loop.py 文件源码

def start_task(self, task: Task) -> None:
        '''Initialize the task, queue it for execution, add the done callback,
        and keep track of it for when tasks need to be stopped.'''

        try:
            Log.debug('task %s starting', task.name)
            before = time.time()
            task.counters['last_run'] = before

            task.running = True
            self.running_tasks.add(task)
            await task.run_task()
            Log.debug('task %s completed', task.name)

        except CancelledError:
            Log.debug('task %s cancelled', task.name)

        except Exception:
            Log.exception('unhandled exception in task %s', task.name)

        finally:
            self.running_tasks.discard(task)
            task.running = False
            task.task = None

            after = time.time()
            total = after - before
            task.counters['last_completed'] = after
            task.counters['duration'] = total