I have a web service written in Cowboy and I am planning to use RabbitMQ as the DB layer. So my Cowboy service will be one of the producer which writes to the queue and the consumer writes to the database. There are couple more asynchronous tasks that will come from another service (not Cowboy).
Now the question is where these consumers should go. Should these be part of single erlang app or should I create separate Erlang app for all the consumers. Any advice would be highly appreciated.
Since Erlang is not the exclusive producer, and since one can usually imagine consumers running without knowledge of the producers, having separate applications is not a bad idea at all. You can have multiple top-level applications in a single Erlang release (that's what the dependencies are, really), so you can always put all the code in the same repository (I usually have a top level apps/ directory for these), and if needed later on split them out to separate repos.
Having them as separate applications certainly makes deciding later on to distribute the application across multiple erlang nodes easier: just start the relevant producer applications s on some nodes, and the consumer application on others.
So while either way will probably work, separate apps is probably a cleaner design and keeps the door open for future expansion in a slightly nicer way.
