How Conn limit works

Case descriptionCase description

You need to understand how the Conn limit parameter works in Managed Service for PostgreSQL.

SolutionSolution

Conn limit sets the maximum allowed number of connections per user. In session pooling, this setting limits the number of user connections to each host in a PostgreSQL cluster.

Here are the basic principles of session pooling:

1. When creating a user, Managed Service for PostgreSQL reserves for this user 50 connections to each host in a PostgreSQL cluster by default. The minimum number of connections per user is 1.
2. The total number of connections reserved for users must not exceed the Max connections value. Managed Service for PostgreSQL reserves 15 service connections per host.

For example, if the cluster is set to "max_connections": 100, you can reserve a maximum of 85 connections per cluster host for users. At the same time, the sum of the Conn limit values for all users in the cluster must not exceed 85.

200 × <Number of vCPUs per host>

Hosts with a guaranteed vCPU share below 100% (burstable) use fixed maximum values:

• b1.nano, b1.micro, b2.nano, b2.micro: 100
• b1.medium, b2.medium: 200

By default, the maximum value is used.

You can find detailed information in this article.