Which part or just in general ops with Erlang?

Overall I would say this book is a good start https://www.erlang-in-anger.com/

Supervisors are just a general pattern in Erlang. Any book will have something about it. I like this one: https://learnyousomeerlang.com/supervisors

Restarting frequency and limits are just one of the parameters you specify. So don't need to do anything fancy or special there.

Hot code loading might not be as obvious: http://erlang.org/doc/reference_manual/code_loading.html but is essentially just compiling the module on the same VM version (or close by, no more than 2 version away), copying it to the server in the same path as the original. The original could be save to a backup file. The do `l(modulename)` to load it.

For tracing I recommend http://ferd.github.io/recon/. Erlang in Anger book will also have example of tracing. http://erlang.org/doc/man/dbg.html has some nice shortcuts too, but be careful using it in production is it doesn't have any overload protection. So if you accidentally trace all the messages on all the processes, you might crash your service :-)

Tracing is mainly what I was going for. I'm very familiar with the various patterns and the run time, but I haven't seen the tracing aspects referenced in as much detail.

Thanks!