Thanks for all the information here! I ended up deciding not to use Process.exit. Instead I followed @ityonemo 's suggestion of sending a “soft halt” by doing a GenServer.call(pid, :halt_and_cleanup) , this gives me the handle_call for this explicit type of termination, which in turn lets me publish the “child died” message on my broker and then safely return {:stop, :normal, :ok, state}.

I also adopted the use of the Registry and I’m now storing the child pids there along with their keys.

If the process is actively handling messages (versus being blocked in a call or similar), consider adding an explicit “hey could you please shut down” message to the GenServer’s public API. The handle_call head for that can return {:stop, :shutdown, :ok, state} and the GenServer will exit with reason :shutdown.

Otherwise, signaling from outside is done via Process.exit/2 and functions built using it. It’s useful to understand exactly what “signaling a process to exit means”:

• If any Erlang process gets an exit signal with a reason of :kill, it will exit immediately with the reason :kill.

• If a process that isn’t trapping exits gets an exit signal, it will exit immediately with the same reason.

• If a GenServer is trapping exits, the built-in handler from gen_server will invoke the terminate/2 callback with the reason. (more info)

(the above is summarized from The many and varied ways to kill an OTP Process | The log of Paul Wilson )

The idiomatic sequence implemented by terminate_child in DynamicSupervisor and Supervisor is:

• Process.exit(pid, :shutdown)
• wait for the :DOWN message
• if it doesn’t arrive (default in 5s), Process.exit(pid, :kill)

Prefer using those functions over building custom Process.exit setups unless you have a real good reason.

Re: reanimating processes - restart: :transient will restart the process if it exits with a reason other than :normal, :shutdown, or {:shutdown, term()} - for instance, if the process doesn’t respond to the :shutdown signal and gets killed. If that’s undesirable, consider restart: :temporary instead.

One final note: pay close attention to the gotchas listed in the terminate callback’s documentation. If you need a 100% reliable “GenServer went away” hook, consider using Process.monitor and handling the {:DOWN, ...} message.

Have you tried using DynamicSupervisor.terminate_child/2?

If you’re stopping a transient child cleanly then it should not be restarted.