Rate limiting connections

Each connection to a YugabyteDB cluster uses CPU and memory, so it is important to consider how many connections are needed for the application. YugabyteDB uses a max_connections setting to limit the number of connections per node in the cluster (and thereby the resources that are consumed by connections) to prevent run-away connection behavior from overwhelming your deployment's resources.

You can check the value of max_connections with your admin user and ysqlsh.

SHOW max_connections;
 max_connections
-----------------
 300
(1 row)

Limiting connections per tenant

Sometimes it is important to limit the number of connections per tenant. In order to achieve this, map a tenant to a database and a user (or a service account), and rate limit the number of connections per database for the user. This can be achieved as shown in this section.

Setup database and user

First create a database, as shown below.

create database test_connection;

Next, create a user. Make sure the user you create is not a superuser. For superusers, there is no limit on the number of connections.

create role test_user login;

Limit connections per DB

Set connection limit for database as shown below.

alter database test_connection CONNECTION LIMIT 1;

You can display the limits as shown below.

select datname, datconnlimit from pg_database where datname =’test_connection’ ;

       datname     | datconnlimit
-----------------+--------------
 test_connection |            1

Test connection limit

To test, launch two connections to the database.

The first connection should succeed.

./bin/ysqlsh -U test_user test_connection
This is successful

The second connection should fail.

./bin/ysqlsh -U test_user test_connection
ysqlsh: FATAL:  too many connections for database "test_connection"