Mysql2::Error: This connection is still waiting for a result, try again once you have the result

[Jason Fleetwood-Boldt]

Rails-talk, 

Last night I got a slew (around 2000) of these exceptions raised in my production app between 4:03 AM and 7:30 AM (eastern time). 

They all had the same pattern:

ActiveRecord::StatementInvalid: Mysql2::Error: This connection is still waiting for a result, try again once you have the result: SELECT `spree_buckets`.* FROM `spree_buckets` WHERE `spree_buckets`.`slug` = 'gallery' LIMIT 1

(The SQL query was different for many, but the Mysql2::Error: This connection is still waiting for a result, try again once you have the result part was the same)

I called Amazon RDS support and they said the underlying database looked fine, we are well below our IOPS threshold, and our queue depth looks healthy.

I think perhaps just 1 Unicorn worker choked up with a single MySQL call, resulting in all subsequent calls from that Unicorn worker to produce this error (for 3 hours!)

Does anyone else have any best practice advice for this error? Should I simply catch for this exception and close & reconnect any active MySQL connections ? Can someone share some examples of how to do that as cleanly as possible?

Thanks,

Jason

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Jason Fleetwood-Boldt

te...@datatravels.com

http://www.jasonfleetwoodboldt.com/writing

[Kevin Disneur]

We encountered this exactly same problem this night. We've also called AWS and they gave us the same answer: everything looks fine on your instance.

We have several applications using this same database, they all worked fined except one. So It really looks like a problem in either mysql2 or unicorn.

Did you manage to find an explanation? And maybe a solution? For the moment we have just restarted the application and everything is back to normal.

Thanks,

Kevin