[Engine-devel] Fwd: Custom properties per device + vNIC profile = not working (< 3.3)

Thu Nov 21 17:39:21 UTC 2013

----- Original Message -----
> From: "Mike Kolesnik" <mkolesni at redhat.com>
> To: "Itamar Heim" <iheim at redhat.com>
> Cc: engine-devel at ovirt.org
> Sent: Wednesday, November 20, 2013 9:41:45 AM
> Subject: Re: [Engine-devel] Fwd: Custom properties per device + vNIC profile = not working (< 3.3)
> 
> ----- Original Message -----
> > On 11/20/2013 09:31 AM, Mike Kolesnik wrote:
> > >
> > > ----- Original Message -----
> > >> On 11/20/2013 09:07 AM, Mike Kolesnik wrote:
> > >>> ----- Original Message -----
> > >>>> On 11/11/2013 11:48 AM, Mike Kolesnik wrote:
> > >>>>>
> > >>>>> ----- Original Message -----
> > >>>>>> Hi Mike,
> > >>>>>>
> > >>>>>> ----- Original Message -----
> > >>>>>>> From: "Mike Kolesnik" <mkolesni at redhat.com>
> > >>>>>>> To: "engine-devel" <engine-devel at ovirt.org>
> > >>>>>>> Cc: "Barak Azulay" <bazulay at redhat.com>, "Martin Perina"
> > >>>>>>> <mperina at redhat.com>, "Livnat Peer" <lpeer at redhat.com>,
> > >>>>>>> "Itamar Heim" <iheim at redhat.com>
> > >>>>>>> Sent: Monday, November 11, 2013 8:49:33 AM
> > >>>>>>> Subject: Custom properties per device + vNIC profile = not working
> > >>>>>>> (<
> > >>>>>>> 3.3)
> > >>>>>>>
> > >>>>>>> Hi,
> > >>>>>>>
> > >>>>>>> I came across a situation where I wanted to define custom
> > >>>>>>> properties
> > >>>>>>> on
> > >>>>>>> a
> > >>>>>>> vNIC profile sitting under a network in a 3.2 data center.
> > >>>>>>>    From what I saw the configuration value for custom properties
> > >>>>>>> (CustomDeviceProperties) is split into 4, one per each version
> > >>>>>>> (3.0,
> > >>>>>>> 3.1,
> > >>>>>>> 3.2, 3.3).
> > >>>>>>> Since vNIC profile is located under the DC tree, it takes the DC
> > >>>>>>> version
> > >>>>>>> -
> > >>>>>>> 3.2 in this specific case.
> > >>>>>>
> > >>>>>> Custom Device Properties were designed to be specified for each
> > >>>>>> cluster
> > >>>>>> version
> > >>>>>> independently, it doesn't care about DC version. AFAIK cluster
> > >>>>>> version
> > >>>>>> defines
> > >>>>>> what features are available ...
> > >>>>>>
> > >>>>>>>
> > >>>>>>> I tried to set the config value for 3.2 but got:
> > >>>>>>> $ engine-config -s
> > >>>>>>> CustomDeviceProperties="{type=interface;prop={myProp=[a-zA-Z0-9-]+}}"
> > >>>>>>> --cver=3.2
> > >>>>>>> Cannot set value {type=interface;prop={myProp=[a-zA-Z0-9-]+}} to
> > >>>>>>> key
> > >>>>>>> CustomDeviceProperties. Device custom properties are not supported
> > >>>>>>> in
> > >>>>>>> version 3.2
> > >>>>>>>
> > >>>>>>> This is already not very good, since in a 3.2 DC there can be 3.3
> > >>>>>>> clusters
> > >>>>>>> with 3.3 hosts that do support custom device properties.
> > >>>>>>
> > >>>>>> Specify your properties for 3.3 version, since they will be used in
> > >>>>>> 3.3
> > >>>>>> clusters ...
> > >>>>>>
> > >>>>>
> > >>>>> But the effective version is the DC version as I explained.
> > >>>>>
> > >>>>> In a DC 3.0-3.3 I can have clusters which the minimal version is the
> > >>>>> DC
> > >>>>> version, and the maximal version is 3.3.
> > >>>>> For example I can have the following:
> > >>>>> DC - version 3.0
> > >>>>>     + Cluster 1 - version 3.0
> > >>>>>     + Cluster 2 - version 3.1
> > >>>>>     + Cluster 3 - version 3.2
> > >>>>>     + Cluster 4 - version 3.3
> > >>>>>
> > >>>>> In this constellation, I could use custom device properties only on
> > >>>>> Cluster
> > >>>>> 4, but it's not possible to define them since the vNIC profile is
> > >>>>> using
> > >>>>> the DC version 3.0.
> > >>>>> So effectively this feature is not usable to me unless I use a 3.3
> > >>>>> DC.
> > >>>>>
> > >>>>>>>
> > >>>>>>> I also tried to alter the config value in the DB directly, but the
> > >>>>>>> custom
> > >>>>>>> properties code ignored it since custom properties are not
> > >>>>>>> supported
> > >>>>>>> in
> > >>>>>>> 3.2.
> > >>>>>>> So, de facto, I have no reasonable way as a user to define custom
> > >>>>>>> device
> > >>>>>>> properties to use for my vNIC profiles in DC < 3.3.
> > >>>>>>
> > >>>>>> There are two configuration properties  for Custom Device
> > >>>>>> Properties:
> > >>>>>>
> > >>>>>> 1) SupportCustomDeviceProperties
> > >>>>>>         - defines in what version properties are supported
> > >>>>>>         - cannot be altered by users of course
> > >>>>>>
> > >>>>>> 2) CustomDeviceProperties
> > >>>>>>         - holds properties specification for each version
> > >>>>>>         - can be defined using engine-config
> > >>>>>>
> > >>>>>>>
> > >>>>>>> I opened the bug
> > >>>>>>> https://bugzilla.redhat.com/show_bug.cgi?id=1028757
> > >>>>>>> for
> > >>>>>>> this, however I also want to discuss the situation:
> > >>>>>>
> > >>>>>> I looked at the bug and the problem is, that management network
> > >>>>>> profile
> > >>>>>> is bound to DC and not the Cluster. And that's something we never
> > >>>>>> thought
> > >>>>>> of
> > >>>>>> ...
> > >>>>>>
> > >>>>>>>
> > >>>>>>> 1. As a user, I can't set custom properties for level < 3.3 which
> > >>>>>>> is
> > >>>>>>> not
> > >>>>>>> good.
> > >>>>>>
> > >>>>>> Well, it's 3.3 feature, so it looks OK for me
> > >>>>>>
> > >>>>>>> Removing the blocking, and loading custom properties for all
> > >>>>>>> versions
> > >>>>>>> would
> > >>>>>>> fix the bug and allow using custom device properties for older
> > >>>>>>> versions,
> > >>>>>>> the
> > >>>>>>> reasonable place to block this would be running a VM (or plugging a
> > >>>>>>> device).
> > >>>>>>> Basically this is the lesser issue..
> > >>>>>>>
> > >>>>>>> 2. I just don't see the added value of splitting the definition of
> > >>>>>>> the
> > >>>>>>> properties per level..
> > >>>>>>
> > >>>>>> The idea behind the version splitting was:
> > >>>>>>
> > >>>>>> 1) We have a device with a feature that doesn't work correctly with
> > >>>>>> version
> > >>>>>> 3.3,
> > >>>>>>       but it's fixed in 3.4
> > >>>>>> 2) By specifying custom property per version we cane disable this
> > >>>>>> feature
> > >>>>>> for
> > >>>>>> 3.3
> > >>>>>>       and enable for 3.4
> > >>>>>
> > >>>>> Custom properties is not for specifying which features are enabled,
> > >>>>> there
> > >>>>> is a whole other mechanism for that..
> > >>>>>
> > >>>>> Custom properties is for hooks (and other possible extensions), which
> > >>>>> by
> > >>>>> definition are not something that is guaranteed to exist so I see no
> > >>>>> point
> > >>>>> to force the user to update multiple configurations and cause
> > >>>>> confusion
> > >>>>> for him..
> > >>>>
> > >>>> as martin explained, we have predefined custom properties, which are
> > >>>> based on the vdsm version, and hence are actually features we know to
> > >>>> expose or not to expose.
> > >>>> user-defined custom properties - are up to the admin, but we let these
> > >>>> be at cluster level as well to allow more granularity.
> > >>>
> > >>> There are no predefined properties here, only user defined properties.
> > >>>
> > >>>>
> > >>>>>
> > >>>>>>
> > >>>>>>> The custom properties are extensions which might or might not be
> > >>>>>>> available
> > >>>>>>> to
> > >>>>>>> a certain VM, I don't see how having different sets of custom
> > >>>>>>> properties
> > >>>>>>> per
> > >>>>>>> version (what version, DC version, cluster version?) would make any
> > >>>>>>> difference - either the VM can utilize the extension given some
> > >>>>>>> state
> > >>>>>>> of
> > >>>>>>> the
> > >>>>>>> system, or it can't, but the determining factor is not the version
> > >>>>>>> but
> > >>>>>>> rather the availability of the extension.
> > >>>>>>> For example, I can have a hook for vNIC altering some property
> > >>>>>>> installed
> > >>>>>>> on
> > >>>>>>> host A and not host B, if the VM runs on host A it will get this
> > >>>>>>> capability
> > >>>>>>> and on host B it won't, regardless the DC version the VM is in.
> > >>>>>>>
> > >>>>>>> This is not to say we shouldn't block custom properties on the
> > >>>>>>> engine-VDSM
> > >>>>>>> API level since it's only available since 3.3, but this is handled
> > >>>>>>> by
> > >>>>>>> another config value (SupportCustomDeviceProperties) which is not
> > >>>>>>> alterable
> > >>>>>>> by the user.
> > >>>>>>> So basically, I think splitting the value per version is over
> > >>>>>>> complication
> > >>>>>>> and see no added value to the users, just more maintenance should
> > >>>>>>> they
> > >>>>>>> choose to use this feature.
> > >>>>>>>
> > >>>>>>> Your thoughts please.
> > >>>>>>
> > >>>>>> AFAIK only network and storage team wanted to use device custom
> > >>>>>> properties
> > >>>>>> in 3.3 version, but I'm not sure what's current usage status.
> > >>>>>>
> > >>>>>> But IMHO it's too late for 3.3 to change specification ...
> > >>>>>
> > >>>>> Since I can have cluster 3.3 in a DC < 3.3, and this is the upgrade
> > >>>>> path
> > >>>>> for existing users,
> > >>>>> I'd argue that the bug is severe enough and should be fixed asap even
> > >>>>> for
> > >>>>> 3.3 versions.
> > >>>>
> > >>>> please note that if you expose this at cluster level and not DC level,
> > >>>> you need to make sure to verify it when moving a VM between clusters
> > >>>> in
> > >>>> same DC.
> > >>>> also, if this is somehow related to logical networks, not vnic
> > >>>> specific,
> > >>>> than logical networks are DC level entities.
> > >>>>
> > >>>>
> > >>>
> > >>> OK but my point was that a custom properties is not meant to be split
> > >>> by
> > >>> versions since
> > >>> by definition of it, a hook might or might not exist on a given host
> > >>> (regardless of the host version).
> > >>> It only imposes more strain on the user to define possible custom
> > >>> properties by version..
> > >>>
> > >>> I see no value to users in this approach, only more work and
> > >>> unclearness..
> > >>>
> > >>> Mind you, hook is not a "feature" that is explicitly supported on a
> > >>> given
> > >>> version, but an extension
> > >>> mechanism which can have 3rd party extensions that might or might not
> > >>> exist
> > >>> on a given host, but this
> > >>> won't stop an action from occurring (i.e. VM would still start if a
> > >>> hook
> > >>> is
> > >>> missing but some custom
> > >>> property was sent).
> > >>>
> > >>> Also the original bug still exists because even though the vNIC is
> > >>> sitting
> > >>> at VM which is in cluster
> > >>> (thus in effect having access to the cluster version), the profile sits
> > >>> under network (which, as you
> > >>> mention, is DC level entity).
> > >>> So for the user using a DC < 3.3 there is no option to use this feature
> > >>> even though he can have 3.3
> > >>> clusters in his DC.
> > >>>
> > >>
> > >> except some hooks are shipped as required, and some custom properties
> > >> are supported by vdsm even without hooks.
> > >> so allowing to specify they are 'there' for a specific vdsm version is
> > >> useful.
> > >>
> > >
> > > Seems to me you're referring to things that should be in a predefined
> > > properties
> > > list, which as I mentioned doesn't exist for this feature.
> > >
> > 
> > 1. maybe it should.
> > 2. still, i think the granularity isn't hurting in this case - more
> > likely a hook will be needed, or not needed, in specific compat versions
> > as features are added/removed from the product, even for custom hooks.
> > 
> 
> Since it's not possible for me to predict the future, I'd argue that
> simplicity is the best
> way to begin with, and if there is such demand in the future then we can
> always change the
> code to handle the more complicated use cases.
> 
> IMHO, since currently there is no usage of this feature except vNIC profiles
> which is half
> usable due to the limitations imposed, seems fair to me to go with a simple
> value which is
> version agnostic and let the admin try this feature out.
> 
> If we get requests to make this more specific then a proper design,
> accommodating the specific
> requirements that will be raised, can be thought of and implemented. The
> current design doesn't
> fit the single use case for this feature that we have.

I understand your point on this option could have been used on different DC levels as well (as long as the clluster level is still 3.3),
but I don't see a real reason at this point to move away from the assumption of new features exist only in the new DC level introduced by the version.

Thanks
Barak

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