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Dec 1, 2022
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Add docs explaining max postgres connections #1182

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Add docs explaining max postgres connections
spikecurtis Nov 30, 2022
ab931e1
Fix typo
spikecurtis Nov 30, 2022
0f7e102
Fix broken link
spikecurtis Nov 30, 2022
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28 changes: 28 additions & 0 deletions guides/deployments/postgres.md
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Expand Up @@ -131,3 +131,31 @@ If the upgrade fails for any reason, please run the `helm rollback` command and

Once you complete this process, you'll be able to access Coder using the
external IP address of the ingress controller in your cluster.

### Scaling Coder & PostgreSQL

Each Coder replica maintains a pool of connections to Postgres, capped at a
maximum of 30 connections by default. This value strikes a balance between
allowing multiple concurrent requests and using up connections on the Postgres
database.

To reconfigure this value, set the environment variable
`CODER_MAX_DB_CONNECTIONS` to your desired value in the `coderd.extraEnvs`
section of the Helm chart.

> **Important**: You must ensure that Coder's maximum connections per replica
> times the number of Coder replicas is less than the maximum number of
> connections your Postgres instance allows, assuming Coder is the only
> application using the Postgres instance (less if other applications will also
> consume connections). For example, with 3 Coder replicas and the default max
> connections of 30, you must ensure Postgres is configured to allow 90
> connections. If Postgres runs out of connections Coder may fail API requests
> or builds.

By default, Postgres allows a maximum of 100 open connections (less 3 reserved
for superusers). Consult
[Postgres documentation](https://www.postgresql.org/docs/12/runtime-config-connection.html),
or your database administrator for information on how to change this value.

Consider monitoring the [`go_sql_open_connections`](../../admin/prometheus.md)
metric to see how many connections Coder uses in different load scenarios.