[pgpool-general: 4658] Pgpool hanging

Dominic Binks dominic.binks at audioanalytic.com
Wed Apr 27 19:09:59 JST 2016


I'm looking for some clue as to what's going on with my configuration of pgpool.  I'm sure I've just got some of the parameters wrong but I've played for a bit and not got it working acceptably.

My set up is based on AWS infrastructure:

Two RDS database instances (in different regions) - one of which is nominated as primary, the other as secondary
Pgpool running on hosts in each region talking to both servers

In each region there are clients talking to their respective local pgpool.

In order to build the infrastructure I run a few SQL scripts to initialise the database structures and load some data in to the databases.

I then run our unit tests against the local pgpool instances on each of the two hosts (though not at the same time).

What I find is that pgpool will service a number of connections and then hang.  I found some information on hanging and a command to dump the TCP stats which would show the number of requests queuing but I do not see this.

The RDS instances have a limited number of user connections (16).  My two servers currently make 6 connections from each region (so I'm currently using 12 connections against a single RDS instance).

I don't mind if pgpool has the ability to server more connections but while it's going into this hanging state I clearly can't put it into production.

Can anyone shed some light on why pgpool is hanging like this?  What precisely is the relationship between the number of backend connections to databases and the front end client connections?  Is it better to have the backend connections reuse existing connections or reconnect per client?

Many thanks for any information you can give.


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