[erlang-questions] Dependencies, included applications and supervision

[Jay Nelson]

Not every application can be separate. We have an application called ‘presence_server’
which is embedded in every node. When the server comes up, and is finished with its
full initialization, it announces “service available” so that other nodes can contact it. If
the presence_server is run as a sibling application, it can go down and cause services
to be unavailable until it is restarted.

The desire to have all applications independent is laudable, but code reuse allows us
to have ‘presence’ capabilities embedded in more than one application and be reliable
because it is restarted by the supervisor hierarchy. Your teammates fears of inconsistent
dependencies are real and well-founded even if you haven’t encountered a failure
situation yet.

jay