A.2.10. Communication Errors and Aborted Connections
The server error log can be a useful source of information about
connection problems. See Section 5.11.2, “The Error Log”. If you
start the server with the --log-warnings
option, you might find messages like this in your error log:
010301 14:38:23 Aborted connection 854 to db: 'users' user: 'josh'
If Aborted connections messages appear in 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 5.2.2, “Server System Variables”.
The client program ended abruptly in the middle of a data
transfer.
When any of these things happen, the server increments the
Aborted_clients status variable.
The server increments the Aborted_connects
status variable when the following things happen:
A client doesn't have privileges to connect to a database.
A client uses an incorrect password.
A connection packet doesn't contain the right information.
It takes more than connect_timeout
seconds to get a connect packet. See
Section 5.2.2, “Server System Variables”.
If these kinds of things happen, it might indicate that someone
is trying to break into your server!
Other reasons for problems with aborted clients or aborted
connections:
Use of Ethernet protocol with Linux, both half and full
duplex. Many Linux Ethernet drivers have this bug. You
should test for this bug by transferring a huge file via FTP
between the client and server machines. If a transfer goes
in burst-pause-burst-pause mode, you are experiencing a
Linux duplex syndrome. The only solution is switching the
duplex mode for both your network card and hub/switch to
either full duplex or to half duplex and testing the results
to determine the best setting.
Some 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.
The max_allowed_packet variable value is
too small or queries require more memory than you have
allocated for mysqld. See
Section A.2.9, “Packet too large”.
See also Section A.2.8, “MySQL server has gone away”.
