[Pgpool-general] Replication and number of postgres processes

[Tatsuo Ishii]

>From pgpool doc:

  <dt>max_pool</dt>
  <dd>
      <p>The maximum number of cached connections in pgpool-II
      children processes. pgpool-II reuses the cached connection if an
      incoming connection is connecting to the same database with the
      same username. If not, pgpool-II creates a new connection to the
      backend. If the number of cached connections exceeds max_pool,
      the oldest connection will be discarded, and uses that slot for
      the new connection.

max_pool is only related to number of username/database combo. Say,
you have 2 combos (for example, "user1/mydb" and "user2/mydb") you can
assumes it as a constant 2 in the fomula repsented in the pgpool doc.

max_pool*num_init_children <= (max_connections - superuser_reserved_connections) (no query canceling needed)
max_pool*num_init_children*2 <= (max_connections - superuser_reserved_connections) (query canceling nee

BTW  I'm not sure what you mean by "replication servers".
--
Tatsuo Ishii
SRA OSS, Inc. Japan
English: http://www.sraoss.co.jp/index_en.php
Japanese: http://www.sraoss.co.jp

> Yes, I've seen that, but going from 3 (physical) replication servers to 5
> replication servers, would I need to increase max_pool in that formula from
> 4 to 6? Or a more extreme example would going from 2 replication servers to
> 128 with an expected 100 simultaneous "UPDATE" queries on each server result
> in going from 200 postgres-connections on each server to 12800
> postgres-connections on each server?
> 
>>From my experiment with 3 servers it looked like the need for connections on
> each server would increase when I add servers. I just want to make sure that
> is the right conclusion before making a decision on how to use pgpool.
> 
> Regars
> John Andre Taule
> 
> -----Original Message-----
> From: Tatsuo Ishii [mailto:ishii at sraoss.co.jp] 
> Sent: 24. januar 2011 08:39
> To: post at johnandre.net
> Cc: pgpool-general at pgfoundry.org
> Subject: Re: [Pgpool-general] Replication and number of postgres processes
> 
> There is a formula for this in the pgpool documentation.
> See the "num_init_children" section.
> --
> Tatsuo Ishii
> SRA OSS, Inc. Japan
> English: http://www.sraoss.co.jp/index_en.php
> Japanese: http://www.sraoss.co.jp
> 
>> Will the number of postgres processes needed increase by how many 
>> servers is used for replication?
>> Example 100 connections by the frontend application.
>> 2 replication servers: 200 connections
>> 3 replication servers: 300 connections
>> N replication servers: n*100 connections
>> Is my understanding of resources needed correct?
>> Regards
>> John Andre Taule
>> 
>