Warning logs are observed in MariaDB after upgrading from release 10.1 to release 10.2.

The following are seen in file mysql-error-running.log:

2021-02-26 1:46:22 47894449886976 [Warning] Aborted connection 216669 to db: 'nfvodb' user: 'master' host: 'x.x.x.x' (Got timeout reading communication packets)
2021-02-26 0:46:19 47898975540992 [Warning] Aborted connection 216242 to db: 'nfvodb' user: 'master' host: 'x.x.x.x' (Got timeout reading communication packets)
2021-02-26 0:46:22 47905486018304 [Warning] Aborted connection 216246 to db: 'nedb' user: 'master' host: 'x.x.x.x' (Got timeout reading communication packets)
2021-02-26 0:46:22 47906479949568 [Warning] Aborted connection 216244 to db: 'nfvodb' user: 'master' host: 'x.x.x.x' (Got timeout reading communication packets)

These logs may occur because of one of these reasons:

• The client connected successfully but terminated improperly (and may relate to not closing the connection properly)
• The client slept for longer than the defined wait_timeout or interactive_timeout seconds (which ends up causing the connection to sleep for wait_timeout seconds and then the connection gets forcibly closed by the MySQL server)
• The client terminated abnormally or exceeded the max_allowed_packet for queries.

Changed default value for log_warnings

Classification for level 1 and 2 log_warnings

log_warnings

• Description:  Determines which additional warnings are logged. Setting to  0  disables additional warning logging. Note that this does not prevent all warnings, there is a core set of warnings that will always be written to the error log. The additional warnings are as follows:
  • log_warnings >= 1
    • Event scheduler information.
    • System signals
    • Wrong usage of  --user
    • Failed setrlimit() and mlockall()
    • Changed limits
    • Wrong values of lower_case_table_names and stack_size
    • Wrong values for command line options
    • Start log position and some master information when starting slaves
    • Slave reconnects
    • Killed slaves
    • Error reading relay logs
    • Unsafe statements for statement-based replication. If this warning occurs frequently, it is throttled to prevent flooding the log.
    • Disabled plugins that one tried to enable or use.
    • UDF files that didn't include the required init functions.
    • DNS lookup failures.
  • log_warnings >= 2
    • Access denied errors.
    • Connections aborted or closed due to errors or timeouts.
    • Table handler errors
    • Messages related to the files used to persist replication state:
      • Either the default  master.info  file or the file that is configured by the  master_info_file  option.
      • Either the default  relay-log.info  file or the file that is configured by the  relay_log_info_file  system variable.
    • Information about a master's binary log dump thread.