Open Stack

On Mon, 2014-07-07 at 15:53 +0100, Gordon Sim wrote:
> On 07/07/2014 03:12 PM, Victor Stinner wrote:
> > The first step is to patch endpoints to add @trollius.coroutine to the methods,
> > and add yield From(...) on asynchronous tasks.
> 
> What are the 'endpoints' here? Are these internal to the oslo.messaging 
> library, or external to it?

The callback functions we dispatch to are called 'endpoint methods' -
e.g. they are methods on the 'endpoints' objects passed to
get_rpc_server().

> > Later we may modify Oslo Messaging to be able to call an RPC method
> > asynchronously, a method which would return a Trollius coroutine or task
> > directly. The problem is that Oslo Messaging currently hides "implementation"
> > details like eventlet.
> 
> I guess my question is how effectively does it hide it? If the answer to 
> the above is that this change can be contained within the oslo.messaging 
> implementation itself, then that would suggest its hidden reasonably well.
> 
> If, as I first understood (perhaps wrongly) it required changes to every 
> use of the oslo.messaging API, then it wouldn't really be hidden.
> 
> > Returning a Trollius object means that Oslo Messaging
> > will use explicitly Trollius. I'm not sure that OpenStack is ready for that
> > today.
> 
> The oslo.messaging API could evolve/expand to include explicitly 
> asynchronous methods that did not directly expose Trollius.

I'd expect us to add e.g.

  @asyncio.coroutine
  def call_async(self, ctxt, method, **kwargs):
      ...

to RPCClient. Perhaps we'd need to add an AsyncRPCClient in a separate
module and only add the method there - I don't have a good sense of it
yet.

However, the key thing is that I don't anticipate us needing to change
the current API in a backwards incompatible way.

Mark.