doc-exports/docs/dws/dev/dws_04_0103.html

GaussDB(DWS) Connection Management Specifications

Rule 1.1: Configuring Load Balancing for GaussDB(DWS) Clusters

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.

Rule 1.2: Ending the Database Connection After Necessary Operations (Except in Connection Pool Scenarios)

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.

Rule 1.3: Ensuring a Started Transaction Is Committed or Rolled Back

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.

Rule 1.4: Ensuring the Idle Timeout Duration Is Shorter Than SESSION_TIMEOUT Value When Connection Pool Is Used for Applications

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.

Rule 1.5: Restoring Parameters to Default Values in Connections Before Returning Them to the Pool

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.

Rule 1.6: Manually Clearing Temporary Tables Created with a Connection Before Returning it to the 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.

Parent topic: GaussDB(DWS) Development Design Proposal