[rabbitmq-discuss] Clustering - communication

Tue Jan 31 11:30:48 GMT 2012

Hi Dan,

> Can anyone give me some pointers? 

You seem to have done everything right.

> Do both servers need to be
> stop_app'd at the same time for this to succeed or is it something
> else?

Well, one of them has to be.  If you run 'stop_app' on a RabbitMQ
broker, it stops.  It stays loaded into memory, but otherwise it's
completely stopped, so it closes open connections and doesn't open new
ones.

When you cluster, the database on the clustering node needs to be
stopped, so it has to be stop_app'd.  The database on the target node
generally has to be started, so that node has to be started.

The *target* nodes also have to be started for rabbitmqctl to work.

> Also, will stop_app kill any messages? I'm looking not to.

Stop_app is the equivalent of a clean shutdown, so, it will kill
transient messages/queues, but save to disc persistent messages/durable
queues/any other configuration.  Again, when it's stopped, it won't have
any connections, so it won't get new messages.

> have the
> same .erlang.cookie file (had to hexedit to get it exact).

That sounds a bit worrying.  Could you just put some human readable text
in both (e.g. "test"), make sure that both nodes are started, and try
the rabbitmqctl status command from one to the other?

Cheers,
Alex

On Tue, Jan 31, 2012 at 10:07:26AM +0000, Dan Dart wrote:
> Hi all,
> 
> I'm having trouble getting two nodes talking. For reference they're
> called backend and back2 - and each is in each other's hosts file
> (with and without a FQDN).
> 
> Each can connect to each other on ports 4369 and 5672 - and have the
> same .erlang.cookie file (had to hexedit to get it exact).
> They're not connecting through the same network but they're not far
> away (<1ms ping)
> When I try to cluster (taking the node down using stop_app first) - I
> get the error:
> 
> Error: {no_running_cluster_nodes,[rabbit at backend],[rabbit at backend]}
> 
> When I try to use rabbitmqctl -n rabbit at back2 status, from backend, I get:
> 
> Status of node rabbit at back2 ...
> Error: unable to connect to node rabbit at back2: nodedown
> diagnostics:
> - nodes and their ports on back2: [{rabbit,48765}]
> - current node: rabbitmqctl18870 at localhost
> - current node home dir: /var/lib/rabbitmq
> - current node cookie hash: (the same each time)
> 
> and vice versa.
> 
> Can anyone give me some pointers? Do both servers need to be
> stop_app'd at the same time for this to succeed or is it something
> else?
> Also, will stop_app kill any messages? I'm looking not to.
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