[users@httpd] Spawned process doesn't get termination signal in worker MPM

[Phil Endecott <sp...@chezphil.org>]

Dear List,

I have an Apache2 module that forks a new process when it first handles 
a request. Subsequent request-handling processes/threads communicate 
with this "back-end" process via shared memory.  This generally works, 
but I am having trouble at termination.  It seems that my backend 
process terminates when I'm using the "prefork" MPM, but not when I'm 
using "worker".

As far as I can see, in the "prefork" environment my process gets 
SIGTERM, which it handles (it needs to delete its shared memory segment) 
and then exits.  In the "worker" environment it looks as if it doesn't 
get any signal and becomes an oprphan, with init as its parent.  I find 
it odd that it gets SIGTERM - has Apache sent it? - normally it would 
get SIGHUP from the kernel when its process group leader terminates.  I 
guess that Apache is trying to kill its children itself, rather than 
letting the kernel do it, and is behaving differently in the two MPMs. 
But I have not told Apache anything about this process - how did it find 
its pid?

Doe this makes any sense to anyone?  I note that 2.1 has had some 
changes to shutdown; is this related?

This code is for Anyterm - http://anyterm.org/ - and you can see the 
code for the backend process at 
http://svn.anyterm.org/anyterm/trunk/apachemod/backend.cc.  The relevant 
bits are at the end of the file.

I'm using 2.0.54 on Debian.

Sorry this is a bit vague.  I'm just hoping someone will immediately 
recognise what's going wrong....

Cheers,

--Phil.


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