[syslog-ng] syslog-ng uses 100% cpu when i use program() destination driver

Fegan, Joe Joe.Fegan at hp.com
Wed Dec 10 12:23:34 CET 2008

Hi Scott,

100% cpu usage for an indefinite period after some event is the stereotypical symptom of an infinite loop in the event handler. And I can see exactly the cause of this loop in your "program" statement - it's a classic error that has been discussed on this list many times before. You should find good information about it in the archives - look for discussions of the "program" statement.

In a nutshell: A syslog-ng "program" script is not permitted to exit after each message, it is required to read a series of individual messsages from its stdin and act on each one separately. If you write a script that exits after processing one message, it will cause exactly the sort of infinite loop you describe here. What's happening is that your script exits, syslog-ng starts it again, it exits again, syslog-ng starts it again, it exits again, syslog-ng starts it again, it exits again, syslog-ng starts it again, and on and on and on.

See the syslog-ng docs and previous posts to this list for information on how the script behind a "program" destination is required to work.


-----Original Message-----
From: syslog-ng-bounces at lists.balabit.hu [mailto:syslog-ng-bounces at lists.balabit.hu] On Behalf Of Scott McGillivray
Sent: 10 December 2008 10:48
To: syslog-ng at lists.balabit.hu
Subject: [syslog-ng] syslog-ng uses 100% cpu when i use program() destination driver

Hi all,

I have installed syslog-ng via apt-get on an Ubuntu 8.10 server.

I have added the below to the configuration file:

template t_smtp {
HELO localhost
MAIL From: admin at example.com
RCPT To: scott at example.com
From: admin at example.com
To: scott at example.com
Subject: Syslog msg from $HOST - [$FACILITY:$PRIORITY] $PROGRAM


log {

destination d_logfile {
        program("sendmail -bs > /var/log/syslog-email.log 2>&1"

For some reason with the above config after a message hits d_logfile the
CPU usage jumps to 100% and stays there until syslog-ng is stopped. It's
like some file it uses during the process gets locked and the thing jams
up waiting forever.

The only way to solve the problem is remove the program() entry and
replace it with file("/var/log/temp.log" template(t_smtp)); in which
case it works fine.

To test the program()destination I created a php script that just slept
for 10 seconds


And called it in d_logfile { } with program("/usr/bin/php

And sure enough the cpu jumped to 100% and stayed there until syslog-ng
was stopped.

Can anyone see a program with my above config or suggest why syslog-ng
can't cope when the program() doesn't return immediately?


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