[gioele]

> This misses the problem -- often, the new feature is buggy in ways that are not seen in the initial testing.

Indeed. The only good way to enable features gradually is to use a tool like GitHub Scientist [0] that exercises the new code path and records its effects but then uses the effects of the old code path in production. This allows weird edge cases to be found and dealt with before enabling the new feature.

[0] http://githubengineering.com/scientist/ Previous discussion: https://news.ycombinator.com/item?id=11027581

[pkaeding]

Yeah, I actually wrote about something similar recently (in the context of a database migration): http://blog.launchdarkly.com/feature-flagging-to-mitigate-ri...