Open Stack

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
>