Spawn threads as daemon so program will exit with main thread.

[ethan-vanderheijden]

Description

Currently, the threads spawned by aiosqlite's Connection are non-daemon threads, so if you don't explicitly close the connection, the program will stay alive after the main thread exits.

The following aiosqlite code will never exit:

import asyncio
import aiosqlite

async def create_db():
    db = await aiosqlite.connect('../database/partners_list.db')

asyncio.run(create_db())

But the equivalent sqlite code does exit:

import sqlite3

def create_db():
    db = sqlite3.connect('../database/partners_list.db')

create_db()

In my use case, I want to use aiosqlite with Quart, but because I don't want to create a database connection + thread for every request, I will do all my databasing with a single, global connection. However, I'm not sure when the web server will exit and I don't want the program to hang if the database connection hasn't been explicitly closed.

Details

• OS: Ubuntu 22
• Python version: 3.10
• aiosqlite version: 0.20.0
• Can you repro on 'main' branch? yes
• Can you repro in a clean virtualenv? yes

[amyreese]

My main concern with daemonizing the thread is that it potentially allows the database connection to silently close without finalizing transactions/writes, and may result in database corruption.

The "database thread hanging" issue feels to me like it's really a symptom of other problems, and a better solution would be to ensure that your program doesn't exit without explicitly calling close() on the connection, or by using a context manager to ensure that connections close automatically.

Specifically for Quart, I would suggest using the @app.while_serving or @app.after_serving to cleanly and safely close your connections on exit rather than daemonizing threads with shared sqlite connections.