[oslo][nova] Revert of oslo.messaging JSON serialization change
Balázs Gibizer
balazs.gibizer at est.tech
Mon Sep 30 15:35:53 UTC 2019
On Mon, Sep 30, 2019 at 4:45 PM, Ben Nemec <openstack at nemebean.com>
wrote:
> Hi,
>
> I've just proposed https://review.opendev.org/#/c/685724/ which
> reverts a change that recently went in to make the fake driver in
> oslo.messaging use jsonutils for message serialization instead of
> json.dumps.
>
> As explained in the commit message on the revert, this is problematic
> because the rabbit driver uses kombu's default serialization method,
> which is json.dumps. By changing the fake driver to use jsonutils
> we've made it more lenient than the most used real driver which opens
> us up to merging broken changes in consumers of oslo.messaging.
>
> We did have some discussion of whether we should try to override the
> kombu default and tell it to use jsonutils too, as a number of other
> drivers do. The concern with this was that the jsonutils handler for
> things like datetime objects is not tz-aware, which means if you send
> a datetime object over RPC and don't explicitly handle it you could
> lose important information.
>
> I'm open to being persuaded otherwise, but at the moment I'm leaning
> toward less magic happening at the RPC layer and requiring projects
> to explicitly handle types that aren't serializable by the standard
> library json module. If you have a different preference, please share
> it here.
Hi,
I might me totally wrong here and please help me understand how the
RabbitDriver works. What I did when I created the original patch that I
looked at each drivers how they handle sending messages. The
oslo_messaging._drivers.base.BaseDriver defines the interface with a
send() message. The oslo_messaging._drivers.amqpdriver.AMQPDriverBase
implements the BaseDriver interface's send() method to call _send().
Then _send() calls rpc_commom.serialize_msg which then calls
jsonutils.dumps.
The oslo_messaging._drivers.impl_rabbit.RabbitDriver driver inherits
from AMQPDriverBase and does not override send() or _send() so I think
the AMQPDriverBase ._send() is called that therefore jsonutils is used
during sending a message with RabbitDriver.
Cheers,
gibi
[1]
https://github.com/openstack/oslo.messaging/blob/7734ac1376a1a9285c8245a91cf43599358bfa9d/oslo_messaging/_drivers/amqpdriver.py#L599
>
> Thanks.
>
> -Ben
>
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