sqlite3 'database is locked' won't go away with retries
- by Azarias
I have a sqlite3 database that is accessed by a few threads (3-4). I am aware of the general limitations of sqlite3 with regards to concurrency as stated http://www.sqlite.org/faq.html#q6 , but I am convinced that is not the problem.
All of the threads both read and write from this database. Whenever I do a write, I have the following construct:
try:
Cursor.execute(q, params)
Connection.commit()
except sqlite3.IntegrityError:
Notify
except sqlite3.OperationalError:
print sys.exc_info()
print("DATABASE LOCKED; sleeping for 3 seconds and trying again")
time.sleep(3)
Retry
On some runs, I won't even hit this block, but when I do, it never comes out of it (keeps retrying, but I keep getting the 'database is locked' error from exc_info. If I understand the reader/writer lock usage correctly, some amount of waiting should help with the contention. What this sounds like is deadlock, but I do not use any transactions in my code, and every SELECT or INSERT is simply a one off. Some threads, however, keep the same connection when they do their operation (which includes a mix of SELECTS and INSERTS and other modifiers).
I would appericiate it if you could shade a light on this, and also ways around fixing it (besides using a different database engine.)
