(mysql.info.gz) Communication errors

 
 A.2.10 Communication Errors and Aborted Connections
 ---------------------------------------------------
 
 The server error log can be a useful source of information about
 connection problems.   Error log.  Starting with MySQL 3.23.40,
 if you start the server with the `--warnings' option (or
 `--log-warnings' from MySQL 4.0.3 on), 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.   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.   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'.  
      Packet too large.
 
 See also  Gone away.
Info Catalog
(mysql.info.gz) Packet too large
(mysql.info.gz) Common errors
(mysql.info.gz) Full table
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