Using PgBouncer with Odoo

In Odoo

PgBouncer is as a connection pooler for PostgreSQL. Is is useful in Odoo deployments, especially when there is a big number of users and Odoo workers involved.

Why isn't odoo's connection pooling good enough?

Odoo's builtin connection pooling works at process level: each Odoo process has its own ConnectionPool, limited to db_maxconn.

It does the job of re-using open connections available in the pool. But it never closes these connections, unless reaching db_maxconn.

In practice, we observe that each odoo worker will end up with up to 3 open connection in its pool. With 10 http workers, that's up to 30 connection continuously open just for one single instance.

Here comes PgBouncer

PgBouncer will help to limit this number of open connections, by sharing a pool of connections at the instance level, between all workers. Odoo workers will still have up to 3 open connections, but these will be connections to PgBouncer, that on its side will close unnecessary connections to pg.

This has proven to help performances on Odoo deployments with multiple instances.

It allows you to define how resources should be shared, according to your priorities, e.g. :

  • key odoo instance on host A can open up to 30 connections
  • while odoo instance on host B, dedicated to reports, can open up to 10 connections only

And most importantly, it helps you to ensure that max_connections will never be reached on pg server side.

Some changes are needed to make Odoo work with PgBouncer

When configuring PgBouncer, you can choose between 2 transaction pooling modes:

  • pool_mode = session
  • pool_mode = transaction

If we choose pool_mode = session, then one server connection will be tied to a given odoo process until its death, which is exactly what we're trying to change. Thus, to release the server connection once the transaction is complete, we use pool_mode = transaction.

This works fine, except for Odoo's longpolling features that relies on the LISTEN/NOTIFY, which is not compatible with that mode.

To be more precise, NOTIFY statements are properly transfered by PgBouncer in that mode; only the LISTEN statement isn't (because it needs to keep the server connection open).

So for the unique "listening" connection per instance that requires this statement, we need odoo to connect directly to the pg server, bypassing PgBouncer.

A new module is born: bus_alt_connection

At Trobz we created bus_alt_connection to implement these needed changes, by overriding the relevant method of the Dispatcher.

This module has been used successfully in production for months. We recently open sourced it by pushing it to OCA/server-tools. If you're willing to use PgBouncer in your Odoo deployment(s), you should give it a try, feedbacks/reviews welcome!