[Engine-devel] FeatureSupported and compatibility versions

[Shireesh Anjal]

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:

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)

Thoughts?

Regards,
Shireesh