[rabbitmq-discuss] Debugging problems with federation plug in.

[Simon MacMullen]

On 24/06/2014 22:44, Dan Galewsky wrote:
> We have a federation with 4 nodes.
>
> We are continually fighting problems with messages making it to some
> nodes in the exchange and not to others.
>
> Current situation is that I can drop a message into the federated
> exchange and all three downstream nodes see my message.
>
> Messages can be sent to me from two of the nodes but not the third.
>
> They put a message into the federated exchange and the other two nodes
> see the message and my node does not.

What does the link status at your end say? You should have a link for 
every (federated exchange, upstream) pair. Federation works on a pull 
model so your node is responsible for getting messages from the upstream.

http://www.rabbitmq.com/federation-reference.html#status

> Something I have noticed is that on the Queues tab - in the Parameters
> column of the Rabbit webapp - I see "D ARGS" for the nodes that can talk
> to me and only "D" on the node that is unable to talk to me.

The difference is one of version, recent versions of the federation 
plugin set x-internal-purpose: federation so you can identify 
federation-internal things. It should just mean that node is running an 
older RabbitMQ, it should still work.

> And if I hover over the ARGS string in the UI - I get a hover label that
> says "x-internal-purpose: federation" which makes me think that somehow
> the other node and I are not federated (even though I can send them
> messages through the federated exchange).

Note that each federation link is unidirectional, for bidirectional 
federation you have two links. So it can be working one way and broken 
the other.

Cheers, Simon