On 10/02/2012 06:09 PM, E S wrote: > I have a service running that occasionally connects to a MySQL > database. When there is no activity on it for some time, I eventually > get the the error > > _mysql_exceptions.OperationalError: (2006, 'MySQL server has gone away') > > I have found a few posts on this group related to this issue > > http://twistedmatrix.com/pipermail/twisted-python/2007-July/015788.html > http://twistedmatrix.com/pipermail/twisted-python/2007-October/016178.html > > as well as some tickets on the twisted homepage: > > http://twistedmatrix.com/trac/ticket/4404 > http://twistedmatrix.com/trac/ticket/4964 > > I have also seen this referenced as a potential fix: > > http://www.gelens.org/2009/09/13/twisted-connectionpool-revisited/ > > I currently have the cp_reconnect parameter set to True, but it does > not appear to be doing the job. I don't really see much consensus on > how to properly handle this issue. Some people seem to think that the > cp_reconnect parameter should take care of it for you, other people > say that cp_reconnect is only part of the solution and that you have > to write your own error handling.
For what it's worth - I think adbapi is seriously sub-optimal in this regard. We have continual low-level problems with Twisted apps getting stuck due to hung/dead ConnectionPool. And if you forget cp_reconnect, well you are basically committing suicide. Your Twisted app will need a restart. In particular - it's not clear to my why CP isn't using "cp_good_sql" to probe a connection *before* starting the transaction, and to close/re-open it transparently if it has died and cp_reconnect==1. Instead, the only place the "good" SQL is run is *after* a rollback, so the next N transactions into the pool (where N is the number of threads) all fail, because they don't get as far as "rollback". I think the behaviour it should be aiming for is clear: 1. Test each connection with "good_sql" before beginning the user interaction/query 2. If execeptions occur inside the user interaction, either at cursor methods like execute, or connection methods like commit, then: 1. rollback - if *this* raises an exception, throw the conn away 2. propagate the original exception upwards unchanged (maybe wrapped, maybe not) cp_reconnect should be the default. _______________________________________________ Twisted-Python mailing list Twisted-Python@twistedmatrix.com http://twistedmatrix.com/cgi-bin/mailman/listinfo/twisted-python