[ovirt-devel] Making event types backwards compatible?

[Juan Hernández]

On 05/30/2017 08:55 AM, Tomas Jelinek wrote:
> 
> 
> On Tue, May 30, 2017 at 7:20 AM, Michal Skrivanek <mskrivan at redhat.com
> <mailto:mskrivan at redhat.com>> wrote:
> 
>     > On 29 May 2017, at 11:44, Juan Hernández <jhernand at redhat.com <mailto:jhernand at redhat.com>> wrote:
>     >
>     >> On 05/29/2017 11:27 AM, Michal Skrivanek wrote:
>     >>
>     >>> On 29 May 2017, at 10:39, Juan Hernández <jhernand at redhat.com
>     <mailto:jhernand at redhat.com>> wrote:
>     >>>
>     >>> Hello,
>     >>>
>     >>> It has been recently requested that the API provides event types:
>     >>>
>     >>> [RFE] Expose event types to API
>     >>> https://bugzilla.redhat.com/1453170
>     <https://bugzilla.redhat.com/1453170>
>     >>>
>     >>> Currently the API provides the event code and description, for
>     example:
>     >>>
>     >>> <event href="/ovirt-engine/api/events/8021" id="8021">
>     >>>   <code>19</code>
>     >>>   <description>Host myhost failed to recover.</description
>     >>>   ...
>     >>> </event>
>     >>>
>     >>> There is no documentation of what is the meaning of codes,
>     except the
>     >>> source code of the engine itself. This forces some applications
>     to add
>     >>> their own code to name mapping. For example, the 'ovirt' Ruby
>     gem used
>     >>> by older versions of ManageIQ to interact with oVirt contains
>     the following:
>     >>>
>     >>>
>     https://github.com/ManageIQ/ovirt/blob/v0.17.0/lib/ovirt/event.rb#L25-L485
>     <https://github.com/ManageIQ/ovirt/blob/v0.17.0/lib/ovirt/event.rb#L25-L485>
>     >>>
>     >>> We could avoid this by adding to the API a new event attribute that
>     >>> indicates the type:
>     >>>
>     >>> <event href="/ovirt-engine/api/events/8021" id="8021">
>     >>>   <code>19</code>
>     >>>   <type>host_recover_failure</type>
>     >>>   <description>Host myhost failed to recover.</description>
>     >>>   ...
>     >>> </event>
>     >>>
>     >>> Ideally this should be defined as an enum, so that it will be
>     >>> represented as an enum in the SDKs. Alternatively it could just
>     be an
>     >>> string, and we could reuse the 'name' attribute:
>     >>>
>     >>> <event href="/ovirt-engine/api/events/8021" id="8021">
>     >>>   <code>19</code>
>     >>>   <name>host_recover_failure</name>
>     >>>   <description>Host myhost failed to recover.</description>
>     >>>   ...
>     >>> </event>
>     >>>
>     >>> However, the key point to making this useful would be to keep
>     the types
>     >>> (or names) backwards compatible, so that users of the API can
>     rely on
>     >>> their values and meanings.
>     >>>
>     >>> So this is my question to you: can we commit to keep the names and
>     >>> meanings of the backend event types backwards compatible?
>     >>
>     >> Do we even have to make it bw compatible?
>     >> I guess it depends on the actual usage of those names…
>     >> The ovirt ruby gem itself doesn’t do much with it
>     >
>     > We need to make keep it backwards compatible or else tell users "don't
>     > rely on these values, as they may change without notice".
>     >
>     > The 'ovirt' gem doesn't do anything special, it just creates its own
>     > code to name mapping. But the users of the 'ovirt' gem (the ManageIQ
>     > oVirt provider) do rely on the name. For example:
>     >
>     >
>     > https://github.com/ManageIQ/manageiq-providers-ovirt/blob/master/app/models/manageiq/providers/redhat/infra_manager/event_parser.rb#L80-L92
>     <https://github.com/ManageIQ/manageiq-providers-ovirt/blob/master/app/models/manageiq/providers/redhat/infra_manager/event_parser.rb#L80-L92>
> 
> 
> hmmm, while we are on topic, this pretty much looks like that manageiq
> does not only rely on the code but also on the actual value of it since
> it is parsing it:
> 
> # sample message: "Interface nic1 (VirtIO) was added to VM v5. (User:
> admin at internal-authz)" message.split(/\s/)[7][0...-1]
> 
> Is this something we commit to maintain? Or should we commit to maintain it?
>

That is a good point, that isn't very future proof. We should also find
a way to make less fragile. Any suggestion?

> 
>     >
>     > That means that if we ever change the meaning of a code the ManageIQ
>     > provider, for example, will break.
> 
>     Right,then it indeed needs to stay stable.
>     But how is maintaining the enum string different from the code? It is
>     the same information, so if MIQ doesn't use the name directly then it
>     doesn't really matter if it's a code or string.
>     Perhaps deprecate the code and keep the name fixed?
> 
>     Thanks,
>     michal
> 
>     >
>     >>>
>     >>> Regards,
>     >>> Juan Hernandez
>     >>>
>     >>>
>     >>> _______________________________________________
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>     <http://lists.ovirt.org/mailman/listinfo/devel>
>     >
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