this is where the special “exit from parent” is implemented: otp/gen_server.erl at master · erlang/otp · GitHub

This is excellent. Thankyou so much for writing this!

Just one point: I think there is a further difference in behaviour if the process doing the killing is the direct parent of the child? I’m actually not sure I understand the specifics, but there was a post on elixirforum a month or so back about this and the insight was that the child can’t catch it’s own exit if the thing sending the message is the direct parent? I think if this is correct then it would be quite nice to get this documented in your rather comprehensive write-up on this stuff!

I confess I still have a lot of doubts over how to correctly use OTP and especially how best to link some children and guarantee cleanup. I quite like the “parent” library for some of these things (“director” seems nice as well). I think it’s clear from your document that there are a few preferred ways to kill processes if you want to allow them to call their terminate() function. It does leave me with some doubts on how to handle this as a library author as well…

Looking forward to see if you do a followup on this on? Perhaps with regards to how to build robust links, cleanup on failure, monitor callers to ensure we terminate when our invoker terminates, etc?

I think so too. Links are bidirectional, see Process — Elixir v1.12.3

But you can implement some stuff that makes one process behave like a parent.
See Parent - custom parenting of processes

Thank you for this great and deadly blog-series!

I got round to writing up the parent / child exit signal behaviour. Death, Children, and OTP | The log of Paul Wilson

I’ll link up the blog posts tomorrow. Thanks for pointing out the behaviour change.

Oh, nice. Thanks. So the OTP contract specifies special behaviour for when the parent dies and, of course, GenServers follow that contract. As I was specifically saying this was about OTP processes, then it is relevant. I’ll mention that somewhere.