[rabbitmq-discuss] Managing channels, esp wrt short lived publishers/consumers

Fri Mar 18 18:52:29 GMT 2011

Hey list,

I'm trying to figure out the best way to manage channel creation in my 
app. Currently, any process that needs to publish or consume gets a 
channel and I realize it is probably horribly inefficient, but as a 
prototype I wasn't too concerned. Now that we're moving forward, I want 
to get this cleaned up before I get too much further along.

I have a setup something like:

[App, App, App] <---> [AMQP] <--> Engine <--> Client

So a client makes a request to the Engine, which creates two processes, 
one to publish events from the client, and one to consume commands from 
the Apps and relay them to the client.

[App, App, App] <--> [AMQP] <-- ReqEvts <-- Client
[App, App, App] <--> [AMQP] --> ReqCtl --> Client

Ideally we'll be handling several hundreds of requests per second from 
clients. So the ReqEvts process pumps 10 or so messages in rapid 
succession at the beginning of a request, heartbeats every 20 or so 
seconds, then pumps another 10 or so messages at the end of the request. 
Requests may last 1 second (so setup and tear down bursts happen almost 
on top of each other) or may last minutes or hours. Meanwhile, the 
ReqCtl receives commands from a targeted exchange from the Apps to relay 
to the Client.

Each App has a queue that it binds to a targeted exchange and one or 
more topic exchanges. In general it receives most messages off the topic 
exchanges and publishes to the targeted exchange.

So, hopefully that gives a broad overview. The Apps and the Engine 
pieces are all on different servers.

So right now each server has an instance of rabbitmq running, and is 
clustered to all the other servers (Apps and Engine, currently four 
total servers but expandable). What I'm not sure about is how to manage 
each server's connection and channels. Each server has a gen_server 
managing the connection to rabbit, as well as the channels. So when a 
pid requests to publish or consume or declare a queue, the gen_server 
checks if the pid is known and uses that channel, or creates a new 
channel and stores the association. With all of these potentially 
short-lived consumers and publishers, I see a LOT of channel 
creation/destruction going on and wonder if there's a better way? Should 
I not have hidden channels behind a gen_server?

My initial thought is to have a dedicated channel for all publishers on 
the server to send over, a dedicated channel for any queue declarations, 
and a channel for each process that is consuming from a queue. Am I 
serializing too much with this setup? Other ideas for how to manage 
channels?

Any guidance is appreciated!

Thanks,
James