On Thu, 28 Jun 2001, Andrej Borsenkow wrote:
got 10K duplicated messages. Reason was, I use procmail as mda and fetchmail
believed it exited with error and tried to fetch the same messages over and
over again.
One of our users also reported this. It's filled as Debian Bug#102711;
Thanks for tracking down the problem.
Comparing with 5.8.0, the reason seems to be changed SIGCHLD handling. 5.8.0
reset SIGCHLD to SIG_DFL after successful popen(). 5.8.10 always has it
cought and processed by sigchld_handler. But sigchld_handler() reaps away
exited mda process, so that pclose() gets an error trying to get status and
returns an error.
So THAT's what tthat sig_dfl thing did. It was creating heaps of zombies,
and since I could not find what it was used for AND Eric didn't recall it
either, it was removed. Eric, let's document WHY that stuff exists when it
is added back :P
Apparently, SIGCHLD set to SIG_DFL must be done IFF fetchmail is delivering
to a MDA, but the docs should warn that zombies will not be reaped until the
run is finished, and that WILL cause resource starvation if plugins are
being used and too many zombies accumulate.
Bottom line: either don't deliver to a MDA using plugins, or risk being
overrun by an army of undead.
--
"One disk to rule them all, One disk to find them. One disk to bring
them all and in the darkness grind them. In the Land of Redmond
where the shadows lie." -- The Silicon Valley Tarot
Henrique Holschuh