I’m just learning Google App Engine and am trying to figure out a good approach to managing my database connection to a Google Cloud SQL instance (if you haven’t used GC-SQL, basically, it’s MySQL in the cloud, with a few limitations).
I’m using the python (2.7) GAE environment with the webapp2 framework for handling requests. I know the FAQ says that it’s recommended that a new connection to the DB be made with each request, but I don’t know what the recommended way of closing the connection is. Each time I try to drop tables during development, the GC-SQL hangs and "show processlist" shows that there are a bunch of processes (likely because I’m not closing the DB) and that one of them is waiting for a lock (likely the process trying to drop the tables). This is annoying and forces me to restart the GC-SQL instance (like restarting mysql-server service, I imagine). There are also occasional DB hiccups that I believe are related to the fact that I’m not really closing my DB connection.
So, for example, should I have a destructor on my webapp2.Requesthandler subclass instance to disconnect from the DB? GAE objects seem to be cached sometimes, so that’s also something to consider. I suppose I could just connect/query/disconnect for each query, but this seems suboptimal.
I know this is a vague question, but I’m hoping someone who’s played in this area can thow some tips my way.
Thanks in advance!
Update:
I tried implementing a wrapper around methods that need a cursor, using Shay’s answer as a starting point. I’m getting GAE errors. Here’s a new question specific to that: What are the connection limits for Google Cloud SQL from App Engine, and how to best reuse DB connections?
I’m not familiar with Google Cloud SQL, but couldn’t you use a WSGI middleware to open and close the connection?