----- Original Message -----
From: "Shireesh Anjal" <sanjal@redhat.com> To: "Mike Kolesnik" <mkolesni@redhat.com> Cc: engine-devel@ovirt.org Sent: Wednesday, March 20, 2013 4:47:08 PM Subject: Re: [Engine-devel] FeatureSupported and compatibility versions
On 03/18/2013 01:11 PM, Shireesh Anjal wrote:
On 03/18/2013 12:59 PM, Mike Kolesnik wrote:
----- Original Message -----
Hi all,
The current mechanism in oVirt to check whether a feature is supported in a particular compatibility version is to use the FeatureSupported class. e.g.
FeatureSupported.networkLinking(getVm().getVdsGroupCompatibilityVersion())
Checks whether the "network linking" feature is supported for the the VM's cluster compatibility version. This internally checks whether the value of the corresponding config (NetworkLinkingSupported) for the given compatibility version is true/false.
I'm not sure if this is a good idea, since a feature is typically supported "from" a particular version. E.g. Gluster support was introduced in 3.1, and it continues to be available in all subsequent versions. So I see no point in adding configuration for every version indicating whether the feature is supported in that version or not. I suggest to use either of the following options: You can "merge" the configs into a single config when older versions go out of the supported versions for the system.
i.e. in 4.0 you can have upgrade script that merges all GlusterFeatureSupported to one entry instead of several.
Why are we even storing this information in config? Is this something that can be "configured" at customer site?
As previously explained (but off list :) ) , Config gives you the ability to have a cachable "map" of entry (i.e - "feature name") per version and value. I guess it was convinient for the developers to use that. I also mentioned that customers/oVirt users should config the entries of vdc_options using engine-config tool only. Not all entries are exposed via engine-config.properties (and no, not just "is feature supported" entries are hidden).
1) Instead of using a boolean config for each version, use a single string config that indicates the "supported from" version e.g. GlusterSupportedFrom = 3.1. There could be rare cases where a feature, for some reason, is removed in some release. In such cases, we could use one additional config for the "supported to" version.
2) Continue with the boolean approach, but do not have entries for every version; rather make use of the "default value" for majority of cases, and add the explicit version mapping for the minority e.g. GlusterSupported = true by default, and false in case of 3.0 (only one config required for 3.0) I'm not sure why we would want to complicate this simple mechanism?
Is there much to gain?
I think option 1 suggested above is simpler - to implement as well as to understand.
Let me give you an example of why I don't like current mechanism. I introduce a version check for a feature that was introduced in 3.1. I'm being asked now to add three entries in config
3.0 - false 3.1 - true 3.2 - true
It will also mean that when 3.3 goes out, someone has to make sure that another entry is added for 3.3-true. I think it is not logical as well as scalable if you have more versions. And it sounds far more complex (to maintain) than just having
<Feature>SupportedFrom = 3.1
So I would like to know if there are any objections to my proposal. I intend to use this for at least the gluster related features.
Thoughts?
Regards, Shireesh _______________________________________________ Engine-devel mailing list Engine-devel@ovirt.org http://lists.ovirt.org/mailman/listinfo/engine-devel
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