RabbitMQ 3.6.2 RC1 -- Disablement of rates_mode creates a large queue that is not handled

[John F]

In order to have a stable environment we've made a lot of tests and adjustments. One of these was done 2-3 hours ago where we disable the rates_mode on the rabbitmq_management plugin by setting rates_mode to none.

Now when we log into the management portal we see a message:

The management statistics database currently has a queue of 175772 events to process. If this number keeps increasing, so will the memory used by the management plugin.

So now our questions are:

• will this just increase and increase and what would then happen?
• is this working as it should?
• do we need to do other adjustments to solve this?

We can crash RabbitMQ during load tests because statistics uses a huge amount of memory and then crashes our nodes in the cluster. We've disabled this in order to see if we can crash RabbitMQ with this disabled. We were not expecting events to queue up like this.

[Michael Klishin]

And re-enabling it makes the issue go away? How can we reproduce? Please understand that it is really really hard to improve or even reason about something we do not know how to reproduce.

We haven't seen this message with 3.6.2. Disabling rates should have the opposite effect.

As for what that message means and what happens next, see management issue 41. We have explained this

many times in the past.

3.6.2 has fixes that are crucially important for some users. We cannot delay it for much longer so please please provide a way to reproduce this issue.

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[John F]

And re-enabling it makes the issue go away? How can we reproduce? Please understand that it is really really hard to improve or even reason about something we do not know how to reproduce.

Yes the message is only shown when rates_mode is set to none. This is an extract from our config:

{  rabbitmq_management        ,[
                              { listener                    ,[{ port                     ,    15672                                              }]},
                              { rates_mode                  ,   none                                                                             }
                              ]},

My guess is that it can be reproduced in other environments by simple setting rates_mode to none for the rabbitmq_management plugin.

We haven't seen this message with 3.6.2. Disabling rates should have the opposite effect.

That was also our understanding.
 

As for what that message means and what happens next, see management issue 41. We have explained this

many times in the past.

Okay. Will do.

3.6.2 has fixes that are crucially important for some users. We cannot delay it for much longer so please please provide a way to reproduce this issue.

 
Us including ;-) Don't you get this message if you set rates_mode to none for all nodes in a RabbitMQ cluster?

[John F]

3.6.2 has fixes that are crucially important for some users. We cannot delay it for much longer so please please provide a way to reproduce this issue.

Please release 3.6.2 with the LDAP fix ASAP because that is currently the most crucial problem we are facing.

If you can make a release with that fix then we can - hopefully - eliminate one problem from our list.

When do you expect to release it? Today? Now? ;-)

[Michael Klishin]

We will release an RC2 later today with the LDAP fix you're looking for, then

see if we can improve the new collector a bit more and maybe reproduce the STOMP issue.

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MK

Staff Software Engineer, Pivotal/RabbitMQ

[John F]

I can confirm that the 3.6.2 RC2 fixed the issue we saw with many messages being queued for the statistics module :-)