[rabbitmq-discuss] RabbitMQ 'hang' when trying to access HA queues

Thu Sep 12 15:18:06 BST 2013

Hi Matthias,

Suchak and I got together and came up with a set of questions regarding our issue which if you were able to give feedback on, would be most useful.

We cannot be sure that during our 'hang' that publishers were blocked but from application behaviour, it seems likely, or at least they did not receive confirms. We do know that calls to queue declare (via the Java client) and rabbitmqctl list_queues both failed to return.

Our questions are:

- Are there any known conditions that you are aware of that would cause list_queues or declare queue to hang? If you are only able to indicate possible areas of the system that cause issue that would be helpful, e.g. if the MNESIA tables holding the queue metadata failed in some way (due to an infrastructure issue at the networking or disk level), could that explain one queue 'hanging'?
- The current documentation for RabbitMQ 3.x describes many situations where flow control kicks and publishers are blocked. We understand that flow control at 2.7.1 is rudimentary but it would simply involve publishers blocking (on basic publish) but could it in any way explain what we saw? (We are guessing not but wanted somebody who knows to confirm!).
- Some of our RabbitMQ clients are written in erlang and are embedded (with a significant amount of other application code) within the same cluster as RabbitMQ. Are there issues with this approach at 2.7.1?
- We are running the broker (and collocated application code) on Erlang R15B (erts-5.9) on Solaris SPARC. Again, are there any known issues with this configuration?

Thanks again for any support you can give us on this issue, I am aware you are going above and beyond the usual level of support especially given the version of RabbitMQ in use.

Regards, Andrew.

-----Original Message-----
From: Matthias Radestock [mailto:matthias at rabbitmq.com] 
Sent: 12 September 2013 11:55
To: Andrew Rendell
Cc: Discussions about RabbitMQ; Nick Gill (ngill at gopivotal.com); Suchak Jani
Subject: Re: [rabbitmq-discuss] RabbitMQ 'hang' when trying to access HA queues

Andrew,

On 12/09/13 11:41, Andrew Rendell wrote:
>> Was there anything unusual in the logs?
>
> No. This was what was most disconcerting about this issue.

Hmm. Quite.

> Would it be correct to say that since 2.7.1 there has been major 
> rewrites of the HA queue implementation

It's not been rewritten as such, but has undergone substantial change and improvement. There have been nearly 40 bug fixes to mirrored queues since 2.7.1.

> it is probable there were very few people using 2.7.1 in HA mode

...for a considerable length of time and/or with extensive testing...

> so a defect might have remain undiscovered?

Correct.

Matthias.

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