How do I resolve the "Got an error reading communication packets" error in Amazon RDS for MySQL or Aurora MySQL-Compatible?

Short description

If server-client connections are dropped, improperly closed, or are unsuccessful, then Amazon RDS increments the status counter for either aborted_clients or aborted_connects. The aborted_clients parameter describes the number of connections that were aborted because the client died without closing the connection properly. The aborted_connects parameter describes the number of failed attempts to connect to the MySQL server.

log_error_verbosity specifies the verbosity for handling events intended for the error log. If this parameter's value exceeds a value of 2, then RDS for MySQL writes this information to your error log:

[Warning] Aborted connection xxx to db: '<database name>' user: '<user name>' host: '<host IP>' (Got an error reading communication packets)

This warning is triggered whenever the status counter for the aborted_clients or aborted_connects metric values are incremented. Amazon RDS uses the database error logs to retrieve this information. For more information, see Communication errors and aborted connections on the MySQL server website.

Factors that can trigger the Aborted connection warning include but aren't limited to:

• Client or driver incompatibility
• Firewalls or proxies, which can close any idle connections or block a connection.
• Improper closing of a client-server connection, resulting in a higher number of sleeping connections inside RDS for MySQL.
• A client application that improperly terminates a connection. If connections are left idle for a certain amount of time then MySQL forcibly closes these connections. You then see the Aborted connection message.
• Idle connections that exceed the wait_timeout or interactive_timeout thresholds.
• A client connection that exceeds the connect_timeout seconds threshold when obtaining a connection packet.
• Insufficient values for parameters like net_write_timeout and net_read_timeout.
• The max_allowed_packet parameter value is exceeded. If the value is too small or queries require more memory than is allocated for RDS for MySQL, this triggers the Aborted connection warning.

Resolution

If you receive an Aborted connection error in RDS for MySQL or Aurora MySQL-Compatible, be sure to review your MySQL parameter values. After you identify the root cause of your issue, update the parameter and test the new value, while monitoring the MySQL error logs.

As you troubleshoot the Aborted Connection error in Amazon RDS, consider these approaches:

• Check to see if you're using the default values of an Amazon RDS parameter group. The default values for parameters related to connectivity timeouts might not be appropriate for your DB instance. For more information, see the Parameters related to connectivity timeout section of Best practices for configuring parameters for Amazon RDS for MySQL.
• Set a higher value for connect_timeout to see if this helps to reduce the occurrence of the Aborted connection error messages. This parameter specifies how long the MySQL server instance must wait (in seconds) before responding with a bad handshake.
• Modify interactive_timeout and wait_timeout. Applications that use connection pooling (like Java) must have timeouts that match the connection pool settings.
• Increase the value of max_allowed_packet if the instance must handle big queries. If a row has more data than the max_allowed_packet value for the client, then errors are reported. Increase this value if you are using large BLOB columns or long strings. For more information, see the max_allowed_packet section of Best practices for configuring parameters for Amazon RDS for MySQL.
• Increase the net_write_timeout and net_read_timeout values. Note: These values can be set to the same value as wait_timeout.
• Make sure that the RDS for MySQL or Aurora MySQL-Compatible connections are properly closed. Before exiting the database, make sure to call the mysql_close() function from the client application.

Troubleshooting tips

If you're still receiving the Aborted connection error message, try the following troubleshooting tips:

• Turn on Performance Insights to retrieve the timeframe of the SQL statements that are causing the warning. For Aurora MySQL-Compatible, see Monitoring DB load with Performance Insights on Amazon Aurora.
• Turn on slow query logging on your Amazon RDS or Aurora MySQL DB instance. This captures and log any queries running for longer than long_query_time, which by default is 10 seconds. For more information, refer to How do I activate and monitor logs for an Amazon RDS for MySQL DB instance?
• Consider turning on VPC Flow Logs. VPC Flow Logs allows you to see from which side (client/server) that the connection is being closed from.
• Make sure that your application properly closed the connection from MySQL.
• Run the tcpdump command from the machine that's running the client to test sample packet captures. For example:

sudo tcpdump -vvv --interface eth0 port 3306 -W 10 -C 100

Related information

How do I modify the values of an Amazon RDS DB parameter group?

Why did DB connections drop on my RDS DB instance?

How can I turn on logs on an Aurora Serverless cluster so I can view and download the logs?