python - How to lock a critical section in Django?

Question

I can't find a good clean way to lock a critical section in Django. I could use a lock or semaphore but the python implementation is for threads only, so if the production server forks then those will not be respected. Does anyone know of a way (I am thinking posix semaphores right now) to guarantee a lock across processes, or barring that a way to stop a Django server from forking.

Answer 1

If you use RDBMS, you can use its "LOCK" mechanism. For example, while one "SELECT FOR UPDATE" transaction locks a row, the other "SELECT FOR UPDATE" transactions with the row must wait.

# You can use any Python DB API.
[SQL] BEGIN;

[SQL] SELECT col_name FROM table_name where id = 1 FOR UPDATE;

[Process some python code]

[SQL] COMMIT;