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Could you please explain a warning message

Yesterday I saw the following warning message in my logs:-

2018-10-06T14:11:19+01:00 geronimo postfix/postscreen[8194]: warning: psc_cache_update:
btree:/var/lib/postfix/postscreen_cache update average delay is 151 ms

A tenth of a second is an ENORMOUS delay for an SSD, and my immediate thought was/is an incipient disc failure, but
the monthly disc tests say 95 percent of the life expectancy remains.

I have swept my logs since February and this is the only instance of the message.

I am operating a domestic server (50 messages a day), running on a Synology NAS device, with things in the background
I can't turn off.

Could someone please explain what this message implies.

Many thanks

Allen C

Perhaps I should get some back-ups done :-)

Comments

Re: Could you please explain a warning message

By Ralf Hildebrandt at 10/08/2018 - 07:03

* Allen Coates < ... at cidercounty dot org.uk>:
Oct 2 02:01:40 mail-cbf postfix/postscreen[23257]: warning: psc_cache_update: btree:/var/lib/postfix/postscreen_cache update average delay is 343 ms
Oct 2 02:03:16 mail-cbf postfix/postscreen[23257]: warning: psc_cache_update: btree:/var/lib/postfix/postscreen_cache update average delay is 155 ms
Oct 3 18:34:07 mail-cbf postfix/postscreen[23257]: warning: psc_cache_update: btree:/var/lib/postfix/postscreen_cache update average delay is 137 ms
Oct 8 11:21:19 mail-cbf postfix/postscreen[65199]: warning: psc_cache_update: btree:/var/lib/postfix/postscreen_cache update average delay is 112 ms

Quoting from <a href="http://postfix.1071664.n5.nabble.com/psc-cache-update-td10059.html" title="http://postfix.1071664.n5.nabble.com/psc-cache-update-td10059.html">http://postfix.1071664.n5.nabble.com/psc-cache-update-td10059.html</a>

"It is a bit sluggish. The warning threshold is 100ms. It should not
take this long to insert one key/pair into the database. Perhaps your
system's disk is very busy, or you're on a VM slice, or your clock is
not stable. If this happens frequently you need to find out why."

and

"If this happens often, this means that postscreen cannot handle
more than 10 SMTP connections per second, or that your system clock
is jumping (as in: running inside a VM).

I see the warning once a day on my lightly-loaded server with a
single 15kRPM disk under an ancient CPU; the timing suggests that
this happens while some cron job is doing house cleaning.

I added this check because someone insisted on running postscreen
on top of an SQL database, and complained that postscreen performance
was erratic. After I added the warning he stopped complaining."