Hi Bertrand Thanks. This looks like a promising start.
I have some comments, though ;-) 1. My first reaction to the SlingHttpServletRequest argument was: Why an argument ? Why not a ThreadLocal managed by the actual service with the help of a request filter ? (ok, what to do with non-request services). 2. I think the Providers should just register their known feature names as string-service properties. Could there be more than one supported feature actually ? Or is it really just a single one ? When using a service registration property we can start with single-string and switch to multi-value later without changing the API. 3. Configuration: This is a good point brought up by Dominik: We want to have central/singular configuration for the feature flags not spread them amongst tons of providers. And we have configuration which is global (static) and we have configuration which is per-user/group/time-of-day/random/whatever. 4. Thinking about it: these providers actually just evaluate an expression based on some configuration and some comparison object. Maybe there is a better term than „Provider“ for these things. 5. I understand FeatureFlags is actually the service we are interested in: - How about calling that just Feature with then call „Feature.isEnabled(FeatureX)“ then ? - We should expose the Feature Service in the SlingBindings - We should expose the Feature Service in the sling:defineObjects tag - we should probably expose the Feature Service in some sling:feature JSP tag 6. Re. Enums: On first sight this looks like a good idea. But it has the drawback that it generates a package wiring dependency and requires the ENUMs to be exported as API. What is the worst case szenarion of mis-typing a feature ? I think, the feature will just never be enabled. (ok, another one is that another unrelated feature might be enabled due to the typo — which could be mitigated by stipulating features to have reasonably distinct names). Regards Felix — Felix Meschberger | Principal Scientist | Adobe Am 13.11.2013 um 02:52 schrieb Bertrand Delacretaz <bdelacre...@apache.org>: > Hi, > > FYI I have created a minimal prototype [2] of how I'd see feature > flags in Sling, as suggested a while ago by Henry Saginor in > SLING-3148. > > The slides at [1], that Tommaso tweeted today, are full of good ideas > about this. > > -Bertrand > > [1] http://www.paulhammond.org/2010/06/trunk/alwaysshiptrunk.pdf > > [2] > https://svn.apache.org/repos/asf/sling/whiteboard/bdelacretaz/feature-flags
