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From: Hanna Reitz <hreitz@redhat.com>
To: John Snow <jsnow@redhat.com>, qemu-devel@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>,
	Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>,
	Eduardo Habkost <ehabkost@redhat.com>,
	qemu-block@nongnu.org, Cleber Rosa <crosa@redhat.com>
Subject: Re: [PATCH 04/15] python/qmp: clear events on get_events() call
Date: Fri, 17 Sep 2021 14:51:30 +0200	[thread overview]
Message-ID: <bc3f4366-6fa9-750d-3e33-ac8c3deaad2b@redhat.com> (raw)
In-Reply-To: <20210917054047.2042843-5-jsnow@redhat.com>

On 17.09.21 07:40, John Snow wrote:
> All callers in the tree *already* clear the events after a call to
> get_events(). Do it automatically instead and update callsites to remove
> the manual clear call.
>
> These semantics are quite a bit easier to emulate with async QMP, and
> nobody appears to be abusing some emergent properties of what happens if
> you decide not to clear them, so let's dial down to the dumber, simpler
> thing.
>
> Specifically: callers of clear() right after a call to get_events() are
> more likely expressing their desire to not see any events they just
> retrieved, whereas callers of clear_events() not in relation to a recent
> call to pull_event/get_events are likely expressing their desire to
> simply drop *all* pending events straight onto the floor. In the sync
> world, this is safe enough; in the async world it's nearly impossible to
> promise that nothing happens between getting and clearing the
> events.
>
> Making the retrieval also clear the queue is vastly simpler.
>
> Signed-off-by: John Snow <jsnow@redhat.com>
> ---
>   python/qemu/machine/machine.py | 1 -
>   python/qemu/qmp/__init__.py    | 4 +++-
>   python/qemu/qmp/qmp_shell.py   | 1 -
>   3 files changed, 3 insertions(+), 3 deletions(-)

[...]

> diff --git a/python/qemu/qmp/__init__.py b/python/qemu/qmp/__init__.py
> index 269516a79b..ba15668c25 100644
> --- a/python/qemu/qmp/__init__.py
> +++ b/python/qemu/qmp/__init__.py
> @@ -374,7 +374,9 @@ def get_events(self, wait: bool = False) -> List[QMPMessage]:
>           @return The list of available QMP events.
>           """
>           self.__get_events(wait)
> -        return self.__events
> +        events = self.__events
> +        self.__events = []
> +        return events

Maybe it’s worth updating the doc string that right now just says “Get a 
list of available QMP events”?

(Also, perhaps renaming it to get_new_events, but that’s an even weaker 
suggestion.)

Anyway:

Reviewed-by: Hanna Reitz <hreitz@redhat.com>



  reply	other threads:[~2021-09-17 12:52 UTC|newest]

Thread overview: 51+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-17  5:40 [PATCH 00/15] Switch iotests to using Async QMP John Snow
2021-09-17  5:40 ` [PATCH 01/15] python/aqmp: add greeting property to QMPClient John Snow
2021-09-17 12:20   ` Hanna Reitz
2021-09-17  5:40 ` [PATCH 02/15] python/aqmp: add .empty() method to EventListener John Snow
2021-09-17 12:25   ` Hanna Reitz
2021-09-17  5:40 ` [PATCH 03/15] python/aqmp: Return cleared events from EventListener.clear() John Snow
2021-09-17 12:36   ` Hanna Reitz
2021-09-17 17:19     ` John Snow
2021-10-04  9:03       ` Hanna Reitz
2021-09-17  5:40 ` [PATCH 04/15] python/qmp: clear events on get_events() call John Snow
2021-09-17 12:51   ` Hanna Reitz [this message]
2021-09-17 17:31     ` John Snow
2021-09-17  5:40 ` [PATCH 05/15] python/qmp: add send_fd_scm directly to QEMUMonitorProtocol John Snow
2021-09-17 13:21   ` Hanna Reitz
2021-09-17 17:36     ` John Snow
2021-09-17  5:40 ` [PATCH 06/15] python, iotests: remove socket_scm_helper John Snow
2021-09-17 13:24   ` Hanna Reitz
2021-09-17  5:40 ` [PATCH 07/15] python/aqmp: add send_fd_scm John Snow
2021-09-17 13:34   ` Hanna Reitz
2021-09-17 18:05     ` John Snow
2021-09-17  5:40 ` [PATCH 08/15] python/aqmp: Create MessageModel and StandaloneModel classes John Snow
2021-09-17 13:39   ` Hanna Reitz
2021-09-17 19:21     ` John Snow
2021-09-17  5:40 ` [PATCH 09/15] python/machine: remove has_quit argument John Snow
2021-09-17 13:59   ` Hanna Reitz
2021-09-17 23:12     ` John Snow
2021-09-17  5:40 ` [PATCH 10/15] python/machine: Add support for AQMP backend John Snow
2021-09-17 14:16   ` Hanna Reitz
2021-09-17 23:48     ` John Snow
2021-10-04  9:43       ` Hanna Reitz
2021-09-17  5:40 ` [PATCH 11/15] python/aqmp: Create sync QMP wrapper for iotests John Snow
2021-09-17 14:23   ` Hanna Reitz
2021-09-18  0:01     ` John Snow
2021-09-17  5:40 ` [PATCH 12/15] iotests: Disable AQMP logging under non-debug modes John Snow
2021-09-17 14:30   ` Hanna Reitz
2021-09-18  0:58     ` John Snow
2021-09-18  2:14       ` John Snow
2021-10-04 10:12         ` Hanna Reitz
2021-10-04 18:32           ` John Snow
2021-10-04 21:26             ` John Snow
2021-10-05 15:12             ` Hanna Reitz
2021-10-04  9:52       ` Hanna Reitz
2021-09-17  5:40 ` [PATCH 13/15] iotests: Accommodate async QMP Exception classes John Snow
2021-09-17 14:35   ` Hanna Reitz
2021-09-18  1:12     ` John Snow
2021-09-17  5:40 ` [PATCH 14/15] python/aqmp: Remove scary message John Snow
2021-09-17 14:38   ` Hanna Reitz
2021-09-17 15:15     ` John Snow
2021-09-17  5:40 ` [PATCH 15/15] python, iotests: replace qmp with aqmp John Snow
2021-09-17 14:40   ` Hanna Reitz
2021-09-17 14:55     ` John Snow

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