Hi all,
Anyone experienced similar patterns on their Web-DB setups ?
Short setup description :
X frontend webservers (Apache 1.3.x) with php and mod_perl dynamic content.
1 backend db server (Postgresql 7.1.3).
The webservers are _very_ busy, but send only a limited amount of their
requests to the backend (most requests are served using static content).
Every now and then postgresql gets "too busy" and these patterns emerge :
- some connections are just idling and not being reaped (presumably either the
browser/client or the apache webserver timed out the request)
- these connections stack up to a point where the other "live" queries are
handled so inefficiently that pgsql enters a "bad downwards spiral".
(Meaning it cannot serve enough requests fast enough due to high load. The
number of connections increases, giving again more load, and so on ... )
I do VACUUM every night, and with Postgresql 7.1.3 cannot VACUUM during daily
usage.
I know upgrading to the 7.2 series is a sane way out (possibly) of this, but
due to development reasons, cannot do that right now (tm). I have to wait at
least another month or so..
Any clues to possible fixes / workarounds ?
Timeout settings someplace ?
BTW: The server has 1GB RAM, which seems sufficient to loading the entire DB
dataset into memory, disk issues should not be a performance hindering factor
here.
cheers!
--
Denis