Hi all
Using asyncio, there are times when I want to execute a coroutine which is
time-consuming. I do not need the result immediately, and I do not want to
block the current task, so I want to run it in the background.
run_in_executor() can run an arbitrary function in the background, but a
coroutine needs an event loop. After some experimenting I came up with
this -
class BackgroundTask:
async def run(self, coro, args, callback=None):
loop = asyncio.get_event_loop()
loop.run_in_executor(None, self.task_runner, coro, args, callback)
def task_runner(self, coro, args, callback):
loop = asyncio.new_event_loop()
asyncio.set_event_loop(loop)
fut = asyncio.ensure_future(coro(*args))
if callback is not None:
fut.add_done_callback(callback)
loop.run_until_complete(fut)
loop.close()
Usage -
bg_task = BackgroundTask()
args = (arg1, arg2 ...)
callback = my_callback_function
await bg_task.run(coro, args, callback)
Although it 'awaits' bk_task.run(), it returns immediately, as it is simply
waiting for run_in_executor() to be launched.
Hope this is of some interest.
Frank Millman
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