GaussDB(DWS) Connection Management Specifications

Impact of rule violation:

• Load imbalance causes performance problems and even service interruption.
• When a CN is faulty, services cannot be automatically recovered or the recovery may take a long time.

Solution:

• Configure ELB load balancing and connect the application to the load balancing IP address.
• For how to use the JDBC for load balancing, see Configuring JDBC to Connect to a Cluster (Load Balancing Mode).

Impact of rule violation:

• The number of idle connections exceeds the maximum limit, causing connection creation failure.
• Resource overload occurs because there are too many idle connections.

Solution:

• After the connection between the application and the database is established and used, manually end the connection.
• Set the session_timeout parameter on the service side to set the idle timeout duration. The connection will be automatically ended when the idle timeout duration expires.

Impact of rule violation:

• If a transaction remains uncommitted for an extended period, it blocks operations such as ALTER, thereby affecting all services.
• The number of idle connections exceeds the maximum limit, causing connection creation failure.

Solution:

• autocommit is enabled by default, so there is no need to manually commit any transaction unless you modify the default setting.
• If a transaction is explicitly started, it must be explicitly ended (either by committing or rolling back) once the relevant operations are finished.

Impact of rule violation:

• The idle timeout mechanism on the service side clears connections in the connection pool, which negatively impacts connection reuse.

Solution:

• To ensure everything works correctly, make sure the idle timeout duration of the connection pool is shorter than the SESSION_TIMEOUT value in GaussDB(DWS). It is advised to adjust the idle timeout duration rather than modifying the SESSION_TIMEOUT value.

Impact of rule violation:

• When a connection is reused by another service, the parameters set by the service may also be reused. This can result in performance issues or service errors.

Solution:

• Before returning the connection to the connection pool, use SET SESSION AUTHORIZATION DEFAULT;RESET ALL; to reset parameters.

Notes:

When connection pool is used for applications, if you set the global GUC parameter using GS_GUC RELOAD in GaussDB(DWS), restart the connection pool for the changes to be applied. This is because the modification only affects new connections in the connection pool.

Impact of rule violation:

• When a connection is reused by other services, an error may be reported when a temporary table is created.

Solution:

• Before returning a connection to the connection pool, use DROP to clear the temporary table created by the current session.