Re: [PATCH RFC 6/7] qmp_protocol: add QMP client implementation

[Stefan Hajnoczi]

On Tue, Apr 13, 2021 at 11:55:52AM -0400, John Snow wrote:
> +    async def _execute(self, msg: Message) -> object:
> +        """
> +        The same as `execute_msg()`, but without safety mechanisms.
> +
> +        Does not assign an execution ID and does not check that the form
> +        of the message being sent is valid.
> +
> +        This method *Requires* an 'id' parameter to be set on the
> +        message, it will not set one for you like `execute()` or
> +        `execute_msg()`.
> +
> +        Do not use "__aqmp#00000" style IDs, use something else to avoid
> +        potential clashes. If this ID clashes with an ID presently
> +        in-use or otherwise clashes with the auto-generated IDs, the
> +        response routing mechanisms in _on_message may very well fail
> +        loudly enough to cause the entire loop to crash.
> +
> +        The ID should be a str; or at least something JSON
> +        serializable. It *must* be hashable.
> +        """
> +        exec_id = cast(str, msg['id'])
> +        self.logger.debug("Execute(%s): '%s'", exec_id,
> +                          msg.get('execute', msg.get('exec-oob')))
> +
> +        queue: asyncio.Queue[Message] = asyncio.Queue(maxsize=1)
> +        task = create_task(self._bh_execute(msg, queue))

We're already in a coroutine, can we await queue.get() ourselves instead
of creating a new task?

I guess this is done in order to use Task.cancel() in _bh_disconnect()
but it seems simpler to use queue both for success and cancellation.
Fewer tasks are easier to reason about.

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