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I see these changes as really important.

We need to establish good patterns other SDKs can copy.

On 24 April 2015 at 12:05, Alex Xu <soulxu at gmail.com> wrote:
> 2015-04-24 18:15 GMT+08:00 Andrey Kurilin <akurilin at mirantis.com>:
>> >When user execute cmd without --os-compute-version. The nova client
>> > should discover the nova server >supported version. Then cmd choice the
>> > latest version supported both by client and server.
>>
>> In that case, why X-Compute-API-Version can accept "latest" value? Also,
>> such discovery will require extra request to API side for every client call.
>>
>
> I think it is convenient for some case. like give user more easy to try nova
> api by some code access the nova api directly. Yes, it need one more extra
> request. But if without discover, we can't ensure the client support server.
> Maybe client too old for server even didn't support the server's min
> version. For better user experience, I think it worth to discover the
> version. And we will call keystone each nova client cli call, so it is
> acceptable.

We might need to extend the API to make this easier, but I think we
need to come up with a simple and efficient pattern here.


Case 1:
Existing python-novaclient calls, now going to v2.1 API

We can look for the transitional entry of computev21, as mentioned
above, but it seems fair to assume v2.1 and v2.0 are accessed from the
same service catalog entry of "compute", by default (eventually).

Lets be optimistic about what the cloud supports, and request "latest"
version from v2.1.

If its a v2.0 only API endpoint, we will not get back a version header
with the response, we could error out if the user requested v2.x
min_version via the CLI parameters.

In most cases, we get the latest return values, and all is well.


Case 2:
User wants some info they know was added to the response in a specific
microversion

We can request "latest" and error out if we don't get a new enough
version to meet the user's min requirement.


Case 3:
Adding support for a new request added in a microversion

We could just send "latest" and assume the new functionality, then
raise an error when you get bad request (or similar), and check the
version header to see if that was the cause of the problem, so we can
say why it failed.

If its supported, everything just works.

If the user requests a specific version before it was supported, we
should error out as not supported, I guess?

In a way it would be cleaner if we had a way for the client to say
"latest but requires 2.3", so you get a bad version request if your
minimum requirement is not respected, so its much clearer than
miss-interpreting random errors that you might generate. But I guess
its not totally required here.


Would all that work? It should avoid an extra API call to discover the
specific version we have available.

>> >'--os-compute-version=None' can be supported, that means will return the
>> > min version of server supported.
>>
>> From my point of view '--os-compute-version=None' is equal to not
>> specified value. Maybe, it would be better to accept value "min" for
>> os-compute-version option.
>
> I think '--os-compute-version=None' means not specified version request
> header when send api request to server. The server behavior is if there
> isn't value specified, the min version will be used.

--os-compte-version=v2 means no version specified I guess?

Can we go back to the use cases here please?
What do the users need here and why?


>> >3. if the microversion non-supported, but user call cmd with
>> > --os-compute-version, this should return failed.
>>
>> Imo, it should be implemented on API side(return BadRequest when
>> X-Compute-API-Version header is presented in V2)

V2 is already deployed now, and doesn't do that.

No matter what happens we need to fix that.
>
> Emm.... I'm not sure. Because GET '/v2/' already can be used to discover
> microversion support or not. Sounds like add another way to support
> discover? And v2 api didn't return fault with some extra header, that sounds
> like behavior and back-incompatible change.

-1

We should not use the URL to detect the version.
We have other ways to do that for a good reason.

Thanks,
John



>> On Fri, Apr 24, 2015 at 12:42 PM, Alex Xu <soulxu at gmail.com> wrote:
>>>
>>>
>>>
>>> 2015-04-24 17:24 GMT+08:00 Andrey Kurilin <akurilin at mirantis.com>:
>>>>
>>>> Thank you for suggestions! I'll try modify patches as soon as possible.
>>>
>>>
>>> np, it's better waiting for more comment before you begin to update the
>>> code first. avoid you need rework again I think :)
>>>
>>>>
>>>>
>>>> On Fri, Apr 24, 2015 at 6:56 AM, Alex Xu <soulxu at gmail.com> wrote:
>>>>>
>>>>> Thanks Andrey for hard work on the microverison client support.
>>>>>
>>>>> Wrote down some my thought:
>>>>>
>>>>> I also agreed we will have only one endpoint 'compute'. Hope we can
>>>>> switch v2.1 export as '/v2' in the api-paste.conf as default very soon~
>>>>>
>>>>> let's say what expected after we only have v2.1 in the world first:
>>>>>
>>>>> There are two cases for use nova client.
>>>>> 1. user use nova client command line. I think command line should
>>>>> support version discover. Provide most convenient way let the user try nova.
>>>>> 2. user use nova client as library. user should call the client code to
>>>>> discover the version and decided what version he want to use by himself.
>>>>>
>>>>> For the command line, the behavior can be:
>>>>>
>>>>> When user execute cmd without --os-compute-version. The nova client
>>>>> should discover the nova server supported version. Then cmd choice the
>>>>> latest version supported both by client and server. This is good for us to
>>>>> introduce the new feature to the user.
>>>>>
>>>>> Also user can specified a version he want to by --os-compute-version.
>>>>>
>>>>> '--os-compute-version=None' can be supported, that means will return
>>>>> the min version of server supported.
>>>>>
>>>>> The supported version can be discovered by version API (Thanks to
>>>>> Ken'ichi fix this):
>>>>> GET '/'
>>>>>
>>>>> https://github.com/openstack/nova/blob/master/doc/api_samples/versions/versions-get-resp.json#L25
>>>>>
>>>>> But reality is the v2 and v2.1 will existed at same time.
>>>>>
>>>>> So the v2 or v2.1 code both can run under the endpoint 'compute' with
>>>>> url '/v2'. It depend on the admin's deployment.
>>>>>
>>>>> So I think the cmd also can discover whether the api supported
>>>>> microversion under the 'compute' endpoint.
>>>>>
>>>>> This can be discovered by version api also.
>>>>>
>>>>> GET '/v2/' will return the endpoint version info. Then we can check the
>>>>> version and min_version properties to know whether the api support
>>>>> microversion or not.
>>>>>
>>>>> The behavior can be:
>>>>> 1. If the microversion supported, the cmd behavior is same as the
>>>>> description at the top of this mail
>>>>> 2. If the microversion non-supported, user call cmd without
>>>>> --os-compute-version, we use the min version.
>>>>> 3. if the microversion non-supported, but user call cmd with
>>>>> --os-compute-version, this should return failed.
>>>>>
>>>>> Hope those thoughts are helpful.
>>>>>
>>>>> Looks like this need some change in current patchset also :( I know
>>>>> Andrey already pay lot of on this. But if we like this way, I also can give
>>>>> some help on the coding :)
>>>>>
>>>>> Thanks
>>>>> Alex
>>>>>
>>>>>
>>>>> 2015-04-10 19:30 GMT+08:00 Andrey Kurilin <akurilin at mirantis.com>:
>>>>>>
>>>>>> Hi all!
>>>>>> I working on implementation of support microversions in novaclient.
>>>>>> Patches are ready for review, but there is one opened question: what we
>>>>>> should do with v2.1 endpoint(computev21 service type)?
>>>>>>
>>>>>> "compute" is a default value of service type and keystone returns v2
>>>>>> api endpoint for it(at least in devstack), so version header will be ignored
>>>>>> on API side.
>>>>>>
>>>>>> On the one hand, each deployment can have it's own configuration of
>>>>>> service catalog and endpoints, so default value of service type should be
>>>>>> strict and support as much deployments as we can. On the other hand,
>>>>>> dependency of service type for microversion feature is not good and
>>>>>> end-users should not take care about choice of correct service type when
>>>>>> they want to execute simple command.
>>>>>>
>>>>>> Possible solutions:
>>>>>>
>>>>>> leave everything as is: use "--service-type computev21" for each
>>>>>> microversioned command
>>>>>> move default value of service type to environment variables(default
>>>>>> value is hardcoded in novaclient code now)
>>>>>> add additional option --compute-api-type. Proposed etherpad by
>>>>>> Christopher Yeoh
>>>>>> https://etherpad.openstack.org/p/novaclient_microversions_design .
>>>>>> Implementation is already finished -
>>>>>> https://review.openstack.org/#/c/167577/ . This proposal still requires
>>>>>> addition cli option, but compute-api-type looks more user-friendly
>>>>>>
>>>>>>
>>>>>> Current implementation uses "compute" as default value for service
>>>>>> type. Patches are pass all gates, except stable branches and ready for
>>>>>> review:
>>>>>>
>>>>>> https://review.openstack.org/#/c/169378/  - deprecate v1.1 and remove
>>>>>> references to v3 in code
>>>>>> https://review.openstack.org/#/c/152569/  - Implements 'microversions'
>>>>>> api type - Part 1 (usage of
>>>>>> nova.api.openstack.api_version_request:APIVersionRequest class with
>>>>>> https://review.openstack.org/#/c/169292/ )
>>>>>> https://review.openstack.org/#/c/167408/  - Implements 'microversions'
>>>>>> api type - Part 2 (adds new decorators and substitution mechanism using
>>>>>> nova.api.openstack.versioned_method )
>>>>>> https://review.openstack.org/#/c/136458/  - Implementation of 2.2
>>>>>> microversion
>>>>>>
>>>>>>
>>>>>> --
>>>>>> Best regards,
>>>>>> Andrey Kurilin.
>>>>>>
>>>>>>
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>>>>>>
>>>>>
>>>>>
>>>>>
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>>>>
>>>>
>>>>
>>>> --
>>>> Best regards,
>>>> Andrey Kurilin.
>>>>
>>>>
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>>
>>
>> --
>> Best regards,
>> Andrey Kurilin.
>>
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