Thread: Why i see several postgres server processes sometimes ?

Why i see several postgres server processes sometimes ?

From

Georgi Ivanov

Date:

06 October 2010, 14:44:43

Hi,
I wander why i see several postgres server processes with different PIDs
I don't mean those normal query processes. I see several of these:
/usr/lib/postgresql/8.4/bin/postgres -D /database/postgresql/8.4/main -c config_file=/etc/postgresql/8.4/main/postgresql.conf
With different pids. Is this normal ?

PID USER      PR NI VIRT RES SHR S %CPU %MEM    TIME+ COMMAND
27662 postgres 20   0 1623m 14m 10m R    5 0.3   0:00.14 postgres: wmg wmg 172.18.9.21(43725) idle
15489 postgres 20   0 1610m 33m 33m S    3 0.7 76:51.46 /usr/lib/postgresql/8.4/bin/postgres -D /database/postgresql/8.4/main -c config_file=/etc/postgresql/8.4/main/postgresql.conf
27714 postgres 20   0 1613m 7720 5228 S    1 0.2   0:00.03 postgres: wmg wmg 172.18.9.12(42434) idle
27730 postgres 20   0 1611m 2336 1228 R    1 0.0   0:00.02 /usr/lib/postgresql/8.4/bin/postgres -D /database/postgresql/8.4/main -c config_file=/etc/postgresql/8.4/main/postgresql.conf
27731 postgres 20   0 1610m 1572 1044 R    1 0.0   0:00.02 /usr/lib/postgresql/8.4/bin/postgres -D /database/postgresql/8.4/main -c config_file=/etc/postgresql/8.4/main/postgresql.conf
15494 postgres 20   0 1611m 1.5g 1.5g S    0 30.6   6:10.54 postgres: writer process
27711 postgres 20   0 1613m 7752 5248 S    0 0.2   0:00.01 postgres: wmg wmg 172.18.9.13(53169) idle
27729 postgres 20   0 1610m 1572 1044 R    0 0.0   0:00.01 /usr/lib/postgresql/8.4/bin/postgres -D /database/postgresql/8.4/main -c config_file=/etc/postgresql/8.4/main/postgresql.conf
15495 postgres 20   0 1611m 1020 652 S    0 0.0   0:23.09 postgres: wal writer process
15496 postgres 20   0 1612m 1648 564 S    0 0.0   0:24.77 postgres: autovacuum launcher process
15497 postgres 20   0 73524 1308 296 S    0 0.0 18:29.63 postgres: stats collector process
17480 postgres 20   0 37052 940 936 S    0 0.0   0:00.01 su postgres
17481 postgres 20   0 19384 1236 1232 S    0 0.0   0:00.01 bash
17510 postgres 20   0 67696 2400 1992 S    0 0.0   0:00.12 /usr/lib/postgresql/8.4/bin/psql wmg
17537 postgres 20   0 1617m 26m 21m S    0 0.5   0:00.12 postgres: postgres wmg [local] idle
27722 postgres 20   0 1614m 10m 7372 R    0 0.2   0:00.00 postgres: wmg wmg 172.18.9.13(53195) idle
27724 postgres 20   0 1613m 7700 5208 R    0 0.2   0:00.00 postgres: wmg wmg 172.18.9.12(42452) PARSE
27727 postgres 20   0 1613m 4324 2336 R    0 0.1   0:00.00 postgres: wmg wmg 172.18.9.13(53204) startup
27732 postgres 20   0 1610m 424    0 R    0 0.0   0:00.00 /usr/lib/postgresql/8.4/bin/postgres -D /database/postgresql/8.4/main -c config_file=/etc/postgresql/8.4/main/postgresql.conf
27733 postgres 20   0 1610m 424    0 R    0 0.0   0:00.00 /usr/lib/postgresql/8.4/bin/postgres -D /database/postgresql/8.4/main -c config_file=/etc/postgresql/8.4/main/postgresql.conf

Re: Why i see several postgres server processes sometimes ?

From

Peter Geoghegan

Date:

06 October 2010, 17:36:33

On 6 October 2010 15:44, Georgi Ivanov <georgi.r.ivanov@gmail.com> wrote:
> Hi,
> I wander why i see several postgres server processes with different PIDs
> I don't mean those normal query processes. I see several of these:
> /usr/lib/postgresql/8.4/bin/postgres -D /database/postgresql/8.4/main -c
> config_file=/etc/postgresql/8.4/main/postgresql.conf
> With different pids. Is this normal ?
>

This is normal. Postgres is said to have a multi-process architecture
(which is often contrasted with a multi threaded architecture). The
number of processes isn't very predictable.


--
Regards,
Peter Geoghegan

Re: Why i see several postgres server processes sometimes ?

From

"Massa, Harald Armin"

Date:

06 October 2010, 17:53:46

Peter,

This is normal. Postgres is said to have a multi-process architecture
(which is often contrasted with a multi threaded architecture). The
number of processes isn't very predictable.

you are right, it is normal.

But the number of processes is quite predictable:

on default PostgreSQL starts up with 5 processes:

one background-writer

one postmaster who masters the startup of additional progresses

one autovacuum-daemon

two processes which I have not leveled up enough to know what they are doing

And then there is one additional process for every client connection.

Harald

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Harald Armin Massa
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Re: Why i see several postgres server processes sometimes ?

From

Raymond O'Donnell

Date:

06 October 2010, 18:40:42

On 06/10/2010 18:53, Massa, Harald Armin wrote:
> Peter,
>
>     This is normal. Postgres is said to have a multi-process architecture
>     (which is often contrasted with a multi threaded architecture). The
>     number of processes isn't very predictable.
>
> you are right, it is normal.
>
> But the number of processes is quite predictable:
>
> on default PostgreSQL starts up with 5 processes:
>
> one background-writer
> one postmaster who masters the startup of additional progresses
> one autovacuum-daemon
> two processes which I have not leveled up enough to know what they are doing
> And then there is one additional process for every client connection.

So that's where the extra processes are coming from - something is
holding connections open.

Ray.

--
Raymond O'Donnell :: Galway :: Ireland
rod@iol.ie