imapd's hang when maxchild count is reached

[Lawrence Greenfield]

   From: "Stephen L. Ulmer" <ulmer at ufl.edu>
   Date: Wed, 05 Feb 2003 16:57:15 -0500
[...]
   Hmmm... what does Sendmail do?  It's got lots of children, but still
   manages to refuse connections when it gets busy (RefuseLA)...  I kinda
   like that behavior.  I definitely like it better than keeping more and
   more sockets open.

Sendmail only accepts new connections in the parent process. When the
LA goes over RefuseLA, it closes the socket. In order to reopen the
socket, the parent always has root privs. (The cyrus master process
changes to "cyrus" from "root" very early on.)

So Sendmail's scheme doesn't work for us. I took a look at a random
version of Postfix, and I'm pretty sure it does what we do now (build
up the system listen queue).

I also agree that it's more user friendly to quickly deny
service. I contemplated having a special child to deny service
(something like what Ohio has implemented) but it seems
tricky. (Imagine the # of processes bouncing right next to the limit.)
I definitely would like to avoid forking for every new connection once
we're over the limit, since that will just strain the system after
we're already heavily loaded.

Larry