Richard Huxton wrote:
denis@xxxxxxxxxxx wrote:
We have a postgresql server configured with max_connections=4096.
We have such a high number of max_connections because there are 8 web
servers connected to the database and all use persistent connections.
Each web server can have 256 max clients and 2 connection strings, so
the max connections to the db is 256 * 8 * 2=4096.
The one-word answer is "pgpool" http://pgpool.projects.postgresql.org/
You don't really want them all using persistent connections directly
to the DB.
Already checked.
We set a machine with only pg_pool installed as a fronted to the real db.
If I disable persistent connections and I use pg_pool with 4096
preforked clients, the load of the pg_pool server goes very high and the
takes down also the real database server. Maybe should I try installing
pg_pool direcly into the database server to avoid network traffic?
To start the postgresql, I must to do some kernel extra configuration:
kernel.shmmax = 1165063808
kernel.sem=512 64000 100 512
and the parameters i changed other than max_connections in the
postgresql.conf are:
- shared_buffers = 131072
That's a *very* big shared_buffers value. Try reducing it by a factor
of 10 and reading the "performance tuning" article here:
http://www.varlena.com/varlena/GeneralBits/Tidbits/index.php
Already read. I put 25% of total memory as that specified by Bruce
Momjian performance howto but now i'm lowering 65536
Sounds like a BEGIN being re-issued alright. Solution - fix your
application(s) and don't use persistent connections (or if you do,
make sure you rollback any pre-existing transactions and issue any
relevant SET commands).
If that was the problem, I should obtain always that error but I obtain
that error only after two/three hours of testing.
Thank you for your help,
Denis
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