[rabbitmq-discuss] Federation vs Shovel

[Danny Beutler]

Hello,
I am trying to decide between using Shovel or Federation. Our use case is
as follows:
We have two datacenters: east coast and west coast in the US. We have two
clustered rabbitmq nodes in each site. We have messages which are published
at each site which need to be reliably consumed at both sites. For example,
a message published to exchange A at Site A will need to be consumed at
both site A and site B. The messages, exchanges, and queues involved need
to be durable, mirrored, etc. in order to ensure reliable delivery of each
and every message.

Initially, I had leaned toward the shovel plugin for a couple of reasons.
1) The documentation for shovel seems for straightforward. Using Shovel, I
know what happens to the messages in transit because they follow the same
message flow as "normal" messages. The plan is to have a fanout exchange at
each site which publishes to both a queue for local consumption and a queue
that is then shoveled across the WAN to an exchange than points to just the
queue for local consumption and vice versa.
Using Federation, I am not fully aware of what would happen. Say I have a
fanout exchange configured at Site A. A queue at Site A connects to this
queue for local consumption of the messages. Site B then attaches to the
exchange via federation. My understanding is that there is then an upstream
queue created. If Site B then goes offline, what happens to the messages
published to the fanout exchange in Site A. Will the messages sit in the
upstream queue until both the queue and the remote are available to fanout
messages to?

2) Shovel has "More Control" according to the documentation.

My questions are: Am I missing the boat? Would Federation be much more
simple to setup? Would Federation even work in this scenario?

In addition: I would like to configure this whole thing via Puppet. I know
how to do it in the rabbitmq config for shovel but wouldn't this require a
restart when configuration changes are made? Also, would the federation
configuration methods via the API lend itself to more simple Puppetization
through simple API calls for Federation setup?

Thanks,
Danny
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