04-10-2010
collectl - your one-stop tool
I just answered a previous note about memory usage and pointed the user at collectl. There are a couple of things worth noting - collectl is VERY lightweight, on the order of using <0.1% of the cpu when sampling system data every 10 seconds! When trying to track down something tricky you ALWAYS need fine grained time or you never see those spikes that so ofter offer at the least expected time. In fact if you want to sample once a second you're still <1%.
But back to the problem at hand. While you can certainly run ps from cron every hours there are 2 reasons why you might not want to. First of all, sampling once an hour isn't really going to help much unless you get real lucky. Second, even if ps did tell you something you might also want to get other things that happened at the time in question like CPU, memory usage, open files, etc. but you don't have access to it because you didn't think to ask ahead of time.
With collectl, you just start it running as a daemon and it will collect more than you thought of to ask. It will even collect info on your slab usage and a runaway allocation of slab memory can certainly trigger the out-of-memory killer.
Just note that collectl only monitors slabs/processes once a minute because there are high load tasks...
-mark
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LEARN ABOUT CENTOS
doveadm-log
DOVEADM-LOG(1) Dovecot DOVEADM-LOG(1)
NAME
doveadm-log - Locate, test or reopen Dovecot's log files
SYNOPSIS
doveadm [-Dv] log errors [-s min_timestamp]
doveadm [-Dv] log find [directory]
doveadm [-Dv] log reopen
doveadm [-Dv] log test
DESCRIPTION
The doveadm log commands are used to locate and reopen the log files of dovecot(1). It's also possible to test the configured targets of
the *log_path settings.
OPTIONS
Global doveadm(1) options:
-D Enables verbosity and debug messages.
-v Enables verbosity, including progress counter.
COMMANDS
log errors
doveadm log errors [-s min_timestamp]
The log errors command is used to show the last - up to 1,000 - errors and warnings. If no output is generated, no errors have occurred
since the last start.
-s min_timestamp
An integer value, representing seconds since the epoch - also known as Unix timestamp. When a min_timestamp was given, doveadm(1)
will only show errors occurred since that point in time.
log find
doveadm log find [directory]
The log find command is used to show the location of the log files, to which dovecot(1) sends its log messages. If dovecot(1) logs its
messages through syslogd(8) and doveadm(1) could not find any log files, you can specify the directory where your syslogd writes its log
files.
log reopen
doveadm log reopen
This command causes doveadm to reopen all log files, configured in the log_path, info_log_path and debug_log_path settings. These settings
are configured in /etc/dovecot/conf.d/10-logging.conf.
This is for example useful after manually rotating the log files.
log test
doveadm log test
This command causes doveadm to write the message "This is Dovecot's priority log (timestamp)" to the configured log files. The used prior-
ities are: debug, info, warning, error and fatal.
EXAMPLE
This example shows how to locate the log files used by dovecot(1).
doveadm log find
Looking for log files from /var/log
Debug: /var/log/dovecot.debug
Info: /var/log/mail.log
Warning: /var/log/mail.log
Error: /var/log/mail.log
Fatal: /var/log/mail.log
REPORTING BUGS
Report bugs, including doveconf -n output, to the Dovecot Mailing List <dovecot@dovecot.org>. Information about reporting bugs is avail-
able at: http://dovecot.org/bugreport.html
SEE ALSO
doveadm(1)
Dovecot v2.2 2013-11-24 DOVEADM-LOG(1)