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[bitnami/pgbouncer] Document how to connect PgBouncer with N PostgreSQL (#52229) 

[bitnami/pgbouncer] Document how to connect PgBouncer with N PostgreSQL servers

Signed-off-by: Gonzalo Gomez Gracia <gonzalog@vmware.com>
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Gonzalo Gómez Gracia 2023-10-30 12:02:24 +01:00 committed by GitHub
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@ -89,6 +89,8 @@ The Bitnami PgBouncer container requires a running PostgreSQL installation to co
* `PGBOUNCER_SET_DATABASE_USER`: Whether to include the backend PostgreSQL username in the database string. Default **no**.
* `PGBOUNCER_SET_DATABASE_PASSWORD`: Whether to include the backend PostgreSQL password in the database string. Default **no**.
* `PGBOUNCER_CONNECT_QUERY`: Query which will be executed after a connection is established. No Defaults.
* `PGBOUNCER_DSN_${i}`: PgBouncer configuration string for extra PostgreSQL server, where `i` is a number starting at zero (`0`).
* `PGBOUNCER_USERLIST_FILE`: Custom PgBouncer userlists file with connection credentials for any extra PostgreSQL backend. Required line format (including quotes): `"<postresql-user>" "<password>"`.
### Port and address binding
@ -275,6 +277,79 @@ docker-compose restart pgbouncer
Refer to the [server configuration](https://www.pgbouncer.org/usage.html) manual for the complete list of configuration options.
### How to connect with multiple PostgreSQL servers
It is possible to connect a single PgBouncer instance with multiple PostgreSQL backends. By using as many `PGBOUNCER_DSN_${i}` environment variables (with `i` starting at zero, `0`) as needed, and the `PGBOUNCER_USERLIST_FILE` variable pointing to a mounted volume with the required credentials for any extra PostgreSQL database in the format `"<postgresql-user>" "<password>"`.
The PgBouncer initialization process requires one PostgreSQL backend to be configured using the different `POSTGRESQL_*` variables listed in the [backend PostgreSQL connection](#backend-postgresql-connection), but the rest of backends connections can be provided using the method explained in this section. An example `docker-compose.yaml` for this scenario can be found below
```yaml
pg1:
image: docker.io/bitnami/postgresql:14
volumes:
- 'pg1_data:/bitnami/postgresql'
environment:
- POSTGRESQL_PASSWORD=password1
- POSTGRESQL_DATABASE=db1
pg2:
image: docker.io/bitnami/postgresql:15
volumes:
- 'pg2_data:/bitnami/postgresql'
environment:
- POSTGRESQL_PASSWORD=password2
- POSTGRESQL_DATABASE=db2
pg3:
image: docker.io/bitnami/postgresql:14
volumes:
- 'pg3_data:/bitnami/postgresql'
environment:
- POSTGRESQL_PASSWORD=password3
- POSTGRESQL_DATABASE=db3
pgbouncer:
image: docker.io/bitnami/pgbouncer:1
ports:
- 6432:6432
volumes:
- './userlists.txt:/bitnami/userlists.txt'
environment:
- POSTGRESQL_HOST=pg1
- POSTGRESQL_PASSWORD=password1
- POSTGRESQL_DATABASE=db1
- PGBOUNCER_AUTH_TYPE=trust
- PGBOUNCER_USERLIST_FILE=/bitnami/userlists.txt
- PGBOUNCER_DSN_0=pg1=host=pg1 port=5432 dbname=db1
- PGBOUNCER_DSN_1=pg2=host=pg2 port=5432 dbname=db2
- PGBOUNCER_DSN_2=pg3=host=pg3 port=5432 dbname=db3
volumes:
pg1_data:
driver: local
pg2_data:
driver: local
pg3_data:
driver: local
```
And this is the content of the `userlists.txt` file:
```text
"postgres" "password1"
"postgres" "password2"
"postgres" "password3"
```
Once initialized, the scenario above provides access to three diferent PostgreSQL backends from a single PgBouncer instance. As an example, you can request the PostgreSQL version of the backend server number two (notice it is the only running PostgreSQL 15.x in this scenario):
```bash
$ docker exec -it -u root debian-11-pgbouncer-1 psql -p 6432 -U postgres pg2 -c "show server_version;"
server_version
----------------
15.4
(1 row)
```
## Contributing
We'd love for you to contribute to this container. You can request new features by creating an [issue](https://github.com/bitnami/containers/issues) or submitting a [pull request](https://github.com/bitnami/containers/pulls) with your contribution.