Re: [HACKERS] Postmaster options, process spawning, logging, etc.

Matthew Hagerty <matthew(at)venux(dot)net> writes:
> How many backend processes is considered a large number? The man pages
> says the default is 32. Does anyone set their number higher?

I've run test cases with 100, which is about as high as I can go on my
personal box without running out of swap space. I think some people
are using several hundred.

> Kind of related to the question above; when does the postmaster spawn
> another backend process? Is it for each additional connection,

Per connection. The backend quits when the client disconnects. Of
course, it's up to the client how long it stays connected or how many
queries it asks...

> The postmaster log file, why are the entries not datestamped?

Uncomment #define ELOG_TIMESTAMPS in include/config.h after configure
and before make...

> Also, what is the highest debug level and how big can I expect
> the log to grow? Can I rotate the log without stopping the postmaster?

Not very readily. There is someone working on using syslog logging,
which'd be a lot nicer than what we have.

> What is the pg_log file in the data directory?

Transaction commit data. Don't touch it ;-). It shouldn't be all that
big, though...

> What are the major system resources used by postgres, i.e. semaphores, file
> handles, mbufs, etc.? I'm trying to determine if I have my resources
> configured high enough for my user base.

In 6.5, the postmaster won't start up if you don't have enough
semaphores and shared memory. I've never heard of anyone running out of
file handles, but it certainly seems possible if you start enough
backends. Still, though, I wouldn't expect a hard coredump such as you
are getting from running out of any of these resources. There should at
least be something showing up in the postmaster log if we fail to open a
file or something like that...

regards, tom lane