[jboss-jira] [JBoss JIRA] (JGRP-1644) NAKACK2 violates FIFO property

[Bela Ban (JIRA)]

    [ https://issues.jboss.org/browse/JGRP-1644?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12781686#comment-12781686 ] 

Bela Ban commented on JGRP-1644:
--------------------------------

Hard to believe, I routinely run MPerf before releasing with millions of messages, and they're never delivered out of order. MPerf also tags each message with an application seqno.
Do you have a perf test that reproduces the issue ?

Are you sure you're not sending with multiple threads, or tag your messages as OOB ?

*If* NAKACK2 delivered messages in an incorrect order, that would be a big bug and I'm interested in getting to the bottom of it.
                
> NAKACK2 violates FIFO property
> ------------------------------
>
>                 Key: JGRP-1644
>                 URL: https://issues.jboss.org/browse/JGRP-1644
>             Project: JGroups
>          Issue Type: Bug
>    Affects Versions: 3.3.1
>         Environment: Ubuntu 12.04 LTS, kernel 3.2.0-24-generic #39-Ubuntu SMP Mon May 21 16:52:17 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux, Java 1.7.0_21
>            Reporter: Vadim Tsesko
>            Assignee: Bela Ban
>             Fix For: 3.4
>
>
> In the [documentation documentation|http://www.jgroups.org/manual/html/protlist.html#ReliableMessageTransmission] it is stated that:
> {quote}
> NAKACK provides reliable delivery and FIFO (= First In First Out) properties for messages sent to all nodes in a cluster.
> {quote}
> and
> {quote}
> NAKACK2 was introduced in 3.1 and is a successor to NAKACK (at some point it will replace NAKACK). It has the same properties as NAKACK, but its implementation is faster and uses less memory, plus it creates fewer tasks in the timer.
> {quote}
> I have observed that sometimes multicast messages are received out of order.
> We use the following protocol stack configuration:
> {code:xml}
> <config xmlns="urn:org:jgroups"
>         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
>         xsi:schemaLocation="urn:org:jgroups http://www.jgroups.org/schema/JGroups-3.3.xsd">
>     <UDP bind_addr="match-interface:$interface"
>          bind_interface="$interface"
>          bind_port="$unicastPort"
>          ip_ttl="128"
>          mcast_addr="$multicastGroup"
>          mcast_port="$multicastPort"
>          singleton_name="udp-transport"/>
>     <PING return_entire_cache="true"
>           break_on_coord_rsp="false"/>
>     <MERGE3/>
>     <FD_SOCK/>
>     <FD_ALL/>
>     <VERIFY_SUSPECT/>
>     <BARRIER/>
>     <pbcast.NAKACK print_stability_history_on_failed_xmit="true"/>
>     <pbcast.STABLE/>
>     <pbcast.GMS/>
>     <MFC max_credits="8M"/>
>     <FRAG2/>
>     <RSVP/>
> </config>
> {code}
> As you can see, mostly we use the defaults.
> The messages are being sent from a single thread using the following code:
> {code:java}
> channel.send(new Message(null, msg))
> {code}
> Each message has size from 300 KB up to 4 MB. The message rate is 1-5 messages per second.
> We have a sequential counter inside each message being sent. Sometimes the messages are received out of order, for instance:
> {code}
> #1198
> #1199
> #1200
> #1202
> #1201
> #1203
> #1204
> {code}
> If we replace {{NAKACK2}} by {{NAKACK}} the problem disappears -- everything works as expected (FIFO).
> If we replace JGroups-based transport by ZeroMQ-based transport (actually running over EPGM and being used for a year) everything works as expected (FIFO) -- just to let you know, that there are no bugs in out message numbering logic.

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