# Bus Alt Connection

This module makes it possible to use PgBouncer as a connection pooler for odoo.

# 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.

# Why is this module needed?

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 mechanism from pg, 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 (here), we need odoo to connect directly to the pg server, bypassing PgBouncer.

That’s what this module implements, by overriding the relevant method of the Dispatcher.

Table of contents

# Installation

You don’t need to install this module in the database(s) to enable it.

But you need to load it server-wide:

- By starting Odoo with `--load=web,bus_alt_connection`
- Or by updating its configuration file:

    [options]
    (...)
    server_wide_modules = web,bus_alt_connection

# Configuration

You need to define how to connect directly to the database:

- Either by defining environment variables:

  > - `IMDISPATCHER_DB_HOST=db-01`
  > - `IMDISPATCHER_DB_PORT=5432`

- Or in Odoo’s configuration file:

    [options]
    (...)
    imdispatcher_db_host = db-01
    imdispatcher_db_port = 5432

# Bug Tracker

Bugs are tracked on GitHub Issues. In case of trouble, please check there if your issue has already been reported. If you spotted it first, help us to smash it by providing a detailed and welcomed feedback.

Do not contact contributors directly about support or help with technical issues.

# Credits

## Authors

- Trobz

## Contributors

- Nils Hamerlinck <nils@trobz.com>

## Maintainers

This module is maintained by the OCA.

OCA, or the Odoo Community Association, is a nonprofit organization whose mission is to support the collaborative development of Odoo features and promote its widespread use.

This module is part of the OCA/server-tools project on GitHub.

You are welcome to contribute. To learn how please visit https://odoo-community.org/page/Contribute.