使用 async emit 创建一个 logging.Handler

Question

I have a Python log handler that writes using asyncio (it's too much work to write to this particular service any other way). I also want to be able to log messages from background threads, since a few bits of code do that. So my code looks basically like this (minimal version):

class AsyncEmitLogHandler(logging.Handler):
    def __init__(self):
        self.loop = asyncio.get_running_loop()
        super().__init__()

    def emit(self, record):
        self.format(record)
        asyncio.run_coroutine_threadsafe(
            coro=self._async_emit(record.message),
            loop=self.loop,
        )

    async def _async_emit(message):
        await my_async_write_function(message)

Mostly it works fine but when processes exit I get a lot some warnings like this: "coroutine 'AsyncEmitLogHandler._async_emit' was never awaited"

Any suggestions on a cleaner way to do this? Or some way to catch shutdown and kill pending writes? Or just suppress the warnings?

Note: the full code is [here][1] [1]: https://github.com/lsst-ts/ts_salobj/blob/c0c6473f7ff7c71bd3c84e8e95b4ad7c28e67721/python/lsst/ts/salobj/sal_log_handler.py

Answer 1

You could keep a reference to the coro, and override the handler's close() method to call close() on it. A general way to manage coros is to keep a list of them in the handler, and override the handler's close() method to call close() on each coro, or else create tasks from them and call cancel() on each of the tasks.