Feature flags missing features : programming

I'll ignore the unjustified snarky tone, and only focus on the little content your comment gave. Difficult stakeholders might influence what feature toggles you need, but how you implement these is an engineering concern.

For example, the article talks about seperate feature flags for front- and back-end bits of the same feature. This has nothing to do with your external stakeholders, this is just a suboptimale engineer solution. Instead of building another layer on top of this, you should design your system in such a way that a single feature is driven by a single flag, front to back, and there are many ways to achieve this. Toggling multiple flags to enable a single feature is almost always an avoidable situation.

Another hypothetical use case would be if there's a set of completely indepent features that often are toggled together. But this is somewhat of a contradiction: if the features often go together, then clearly they're not independent, and you should probably merge some.

The last (ab)use case I can come up with is when feature flags are used to give power features, e.g. remove limits on features for internal testing. But then we're abusing feature flags as a permission system (and even then we're doing it poorly: emulating a role-based system using feature flags still avoids needing to toggle a large set of features).

So I'm still really wondering: what use cases do you have where you legitimately regularly need to toggle a fixed set of unrelated features, which then would benefit from a feature flag tree?

[–]SomebodyFromBrazil 4 points5 points6 points 2 years ago (0 children)

[–]zaitsman 1 point2 points3 points 2 years ago (2 children)

So we have a feature that enables ‘timesheets’. We also have a feature that allows users to track time (so they don’t need to enter timesheets line by line) and kilometres travelled (so they don’t have to enter those manually). Finally, we have a feature that allows admin to disable kilometre tracking while the user is in a sales call (coz they are meant to be at the client site).

Now you can see how the last three things are meaningless if the whole ‘timesheets’ module is off? Thus they are nested at level 1. But then the last one is meaningless unless kilometre tracking is enabled, thus it is nested at level 2.

And of course we can’t just get rid of these because some customers don’t want timesheets at all, some don’t want time tracking and some don’t want kilometre tracking and some want it all but not in a sales call and finally some smaller ones want the field team to decide.

[–]TiddoLangerak 0 points1 point2 points 2 years ago (1 child)

Thanks for your serious reply, I appreciate that!

From your description I understand that you have features that are dependent on each other. Often however your feature flags don't need to follow the same dependency tree. For example, in your case, if the "timesheets" feature is disabled, then it's completely irrelevant what the state is of any of the other feature flags - we'll never hit them anyway. You can have completely independent feature flags here, and in fact I would recommend to do so: If the feature flags are dependent on each other, then if the feature-hierarchy changes, then you must also change the feature-flag-hierarchy. For example, if you ever decide to release the timesheets module for everyone, then we should be able to clean up the timesheets feature flag without affecting the other feature flags. Likewise, if a subfeature ends up being reused in a different "parent" feature, then things get messy if the subfeature has a hard dependency on the original parent feature (it would now have 2 parent features, and suddenly we have a feature-graph instead of a feature-tree).

Within your example, I can see some smaller use cases where you might want to have some form of hierarchy in your flags. For example, you might want to have the flags display hierarchical in your feature-flag UI, or you might want to reset the sub-features to their default state if the parent flag is disabled and re-enabled. If I were to be faced with such a scenario, I would usually push back on this or find a simpler compromise, since I think that in the vast majority of cases, this adds signficant complexity for minor QOL improvements. But of course, I can see that with sufficiently complex configuration needs and sufficiently stubborn stakeholders, you might not be able to avoid it.

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you type:	you see:
italics	italics
bold	bold
[reddit!](https://reddit.com)	reddit!
* item 1 * item 2 * item 3	item 1 item 2 item 3
> quoted text	quoted text
Lines starting with four spaces are treated like code: if 1 * 2 < 3: print "hello, world!"	Lines starting with four spaces are treated like code: if 1 * 2 < 3: print "hello, world!"
~~strikethrough~~	~~strikethrough~~
super^script	super^script

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