Rajeev Kannav Sharma

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Mysql2 Error Lost connection to MySQL server during query Rails Application

26 Sep 2015

In our Rails Application we faced several exception(s) saying

Mysql2::Error: Lost connection to MySQL server during query

Usually it indicates network connectivity trouble and you should check the condition of your network if this error occurs frequently. If the error message includes “during query,” this is probably the case you are experiencing.

Sometimes the during query form happens when millions of rows are being sent as part of one or more queries. If you know that this is happening, you should try increasing net_read_timeout from its default of 30 seconds to 60 seconds or longer, sufficient for the data transfer to complete.

In our case luckily we’re on Amazon Relational Database Machine(s), so it can be done easily and Quickly.

Visit Parameter Groups of your Amazon RDS machine. update net_read_timeout value of that group which is being used. we make it 3600. default unit in mysql is seconds

Re-booted the rds instance, though it was a down for a while. After that a new sun arise we’ve not face such exceptions yet. still we’re investigating.

And if you get stuck… Ask Here

email me rajeevsharma86@gmail.com

Tweet to me at @rajeevkannav.