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auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=stefanha@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="HkZ3/K4zZulci4ZO" Content-Disposition: inline Received-SPF: pass client-ip=170.10.133.124; envelope-from=stefanha@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: armbru@redhat.com, crosa@redhat.com, qemu-devel@nongnu.org, ehabkost@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" --HkZ3/K4zZulci4ZO Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Apr 14, 2021 at 01:50:37PM -0400, John Snow wrote: > On 4/14/21 1:44 AM, Stefan Hajnoczi wrote: > > 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 a= void > > > + 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 fai= l > > > + 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 =3D cast(str, msg['id']) > > > + self.logger.debug("Execute(%s): '%s'", exec_id, > > > + msg.get('execute', msg.get('exec-oob'))) > > > + > > > + queue: asyncio.Queue[Message] =3D asyncio.Queue(maxsize=3D1) > > > + task =3D create_task(self._bh_execute(msg, queue)) > >=20 > > We're already in a coroutine, can we await queue.get() ourselves instea= d > > of creating a new task? > >=20 > > 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. > >=20 >=20 > ...queues do not have a cancellation signal :( :( :( :( >=20 > There's no way to "cancel" a queue: > https://docs.python.org/3/library/asyncio-queue.html#queue >=20 > You *could* craft a special message and inject an exception into the queu= e > to notify the reader that the message will never arrive, but it feels lik= e > working against the intended mechanism of that primitive. It really feels > like it wants to be wrapped in a *task*. That's what I meant by "it seems simpler to use the queue both for success and cancellation". Just queue a message that says the execution has been cancelled. Stefan --HkZ3/K4zZulci4ZO Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEhpWov9P5fNqsNXdanKSrs4Grc8gFAmB4BfoACgkQnKSrs4Gr c8jfyQf/Xn5etqeGKyaKORLtHItzOZli5dFFflU0YwRYMWklX/0KGi47J/fCL408 ZvES3nETr4h47s1HC3xGhUEuTItibY3IlU/+4cERSE7ynshsEv5d8mU/AgaSBcmx WmG+hMUZOJBabqma+beB7EO4qanU+Q3H+ApHtLjSNMygRakwB4mnd4cywaNEI2kA d2MGquuhHz+42rsRNyPyoW4YxDwHoIkwZJVOSRUhabjayfJbFo3crHYnBTJp1Szu NsNs0KZjbGgE3XdOGIXmZJIAhnkrkNH/JVnzmhwZ2Gy4lgR/AvLXj1tC0G3izKgV xiM6D0b+W4kHuvvPbGeOOk4CZ97i0w== =Ij13 -----END PGP SIGNATURE----- --HkZ3/K4zZulci4ZO--