Supervision Trees - A Beginner Writes

Gordon Guthrie, BTP, BT, SE <>
Thu Jan 15 12:05:54 CET 2004


Folks

I am writing my first supervision tree. I have an application which starts a
simple one-for-one supervisor.

This supervisor starts workers. The intention is that each worker will
eventually handle an http session, so I am starting them as transients.
These processes will die when the user session they support times out, so
each worker spawns a linked timeout process which periodically messages its
worker "if you haven't done anything since last time then exit".

The problem I have is that when the worker exits (either normal or a custom
timeout message) the supervisor and then the application both exit.

I can see that there might be circumstances that would kill a worker in
which a supervisor might also want to terminate for a clean restart.

So my question is how do I (under OTP) handle the exit message that results
from the spawn_link to the child. In a 'homebrew' supervision tree (ie last
week) I would have just trapped exits...

Ta

Gordon



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