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From "Rob Waite (JIRA)" <>
Subject [jira] [Comment Edited] (AMQNET-409) Failover fails under load. Client goes into reconnect loop.
Date Wed, 06 Feb 2013 09:57:12 GMT


Rob Waite edited comment on AMQNET-409 at 2/6/13 9:55 AM:

Attached Trace.cs resolved our issues. Failover seems very solid so far when exception is
not allowed out. Sometimes we still have a disconnection related to the unmatched ack... but
it reconnects once and appears to function properly. Still need to perform test proving all
messages are actually delivered but seems good so far. Our system is tolerant of duplicate
messages... just need to confirm that all messages are delivered and not incorrectly acked.
      was (Author: absynthe49):
    Attached Trace.cs resolved our issues. Failover seems very solid so far when exception
is not allowed out.
> Failover fails under load. Client goes into reconnect loop.
> -----------------------------------------------------------
>                 Key: AMQNET-409
>                 URL:
>             Project: ActiveMQ .Net
>          Issue Type: Bug
>          Components: ActiveMQ
>    Affects Versions: 1.5.6
>         Environment: Should not matter. AMQ is on Linux, Client is on Windows with .NET
>            Reporter: Rob Waite
>            Assignee: Jim Gomes
>         Attachments: Tracer.cs
> We were testing failover under load. We have a queue that I placed 500k messages in.
I then have 5 consumers pulling them as fast as they can. The operations are noops essentially...
so messages are consumed in our case at around 500 messages per second with our test servers.
> I would bring up the consumers and they would be consuming away. I would then "kill -9"
AMQ and then observe the client. From the AMQ web admin... they would come back but you would
see the 5 consumers go back and forth between 5 and 0 and comsumption went down from 500/s
to about 3/s.
> Looking at AMQ logs... there was a series of errors like this " Async error occurred:
javax.jms.JMSException: Unmatched acknowledge: MessageAck" and then there would be a couple
variations of exceptions regarding the connection being lost (EOFException, broken pipe, etc).
There would be an endless loop creating this pattern.. a message about an unmatched ack...
a message about a socket dying... then reconnection from the client... on and on.
> I can provide the full stack traces but I have already found the line that seems to cause
the client to reconnect, fail, disconnect ad infinitum.
> In our particular case... there is a line in the NMS.ActiveMQ source in Connection.cs
line 950 (in Apache.NMS.ActiveMQ-1.5.6-src) that looks like:
> {code:title=Connection.cs|borderStyle=solid}
> Tracer.DebugFormat("Connection[{0}]: Async exception with no exception listener: " +
error, this.ConnectionId);
> {code}
> The "error" variable was populated with:
> {noformat} 
> "Apache.NMS.NMSConnectionException: Unmatched acknowledge: MessageAck {commandId = 1146,
responseRequired = false, ackType = 2, consumerId = ID:kcccccc-54512-634956893773509011-1:10:3:1,
firstMessageId = ID:qaaaaa-54879-634956774946428300-1:0:1:2:60645, lastMessageId = ID:qaaaaaa-ops01-54879-634956774946428300-1:0:1:2:60645,
destination = queue://AAA.RwwTest.Failover, transactionId = null, messageCount = 1, poisonCause
= null}; Could not find Message-ID ID:qaaaaaa-ops01-54879-634956774946428300-1:0:1:2:60645
in dispatched-list (start of ack)"
> {noformat} 
> Notice that there are curly braces in there... when you try to concat this with the first
parameter in the Tracer.DebugFormat call you get a System.FormatException with the message
"Input string was not in a correct format."
> Changing the line to the following seemed to fix the particular case we were seeing..
but I imagine other use cases may cause the same:
> {code:title=Connection.cs|borderStyle=solid}
> Tracer.DebugFormat("Connection[{0}]: Async exception with no exception listener: {1}",
this.ConnectionId, error);
> {code}
> It seems odd that String.Format style logging is used but a string is still concatenated.
This seems to happen in a few places in the code. I would think that either the Tracer should
handle this exception, trim illegal characters or DebugFormat should not use concatenation
for the first param.
> I have not dug incredibly deeply into the source... but I imagine when an exception was
thrown by the log call... it bubbled up and pissed something off. The connection seems to
have been closed by the client... but it did not remove state from the previous attempt. When
it reconnected, the same occurred and then there was the looping effect.

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