If I use async workers workers with Gunicorn does my app been to be thread safe?
If you use threads, you must write your application to behave well, e.g. by always using locks to coordinate access to shared resources.
If you use events (e.g. gevent), then you generally don't need to worry about accessing shared resources, because your application is effectively single-threaded.
To answer your second question: if you use a pure python library to access your database, then gevent's monkey patching should successfully render that library nonblocking, which is what you want. But if you use a C library wrapped in Python, then monkey patching is of no use and your application will block when accessing the database.
I am correct in understand that if I use the default worker type (sync) then if the app blocks for any reason, say while waiting fo the result of a database query, the aaociated worker process will not be able to handle any further requests during this time?
I am looking for a model which doesn't require too much special coding in my app code. I understand there are two async worker types, gevent and gthread, which can solve this problem. What is the difference between these two and and does my app need to be thread safe to use these?
UPDATE - I did some reading on gevent it seems it works by monkey patching std library functions so I would think that in the case of a database query in general it probably wouldn't patch whatever db library I am using so if I would need to program my app to cooperatively yield control when I waiting on the database. Is this correct?