import asyncio
import motor.motor_asyncio
import multiprocessing
import pymongo.cursor

async def main():
    jobs = multiprocessing.cpu_count() * 5
    client = motor.motor_asyncio.AsyncIOMotorClient()

    async def job():
        async for it in client.local.oplog.rs.find(
            {'stall': True},
            cursor_type=pymongo.cursor.CursorType.TAILABLE_AWAIT,
        ):
            print('got', it) # never reached (as expected)

    [asyncio.create_task(job()) for _ in range(jobs)]
    await asyncio.sleep(1)

    # now the complete motor thread pool is filled with blocking jobs that are waiting for a new document 
   # and this will stall indefinitely
    print('inserting')
    await client.db.col.insert_one({})
    print('ok') # never reached

asyncio.run(main())