.open();
>         connect();
>     }
>
>     private static void reconnect() throws Exception {
>         System.out.println("disconnecting and reconnecting.");
>         channel.disconnect();
>         Thread.sleep(random.nextInt(5000));
>         connect();
>     }
>
>     private static void connect() throws Exception {
>         if (channel == null) {
>             channel = DemoUtils.getChannel(null);
>         }
>         channel.setReceiver(new MyReceiver());
>         channel.connect("view_test");
>     }
> }
>
> note: DemoUtils.getChannel(null) calls createChannel() on a 
> JChannelFactory for which setMultiplexerConfig(" stacks.xml") has been 
> called. Also, AUTO_RECONNECT has been set to true.
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-- 
Bela Ban
Lead JGroups / Clustering Team
JBoss - a division of Red Hat