Description

Enabling the log_disconnections setting logs the end of each session, including the session duration.

Rationale

PostgreSQL does not log session details such as duration and session end by default. Enabling the log_disconnections setting will create log entries at the end of each session, which can be useful in troubleshooting issues and determining any unusual activity across a time period. The log_disconnections and log_connections settings work together and generally, the pair would be enabled or disabled together. This recommendation is applicable to PostgreSQL database instances.

Impact

Turning on logging will increase the required storage over time. Mismanaged logs may cause your storage costs to increase. 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.

Remediation

From the console

1. Go to the Cloud SQL Instances page.
2. Select the PostgreSQL instance where the database flag needs to be enabled.
3. Click Edit.
4. Scroll down to the Flags section.
5. To set a flag that has not been set on the instance before, click Add item, choose the flag log_disconnections from the drop-down menu and set the value as on.
6. Click Save.
7. Confirm the changes under Flags on the Overview page.

From the command line

1. Configure the log_disconnections database flag for every Cloud SQL PosgreSQL database instance using the below command:

   gcloud sql instances patch <INSTANCE_NAME> --database-flags
   log_disconnections=on
   

   Note: This command will overwrite all previously set database flags. To keep those and add new ones, include the values for all flags to be set on the instance; any flag not specifically included is set to its default value. For flags that do not take a value, specify the flag name followed by an equals sign ("=").

Default Value

By default, log_disconnections is off.

References

1. https://cloud.google.com/sql/docs/postgres/flags
2. https://www.postgresql.org/docs/9.6/runtime-config-logging.html#RUNTIME-CONFIG-LOGGING-WHAT

Additional Information

• Configuring the log_disconnections flag does not require restarting the Cloud SQL instance.
• Although the log_disconnections flag does not require a restart, you might modify other database flag values when you apply this patch. Many database flags require restarting the Cloud SQL instance. Before you modify a database flag, check the list of supported flags to see if your instance will be restarted when this patch is submitted.
• 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.

CIS controls

Version 8, 8.5 Collect Detailed Audit Logs

• Configure detailed audit logging for enterprise assets containing sensitive data. Include event source, date, username, timestamp, source addresses, destination addresses, and other useful elements that could assist in a forensic investigation.