Sep 19, 2018

If a MySQL client successfully connects but later disconnects improperly or is terminated, the server increments the Aborted_clients status variable, and logs an Aborted connection message to the error log.

 The cause can be any of the following:

    The client program did not call mysql_close() before exiting.

    The client had been sleeping more than wait_timeout or interactive_timeout seconds without issuing any requests to the server. See Section 5.1.5, “Server System Variables”.

    The client program ended abruptly in the middle of a data transfer.

Other reasons for problems with aborted connections or aborted clients:

    The max_allowed_packet variable value is too small or queries require more memory than you have allocated for mysqld.

    Use of Ethernet protocol with Linux, both half and full duplex. Some Linux Ethernet drivers have this bug. You should test for this bug by transferring a huge file using FTP between the client and server machines. If a transfer goes in burst-pause-burst-pause mode, you are experiencing a Linux duplex syndrome. Switch the duplex mode for both your network card and hub/switch to either full duplex or to half duplex and test the results to determine the best setting.

    A problem with the thread library that causes interrupts on reads.

    Badly configured TCP/IP.

    Faulty Ethernets, hubs, switches, cables, and so forth. This can be diagnosed properly only by replacing hardware.