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MySQL server has gone away
Error
This section also covers the related Lost connection to server
during query
error.
The most common reason for the MySQL server has gone away
error
is that the server timed out and closed the connection. By default, the
server closes the connection after 8 hours if nothing has happened. You
can change the time limit by setting the wait_timeout
variable when
you start mysqld
.
Another common reason to receive the MySQL server has gone away
error
is because you have issued a "close" on your MySQL connection
and then tried to run a query on the closed connection.
If you have a script, you just have to issue the query again for the client to do an automatic reconnection.
You normally can get the following error codes in this case (which one you get is OS-dependent):
Error code | Description |
CR_SERVER_GONE_ERROR | The client couldn't send a question to the | server.
CR_SERVER_LOST | The client didn't get an error when writing | to the server, but it didn't get a full answer (or any answer) to the question.
You will also get this error if someone has kills the running thread with
kill #threadid#
.
You can check that the MySQL hasn't died by executing mysqladmin
version
and examining the uptime. If the problem is that mysqld
crashed you should concentrate one finding the reason for the crash.
You should in this case start by checking if issuing the query again
will kill MySQL again. See section A.4.1 What To Do If MySQL Keeps Crashing.
You can also get these errors if you send a query to the server that is
incorrect or too large. If mysqld
gets a packet that is too large
or out of order, it assumes that something has gone wrong with the client and
closes the connection. If you need big queries (for example, if you are
working with big BLOB
columns), you can increase the query limit by
starting mysqld
with the -O max_allowed_packet=#
option
(default 1M). The extra memory is allocated on demand, so mysqld
will
allocate more memory only when you issue a big query or when mysqld
must
return a big result row!
You will also get a lost connection if you are sending a packet >= 16M if your client is older than 4.0.8 and your server is 4.0.8 and above, or the other way around.
If you want to make a bug report regarding this problem, be sure that you include the following information:
hostname.err file
. See section A.4.1 What To Do If MySQL Keeps Crashing.
mysqld
and the involved tables where
checked with CHECK TABLE
before you did the query, can you do
a test case for this? See section D.1.6 Making a Test Case If You Experience Table Corruption.
wait_timeout
variable in the MySQL server ?
mysqladmin variables
gives you the value of this
mysqld
with --log
and check if the
issued query appears in the log ?
See section 1.7.1.2 Asking Questions or Reporting Bugs.
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