Question

Say I have a Flask application, served by uWSGI using multiple processes, like:

uwsgi --socket 127.0.0.1:3031 --file flaskapp.py --callable app --processes 4

And my Flask app is organized like this:

/flaskapp
    app.py
    /db
        __init__.py
        somefile.py
        somefile2.py
        ...

And I’m using boto to connect to DynamoDB. The __init__.py file is empty, and each somefilexxx.py file begins something like this:

db = boto.connect_dynamodb()
table = db.get_table('table')
def do_stuff_with_table():

I don’t use threads in the app, and I don’t think uWSGI uses threads unless I explicitly enable them with --threads. Does this setup make sense? Are there any threading issues I have to worry about with urllib (you might guess I know less than nothing about threads…)?

Alternatively, would it make more sense to call connect_dynamodb() in the __init__.py file and only load the tables in the somefile.py files?

Answer 1

Since you haven’t enabled threads in uWSGI (see: --enable-threads, --threads) there’s no Python threading going on here (in Boto or otherwise.)

I would recommend using --lazy, which will cause your app to be loaded in each worker post-fork. Then you can simply rely on that behavior to ensure each worker has the appropriate connections/pools/etc. available without the concerns of shared state.