lost SQL DB connection

koahnig

I have an application writing into a table frequently. In general it does its job sufficiently and shall 24/7. In the mean time I have experienced twice a loss of connection to the DB.

When starting to write a class to safe-keep the connection details I realized QSqlDatabase may be used to retrieve the essential information and reopen.
The error message received is:

MySQL server has gone away QMYSQL: Unable to execute query

In order to prevent the problem for happening again I plan to setup up a handler. I am wondering now if a simple open to the DB shall be enough?
But on the other hand this could be already handled internally.

In the doucmentation I could find anything explaining the suituation. Did I run into a very uncommon problem?

Restarting the application again was sufficient to cure the problem. Therefore, I do not expect an external DB problem.

m.sue

Hi,
there is probably some kind of auto-disconnect by the DB after a maximum connection time or timeout after last write or read.
-Michael.

mrjj

The error message "MySQL server has gone away QMYSQL: Unable to execute query" gives many hits :) and as @m.sue suggests

http://stackoverflow.com/questions/3615422/mysql-server-has-gone-away

"By default, the server closes the connection after eight hours if nothing has happened. You can change the time limit by setting the wait_timeout variable when you start mysqld."

http://dev.mysql.com/doc/refman/5.7/en/gone-away.html

koahnig

@m-sue @mrjj thanks for your replies.

The stackoverflow link provides also the treatment. Looks a bit "wooden" ;)

mrjj

@koahnig
Well the "MySQL server has gone away" msg also seems slightly "wooden" so it fits perfectly :)