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Description

It is recommended to check the user connections for a Cloud SQL SQL Server instance to ensure that it is not artificially limiting connections.

Rationale​

The user connections option specifies the maximum number of simultaneous user connections that are allowed on an instance of SQL Server. The actual number of user connections allowed also depends on the version of SQL Server that you are using, and also the limits of your application or applications and hardware. SQL Server allows a maximum of 32,767 user connections. Because user connections is by default a self-configuring value, with SQL Server adjusting the maximum number of user connections automatically as needed, up to the maximum value allowable. For example, if only 10 users are logged in, 10 user connection objects are allocated. In most cases, you do not have to change the value for this option. The default is 0, which means that the maximum (32,767) user connections are allowed. However if there is a number defined here that limits connections, SQL Server will not allow anymore above this limit. If the connections are at the limit, any new requests will be dropped, potentially causing lost data or outages for those using the database.

Impact​

Setting custom flags via command line on certain instances will cause all omitted flags to be reset to defaults. This may cause you to lose custom flags and could result in unforeseen complications or instance restarts. Because of this, it is recommended you apply these flags changes during a period of low usage.

Audit​

From Google Cloud Console​

  1. Go to the Cloud SQL Instances page in the Google Cloud Console by visiting https://console.cloud.google.com/sql/instances.
  2. Select the instance to open its Instance Overview page
  3. Ensure the database flag user connections listed under the Database flags section is 0.

From Google Cloud CLI​

  1. Ensure the below command returns a value of 0, for every Cloud SQL SQL Server database instance.

         gcloud sql instances describe <INSTANCE_NAME> --format=json | jq '.settings.databaseFlags[] | select(.name=="user connections")|.value'

Default Value​

By default user connections is set to '0' which does not limit the number of connections, giving the server free reign to facilitate a max of 32,767 connections.

References​

  1. https://cloud.google.com/sql/docs/sqlserver/flags
  2. https://docs.microsoft.com/en-us/sql/database-engine/configure-windows/configure-the-user-connections-server-configuration-option?view=sql-server-ver15
  3. https://www.stigviewer.com/stig/ms_sql_server_2016_instance/2018-03-09/finding/V-79119

Additional Information​

WARNING: This patch modifies database flag values, which may require your instance to be restarted. Check the list of supported flags - https://cloud.google.com/sql/docs/sqlserver/flags - to see if your instance will be restarted when this patch is submitted.

Note: some database flag settings can affect instance availability or stability, and remove the instance from the Cloud SQL SLA. For information about these flags, see Operational Guidelines.

Note: Configuring the above flag does not restart the Cloud SQL instance.