[pgpool-general: 6836] NOTIFY/LISTEN delay explanation?

[Holger Jahn]

Hi there,

Just installed PgPool 4.1.0 from sources today (with SSL enabled). Using it against PostgreSQL 12.1 
on Arch Linux.

The PgPool configuration is a straight raw setup copied from the pgpool.conf.sample. Nothing fancy, 
just testing connection pooling.

Here is my question.

I have some rules in PG which respond to UPDATE/INSERT/DELETE to one particular table and send 
NOTIFY messages to connected apps. When all these apps are connected straight to Postgres (!), and 
some app is making changes to this table, then a NOTIFY is triggered and sent and received by all 
connected apps instantly. Literally, all happening at once.

However, if the same apps are connected to PgPool, instead of straight to Postgres, then there is a 
delay of about 3-5 seconds between making a modification and the reception of the database NOTIFY.

Now, from an app/deployment standpoint I am perfectly fine with that, but I would like to satisfy my 
curiosity as to WHY there is such a delay. I studied the config file settings, but I can not find 
any option that could relate to this and/or explain what is going on.

Anybody out there who can shed some light?

Many thanks,

Holger