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diff --git a/doc/administration/postgresql/pgbouncer.md b/doc/administration/postgresql/pgbouncer.md index 4f9056b9b50..7171e90949e 100644 --- a/doc/administration/postgresql/pgbouncer.md +++ b/doc/administration/postgresql/pgbouncer.md @@ -200,6 +200,45 @@ Once you've performed the tasks or procedure, switch back to using PgBouncer: sudo gitlab-ctl reconfigure ``` +## Fine tuning + +PgBouncer's default settings suit the majority of installations. +In specific cases you may want to change the performance-specific and resource-specific variables to either increase possible +throughput or to limit resource utilization that could cause memory exhaustion on the database. + +You can find the parameters and respective documentation on the [official PgBouncer documentation](https://www.pgbouncer.org/config.html). +Listed below are the most relevant ones and their defaults on an Omnibus GitLab installation: + +- `pgbouncer['max_client_conn']` (default: `2048`, depends on server file descriptor limits) + This is the "frontend" pool in PgBouncer: connections from Rails to PgBouncer. +- `pgbouncer['default_pool_size']` (default: `100`) + This is the "backend" pool in PgBouncer: connections from PgBouncer to the database. + +The ideal number for `default_pool_size` must be enough to handle all provisioned services that need to access +the database. Each of the listed services below use the following formula to define database pool size: + +- `puma` : `max_threads + headroom` (default `14`) + - `max_threads` is configured via: `gitlab['puma']['max_threads']` (default: `4`) + - `headroom` can be configured via `DB_POOL_HEADROOM` env variable (default to `10`) +- `sidekiq` : `max_concurrency + 1 + headroom` (default: `61`) + - `max_concurrency` is configured via: `sidekiq['max_concurrency']` (default: `50`) + - `headroom` can be configured via `DB_POOL_HEADROOM` env variable (default to `10`) +- `geo-logcursor`: `1+headroom` (default: `11`) + - `headroom` can be configured via `DB_POOL_HEADROOM` env variable (default to `10`) + +To calculate the `default_pool_size`, multiply the number of instances of `puma`, `sidekiq` and `geo-logcursor` by the +number of connections each can consume as per listed above. The total will be the suggested `default_pool_size`. + +If you are using more than one PgBouncer with an internal Load Balancer, you may be able to divide the +`default_pool_size` by the number of instances to guarantee an evenly distributed load between them. + +The `pgbouncer['max_client_conn']` is the hard-limit of connections PgBouncer can accept. It's unlikely you will need +to change this. If you are hitting that limit, you may want to consider adding additional PgBouncers with an internal +Load Balancer. + +When setting up the limits for a PgBouncer that points to the Geo Tracking Database, +you can likely ignore `puma` from the equation, as it is only accessing that database sporadically. + ## Troubleshooting In case you are experiencing any issues connecting through PgBouncer, the first |