Hi Andrew, Sorry for this late response, I missed it.
2015-06-25 23:22 GMT+09:00 Andrew Laski <and...@lascii.com>: > I have been growing concerned recently with some attempts to formalize > scheduler hints, both with API validation and Nova objects defining them, > and want to air those concerns and see if others agree or can help me see > why I shouldn't worry. > > Starting with the API I think the strict input validation that's being done, > as seen in > http://git.openstack.org/cgit/openstack/nova/tree/nova/api/openstack/compute/schemas/v3/scheduler_hints.py?id=53677ebba6c86bd02ae80867028ed5f21b1299da, > is unnecessary, and potentially problematic. > > One problem is that it doesn't indicate anything useful for a client. The > schema indicates that there are hints available but can make no claim about > whether or not they're actually enabled. So while a microversion bump would > typically indicate a new feature available to an end user, in the case of a > new scheduler hint a microversion bump really indicates nothing at all. It > does ensure that if a scheduler hint is used that it's spelled properly and > the data type passed is correct, but that's primarily useful because there > is no feedback mechanism to indicate an invalid or unused scheduler hint. I > think the API schema is a poor proxy for that deficiency. > > Since the exposure of a hint means nothing as far as its usefulness, I don't > think we should be codifying them as part of our API schema at this time. > At some point I imagine we'll evolve a more useful API for passing > information to the scheduler as part of a request, and when that happens I > don't think needing to support a myriad of meaningless hints in older API > versions is going to be desirable. > > Finally, at this time I'm not sure we should take the stance that only > in-tree scheduler hints are supported. While I completely agree with the > desire to expose things in cross-cloud ways as we've done and are looking to > do with flavor and image properties I think scheduling is an area where we > want to allow some flexibility for deployers to write and expose scheduling > capabilities that meet their specific needs. Over time I hope we will get > to a place where some standardization can happen, but I don't think locking > in the current scheduling hints is the way forward for that. I would love > to hear from multi-cloud users here and get some input on whether that's > crazy and they are expecting benefits from validation on the current > scheduler hints. > > Now, objects. As part of the work to formalize the request spec sent to the > scheduler there's an effort to make a scheduler hints object. This > formalizes them in the same way as the API with no benefit that I can see. > I won't duplicate my arguments above, but I feel the same way about the > objects as I do with the API. I don't think needing to update and object > version every time a new hint is added is useful at this time, nor do I > think we should lock in the current in-tree hints. > > In the end this boils down to my concern that the scheduling hints api is a > really horrible user experience and I don't want it to be solidified in the > API or objects yet. I think we should re-examine how they're handled before > that happens. Now we are discussing this on https://review.openstack.org/#/c/217727/ for allowing out-of-tree scheduler-hints. When we wrote API schema for scheduler-hints, it was difficult to know what are available API parameters for scheduler-hints. Current API schema exposes them and I guess that is useful for API users also. One idea is that: How about auto-extending scheduler-hint API schema based on loaded schedulers? Now API schemas of "create/update/resize/rebuild a server" APIs are auto-extended based on loaded extensions by using stevedore library[1]. I guess we can apply the same way for scheduler-hints also in long-term. Each scheduler needs to implement a method which returns available API parameter formats and nova-api tries to get them then extends scheduler-hints API schema with them. That means out-of-tree schedulers also will be available if they implement the method. # In short-term, I can see "blocking additionalProperties" validation disabled by the way. Thanks Ken Ohmichi --- [1]: https://github.com/openstack/nova/blob/master/doc/source/api_plugins.rst#json-schema __________________________________________________________________________ OpenStack Development Mailing List (not for usage questions) Unsubscribe: openstack-dev-requ...@lists.openstack.org?subject:unsubscribe http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-dev