On 11/28/2011 05:45 PM, Noel Jones wrote:
On 11/28/2011 1:04 PM, Wietse Venema wrote:
Alfredo Saldanha:
Dear,
I'd like to know if is there some way to disable automatic or manually
Postfix filters in case of failure (overload) or something.
I'm asking this because I was an incident where, under an overload of
messages, I had problems with my mx performance (very high CPU load and
memory usage) to deliver messages through filters header and body checks
and also a check for a policy server.
Somewhere in an overload, some messages were blocked, and would
certainly "whitelisted" the Policy Server, but it was no longer
responding to connections due to high load on the server processes.
Then ask them, is possible turn off or divert messages from filters like
cidr (check_client_access), body (body_checks) and header checks in the
event of an overload of messages?
First of all, you must configure the system such that Postfix can
handle the load for the configured SMTP server process limit. If
the default process limit (100) is too high for your system, reduce
the number.
http://www.postfix.org/postconf.5.html#default_process_limit
You can stress test Postfix performance with the smtp-source utility
which is included with Postfix source code.
http://www.postfix.org/smtp-source.1.html
Postfix has an overload-adaptive mechanism, but you should first
reduce your process limit until it is small enough that your system
can handle the load.
http://www.postfix.org/STRESS_README.html
Wietse
Alfredo,
In addition to what Wietse writes, I would encourage you to test
your system to see exactly what is failing under high load.
The check_client_access cidr table is unlikely to add more than a
negligible amount of CPU usage, although a very large table (10's of
thousands entries) might use quite a bit of memory. Access table
usage will show up in the memory and CPU usage of the smtpd
processes. Temporarily disable your access tables to measure the
impact on the smtpd processes -- and note that most of the memory
used by smtpd is shared between processes.
header_checks and body_checks likewise should not use much ram or
CPU unless you've configured an unreasonable number of checks.
Remove entries that rarely or never match anything; limit the amount
of data checked with body_checks by setting body_checks_size_limit
to some reasonable number (the default 51200 should be reasonable
for most sites). These checks are run by the cleanup processes.
Policy servers are a frequent source of performance issues. Make
sure yours isn't dying or timing out under heavy load.
Finally, if your machine is swapping due to high memory use, either
add RAM or reduce the postfix default_process_limit to manage peak
memory use.
-- Noel Jones
Hi,
I have 6 instances of postfix here, one of each filter, transport maps, etc.
My first instance is "default_process_limit = 550", I supose that it was
not measured, but anyway, I'll make the stress test using postfix-source
to be sure how is the best configuration.
I send news.
Thank you guys,
Alfredo
