[erlang-questions] establishing preconditions at startup

[Garry Hodgson]

I'm working on an application whose startup phase relies on some 
potentially lengthy setup of tunnels and such before we can start up our 
ranch listeners and start regular communications. I've thought of a 
number of approaches (application dependencies, supervisors, deferred 
initialization using handle_info, etc) that could ensure this 
sequencing, but they feel awkward, like I'm working against the grain.

So how do other people handle this? Is there canonical erlangy way to do 
it? I reflexively avoid doing long running things in otp callbacks, but 
I expect there are better and worse places/times to do this.

Thanks