[pgpool-general: 4491] Why so many backend connections?

Brandon Ridler brandonr at motiga.com
Thu Feb 25 11:18:30 JST 2016


I've scoured the site and the interwebs with out being able to find
information in regards to what I'm seeing and am hoping I can be pointed in
the right direction, or given an explanation as to why it appears every
connection to pgpool is resulting in a connection to every backend I have.
My general setup when compared to a default is:

1.  I have 3 backends, all weight 1.
2.  I have master/slave mode enabled with stream.
3.  I have load_balancing on.
4.  I have connection_cache off.
5.  I have connection_life_time set to 60.
6.  I have watchdog enabled and configured.

I'm using 3.5.0 pgpool2 running on an ubuntu 14.0.4 inside a docker
container.  I also tried 3.3.2 from the ubuntu apt repos.

It doesn't matter if it's our custom app, an established app like ejabberd,
or me using psql to connect to it, it will always make connections to all
backends listed.  I'd like to know if that is expected behavior but haven't
found anything in the docs to confirm or deny this other than a reference
to when your making transactions.

Assuming the above is correct, I tried to use the connection_life_time
value.  Thinking that if the front-end connection to pgpool is idle, and
thus the backend is idle, that at least pgpool would close the backend and
re-establish it if anything came down from the apps.

Can you please let me know if I'm misunderstanding the intent of pgpool
here or if there's a configuration that I may be overlooking.  I thought
when I originally set up pgpool a month ago that I saw like 300 connection
to pgpool and only 50-60 connections to each of the backends.

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