[openstack-dev] [nova] [placement] [operators] Optional resource asking or not?

Sylvain Bauza sbauza at redhat.com
Mon Jan 23 14:18:35 UTC 2017



Le 23/01/2017 15:11, Jay Pipes a écrit :
> On 01/22/2017 04:40 PM, Sylvain Bauza wrote:
>> Hey folks,
>>
>> tl;dr: should we GET /resource_providers for only the related resources
>> that correspond to enabled filters ?
> 
> No. Have administrators set the allocation ratios for the resources they
> do not care about exceeding capacity to a very high number.
> 
> If someone previously removed a filter, that doesn't mean that the
> resources were not consumed on a host. It merely means the admin was
> willing to accept a high amount of oversubscription. That's what the
> allocation_ratio is for.
> 
> The flavor should continue to have a consumed disk/vcpu/ram amount,
> because the VM *does actually consume those resources*. If the operator
> doesn't care about oversubscribing one or more of those resources, they
> should set the allocation ratios of those inventories to a high value.
> 
> No more adding configuration options for this kind of thing (or in this
> case, looking at an old configuration option and parsing it to see if a
> certain filter is listed in the list of enabled filters).
> 
> We have a proper system of modeling these data-driven decisions now, so
> my opinion is we should use it and ask operators to use the placement
> REST API for what it was intended.
> 

I know your point, but please consider mine.
What if an operator disabled CoreFilter in Newton and wants to upgrade
to Ocata ?
All of that implementation being very close to the deadline makes me
nervous and I really want the seamless path for operators now using the
placement service.

Also, like I said in my bigger explanation, we should need to modify a
shit ton of assertions in our tests that can say "meh, don't use all the
filters, but just these ones". Pretty risky so close to a FF.

-Sylvain


> Best,
> -jay
> 
>> Explanation below why even if I
>> know we have a current consensus, maybe we should discuss again about it.
>>
>>
>> I'm still trying to implement https://review.openstack.org/#/c/417961/
>> but when trying to get the functional job being +1, I discovered that we
>> have at least one functional test [1] asking for just the RAMFilter (and
>> not for VCPUs or disks).
>>
>> Given the current PS is asking for *all* both CPU, RAM and disk, it's
>> trampling the current test by getting a NoValidHost.
>>
>> Okay, I could just modify the test and make sure we have enough
>> resources for the flavors but I actually now wonder if that's all good
>> for our operators.
>>
>> I know we have a consensus saying that we should still ask for both CPU,
>> RAM and disk at the same time, but I imagine our users coming back to us
>> saying "eh, look, I'm no longer able to create instances even if I'm not
>> using the CoreFilter" for example. It could be a bad day for them and
>> honestly, I'm not sure just adding documentation or release notes would
>> help them.
>>
>> What are you thinking if we say that for only this cycle, we still try
>> to only ask for resources that are related to the enabled filters ?
>> For example, say someone is disabling CoreFilter in the conf opt, then
>> the scheduler shouldn't ask for VCPUs to the Placement API.
>>
>> FWIW, we have another consensus about not removing
>> CoreFilter/RAMFilter/MemoryFilter because the CachingScheduler is still
>> using them (and not calling the Placement API).
>>
>> Thanks,
>> -Sylvain
>>
>> [1]
>> https://github.com/openstack/nova/blob/de0eff47f2cfa271735bb754637f979659a2d91a/nova/tests/functional/test_server_group.py#L48
>>
>>
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