使用异步关闭 Python 中的连接

Question

I am trying to retrieve data from a database for use in an api context. However I noticed that conn.close() was taking a relatively long time to execute (in this context conn is a connection from a mysql connection pool). Since closing the connection is not blocking the api's ability to return data I figured I would use asyncio to close the connection async so it wouldn't block the data being returned.

async def get_data(stuff):
    conn = api.db.get_connection()
    cursor = conn.cursor(dictionary=True)
    data = execute_query(stuff, conn, cursor)
    cursor.close()
    asyncio.ensure_future(close_conn(conn))
    return helper_rows

async def close_conn(conn):
    conn.close()

results = asyncio.run(get_data(stuff))

However despite the fact the asyncio.ensure_future(close(conn)) is not blocking (I put timing statements in to see how long everything was taking and the ones before and after this command were about 1ms different) the actual result won't be gotten until close_conn is completed. (I verified this using time statements and the difference in time between when it reaches the return statement in get_data and when the line after results=asyncio.run(get_data(stuff)) is about 200ms).

So my question is how do I make this code close the connection in the background so I am free to go ahead and process the data without having to wait for it.

Answer 1

Since conn.close() is not a coroutine it blocks the event loop when close_conn is scheduled. If you want to do what you described, use an async sql client and do await conn.close() .

Answer 2

You could try using an asynchronous context manager. (async with statement)

async def get_data(stuff):
    async with api.db.get_connection() as conn:
        cursor = conn.cursor(dictionary=True)
        data = execute_query(stuff, conn, cursor)
        cursor.close()
        asyncio.ensure_future(close_conn(conn))
        return helper_rows

results = asyncio.run(get_data(stuff))

If that doesn't work the sql client you are using try with aiosqlite.

https://github.com/omnilib/aiosqlite

import aiosqlite