[rabbitmq-discuss] A cluster on a single machine

Mon May 7 12:05:10 BST 2012

Hi Simon,

Yup, I spotted that just after posting. It now reads:

...
rabbitmqctl -n rabbit3 stop_app
rabbitmqctl -n rabbit3 reset
rabbitmqctl -n rabbit3 cluster rabbit1 at dfooks-ubuntu64rabbit2@dfooks-ubuntu64
rabbitmqctl -n rabbit3 start_app

However, after that fix I'm still seeing the same error.

Thanks for the tip on RABBITMQ_PID_FILE (it should be documented that it
doesn't work with -detached).

On 4 May 2012 18:00, Simon MacMullen <simon at rabbitmq.com> wrote:

> On 04/05/12 17:46, David Fooks wrote:
>
>> Hi,
>>
>> I'm trying to emulate the guide here:
>> http://www.rabbitmq.com/**clustering.html<http://www.rabbitmq.com/clustering.html>
>>
>> But I'm having a lot of issues! Every time I run I seem to be getting a
>> different crash. Is this feature actually supported in 2.8.1?
>>
>
> Yes! But running a cluster on a single machine is more fiddly than running
> it on separate machines as you need to make sure the nodes don't tread on
> each other. I don't think that's your problem though.
>
>  Is there a proper way to completely reset all of the state that rabbitmq
>> creates about other nodes/the cluster? My clean up script at the moment
>> looks like this:
>>
>> rm /var/run/rabbitmq/*
>> rm -f /var/log/rabbitmq/*
>> rm -rf /var/lib/rabbitmq/*
>>
>
> OK, that should be fine.
>
>  Here is my start-up script (I'm running this with sudo):
>>
>> RABBITMQ_NODE_PORT=5672 RABBITMQ_NODENAME=rabbit1
>> RABBITMQ_SERVER_START_ARGS="-**rabbitmq_mochiweb listeners
>> [{mgmt,[{port,55672}]}]" rabbitmq-server -detached
>> RABBITMQ_NODE_PORT=5673 RABBITMQ_NODENAME=rabbit2
>> RABBITMQ_SERVER_START_ARGS="-**rabbitmq_mochiweb listeners
>> [{mgmt,[{port,55673}]}]" rabbitmq-server -detached
>> RABBITMQ_NODE_PORT=5674 RABBITMQ_NODENAME=rabbit3
>> RABBITMQ_SERVER_START_ARGS="-**rabbitmq_mochiweb listeners
>> [{mgmt,[{port,55674}]}]" rabbitmq-server -detached
>>
>> ps -ef | grep rabbit1 | grep -v grep | awk '{print $2}' >
>> /var/run/rabbitmq/rabbit1.pid
>> ps -ef | grep rabbit2 | grep -v grep | awk '{print $2}' >
>> /var/run/rabbitmq/rabbit2.pid
>> ps -ef | grep rabbit3 | grep -v grep | awk '{print $2}' >
>> /var/run/rabbitmq/rabbit3.pid
>>
>
> Ew, those ps'es are not nice. You may prefer to set RABBITMQ_PID_FILE for
> each startup, although this means you cannot use -detached (instead just
> background it with &)
>
>  rabbitmqctl -n rabbit1 wait /var/run/rabbitmq/rabbit1.pid
>> rabbitmqctl -n rabbit2 wait /var/run/rabbitmq/rabbit2.pid
>> rabbitmqctl -n rabbit3 wait /var/run/rabbitmq/rabbit3.pid
>>
>> rabbitmqctl -n rabbit1 stop_app
>> rabbitmqctl -n rabbit1 reset
>> rabbitmqctl -n rabbit1 start_app
>>
>> rabbitmqctl -n rabbit2 stop_app
>> rabbitmqctl -n rabbit2 reset
>> rabbitmqctl -n rabbit2 start_app
>>
>> rabbitmqctl -n rabbit3 stop_app
>> rabbitmqctl -n rabbit3 reset
>> rabbitmqctl -n rabbit3 start_app
>>
>
>  rabbitmqctl -n rabbit1 status
>> rabbitmqctl -n rabbit2 status
>> rabbitmqctl -n rabbit3 status
>>
>> rabbitmqctl -n rabbit3 stop_app
>> rabbitmqctl -n rabbit3 cluster rabbit1 at dfooks-ubuntu64
>> rabbit2 at dfooks-ubuntu64
>> rabbitmqctl -n rabbit3 start_app
>>
>
> But here's the problem. You need to do:
>
> rabbitmqctl -n rabbit3 stop_app
> rabbitmqctl -n rabbit3 reset
> rabbitmqctl -n rabbit3 cluster rabbit1 at dfooks-ubuntu64 \
>    rabbit2 at dfooks-ubuntu64
> rabbitmqctl -n rabbit3 start_app
>
> Instead you are doing something like (considering only rabbit3):
>
> rabbitmqctl -n rabbit3 stop_app
> rabbitmqctl -n rabbit3 reset
> rabbitmqctl -n rabbit3 start_app
> rabbitmqctl -n rabbit3 stop_app
> rabbitmqctl -n rabbit3 cluster rabbit1 at dfooks-ubuntu64 \
>    rabbit2 at dfooks-ubuntu64
> rabbitmqctl -n rabbit3 start_app
>
> Clustering can only take place when the state is *completely* reset - the
> fact that you are starting and stopping the app again between reset and
> cluster is recreating a blank database...
>
> <snip>
>
>> {merge_schema_failed, "Incompatible schema cookies.
>>
> <snip>
>
> ...which is exactly what would lead to this error message.
>
> And yes, at some point we hope to make clustering easier to use.
>
> Cheers, Simon
>
> --
> Simon MacMullen
> RabbitMQ, VMware
>
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