MySQL Manual
A Problems and Common Errors
- A.2 Common Errors When Using MySQL
- A.2.1
Access deniedError - A.2.2
MySQL server has gone awayError - A.2.3
Can't connect to [local] MySQL serverError - A.2.4
Client does not support authentication protocolerror - A.2.5
Host '...' is blockedError - A.2.6
Too many connectionsError - A.2.7
Some non-transactional changed tables couldn't be rolled backError - A.2.8
Out of memoryError - A.2.9
Packet too largeError - A.2.10 Communication Errors / Aborted Connection
- A.2.11
The table is fullError - A.2.12
Can't create/write to fileError - A.2.13
Commands out of syncError in Client - A.2.14
Ignoring userError - A.2.15
Table 'xxx' doesn't existError - A.2.16
Can't initialize character set xxxerror - A.2.17 File Not Found
- A.2.1
A.2.10 Communication Errors / Aborted Connection
Starting with MySQL 3.23.40 you only get the Aborted
connection error of you start mysqld with --warnings.
If you find errors like the following in your error log.
010301 14:38:23 Aborted connection 854 to db: 'users' user: 'josh'
See section 4.9.1 The Error Log.
This means that something of the following has happened:
-
The client program did not call
mysql_close()before exit. -
The client had been sleeping more than
wait_timeoutorinteractive_timeoutwithout doing any requests. See section 4.5.7.4SHOW VARIABLES. See section 4.5.7.4SHOW VARIABLES. - The client program ended abruptly in the middle of the transfer.
When the above happens, the server variable Aborted_clients is
incremented.
The server variable Aborted_connects is incremented when:
- When a connection packet doesn't contain the right information.
- When the user didn't have privileges to connect to a database.
- When a user uses a wrong password.
-
When it takes more than
connect_timeoutseconds to get a connect package. See section 4.5.7.4SHOW VARIABLES.
Note that the above could indicate that someone is trying to break into your database!
Other reasons for problems with Aborted clients / Aborted connections.
- Usage 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 these two machines. If a transfer goes in burst-pause-burst-pause ... mode then you are experiencing a Linux duplex syndrome. The only solution is switching duplex mode for both your network card and Hub/Switch to either full duplex or to half duplex and testing the results to decide on the best setting.
- Some problem with the thread library that causes interrupts on reads.
- Badly configured TCP/IP.
- Faulty Ethernets or hubs or switches, cables ... This can be diagnosed properly only by replacing hardware.
-
max_allowed_packetis too small or queries require more memory than you have allocated formysqld. See section A.2.9Packet too largeError.
