----- Original Message -----
From: "Adam Litke" agl@us.ibm.com To: "Saggi Mizrahi" smizrahi@redhat.com Cc: vdsm-devel@lists.fedorahosted.org, "Vinzenz Feenstra" vfeenstr@redhat.com Sent: Monday, January 14, 2013 5:21:41 PM Subject: Re: [vdsm] API Documentation & Since tag
On Mon, Jan 14, 2013 at 12:37:57PM -0500, Saggi Mizrahi wrote:
----- Original Message -----
From: "Adam Litke" agl@us.ibm.com To: "Vinzenz Feenstra" vfeenstr@redhat.com Cc: vdsm-devel@lists.fedorahosted.org Sent: Friday, January 11, 2013 9:03:19 AM Subject: Re: [vdsm] API Documentation & Since tag
On Fri, Jan 11, 2013 at 10:19:45AM +0100, Vinzenz Feenstra wrote:
Hi everyone,
We are currently documenting the API in vdsmapi-schema.json I noticed that we have there documented when a certain element newly is introduced using the 'Since' tag. However I also noticed that we are not documenting when a field was newly added, nor do we update the 'since' tag.
We should start documenting in what version we've introduced a field. A suggestion by saggi was to add to the comment for example: @since: 4.10.3
What is your point of view on this?
I do think it's a good idea to add this information. How about supporting multiple Since lines in the comment like the following made up example:
## # @FenceNodePowerStatus: # # Indicates the power state of a remote host. # # @on: The remote host is powered on # # @off: The remote host is powered off # # @unknown: The power status is not known # # @sentient: The host is alive and powered by its own metabolism # # Since: 4.10.0 - @FenceNodePowerStatus # Since: 10.2.0 - @sentient ##
I don't like the fact that both lines don't point to the same type of token. I also don't like that it's a repeat of the type names and field names.
I prefer Vinzenz original suggestion (on IRC) of moving the "Since" token up and then have it be a state. It also makes discerning what entities you can use up to a certain version easier if you make sure to keep them sorted.
We can do this because the order of the fields and availability is undetermined (unlike real structs).
That is not correct. These structures are parsed into an OrderedDict and the ordering is important (especially for languages like C which might use real structs).
The "wire" format, json, ignores the ordering, further more, for languages like C we can't use actual structs because then we have to bump a major version every time we add a field as the sizeof(struct Foo) changed.
## # @FenceNodePowerStatus: # # Indicates the power state of a remote host. # # Since: 4.10.0 # # @on: The remote host is powered on # # @off: The remote host is powered off # # @unknown: The power status is not known # # Since: 10.2.0 # # @sentient: The host is alive and powered by its own metabolism # ##
The problem though is that it makes since a property of the fields and not of the struct. This isn't that much of a problem as we can assume the earliest version is the time when the struct was introduced.
I don't like this any better than my suggestion. Aside from the fact that field ordering is important (in the data structure itself), this spreads the since information throughout the comment rather than concentrating it in a single place.
Well, thinking about it, I don't understand why structs need to have a "Since" property anyway. Only verbs should have it. Structs are available (by inference) since the earliest call that produces them.
All fields in a struct are optional anyway. Old versions wouldn't try and access them, new clients should always assume these fields may not be returned anyway.
-- Adam Litke agl@us.ibm.com IBM Linux Technology Center