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From "Rob Waite (JIRA)" <>
Subject [jira] [Commented] (AMQNET-409) Failover fails under load. Client goes into reconnect loop.
Date Wed, 06 Feb 2013 06:55:12 GMT


Rob Waite commented on AMQNET-409:

We actually ran into another after fixing the above one. We are currently going to catch exceptions
in the *Format() calls in Tracer.cs and make a best attempt to print what the caller was trying
to pass in.

I would think the proper fix is to change all the caller code for *Format() but the Tracer
change is easier ;)
> 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
> We were testing failover under heavy 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 prod 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:
> "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)"
> 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 many places in the code. I would think that either the Tracer should
handle this exception or trim illegal characters or DebugFormat should not use concatenation
for the first param.

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