Ask HN: Does your team use feature flags? • Hacker News Board

Re: Ask HN: Does your team use feature flags?

#91

Post by dboreham » Fri, Jan 28, 2022, 6:50 PM UTC

TillE wrote: post #57

mcv wrote: post #8

I haven't seen them used on any of the projects I've worked on. HN is really the only place I regularly hear about feature flags, actually.

HN seems like 90% web developers, and I don't really see the point outside of the web. I mean, we have other ways of gradually rolling out and configuring new software builds.

I've used them going back decades, long before they were a buzzword, only in back-end. The most common use case is where you have a bug fix or new feature that is highly data-specific. Often you'll have a user or set of users with the problematic data pattern. You code up a fix and redeploy, but with the fix disabled. Then enable the fixed code path for the user that reported the problem and ask them to re-test. From their feedback and/or log data you can confirm the fix and then enable for all users. This is helpful for example when there would be privacy issues debugging/testing a fix on real user data.

Re: Ask HN: Does your team use feature flags?

#92

Post by CSDude » Fri, Jan 28, 2022, 6:50 PM UTC

Old company used to because deployment after merge took a day with hundreds of developers deploying a monolith. 1/3 of the incidents were related to misuse of feature flags. It definitely has its places, but letting turn into a hammer to apply it everywhere is wasteful and risk. Totally depends on the application and customer base though.

Re: Ask HN: Does your team use feature flags?

#93

Post by neebz » Fri, Jan 28, 2022, 6:57 PM UTC

Yes. Feature flags changed the mindset of my whole team. I absolutely love the fact that it pushes the whole team towards release-small-release-often mentality. It's a technical solution with many benefits but I love the cultural impact the most.

Re: Ask HN: Does your team use feature flags?

#94

Post by 8note » Fri, Jan 28, 2022, 6:57 PM UTC

drclau wrote: post #32

Worked for a bigtech well known name, large and extremely important project, literally the core of a service serving an enormous number of users, and feature flags were mandatory, no exceptions. I can't imagine working without feature flags. Being able to enable new features in particular deployment rings (canary, dogfood, various production rings or regions), or per users / user groups, enabling gradually (percentag…

I turned off a giant old service that was full of feature flags once.

Having them everywhere was great, we could flip things off feature by feature just by changing the flags.

Having the old ones still around can be handy.

Re: Ask HN: Does your team use feature flags?

#95

Post by NicoJuicy » Fri, Jan 28, 2022, 6:58 PM UTC

Yeah.

It's almost a requirement to do continuous deployment and working without long living branches.

Don't forget to clean them up with you don't need one anymore. There's work involved with that too.

Re: Ask HN: Does your team use feature flags?

#96

Post by alunchbox » Fri, Jan 28, 2022, 6:59 PM UTC

neebz wrote: post #93

Yes. Feature flags changed the mindset of my whole team. I absolutely love the fact that it pushes the whole team towards release-small-release-often mentality. It's a technical solution with many benefits but I love the cultural impact the most.

We're currently in the transition, any chance you have some insights to help ease the mentality shift as the team transitions to this vs bi-weekly/monthly deployments.

Re: Ask HN: Does your team use feature flags?

#97

Post by danzdance » Fri, Jan 28, 2022, 7:00 PM UTC

I think they are a necessary evil. I haven't seen a better mechanism to allow dynamic changes to production, but they come with a big downside for operations.

The problem with feature flags is that (assuming a flag can only be "on" or "off") once you introduce the flags you have 2^n different possible states the system can be in. When you have a bug or a crash, you have to reason about all of those states. If you have even 10 flags, that's over 1,000 combinations!

Does anyone have a different way of enabling "experiments" or quickly rolling back bad changes?

Re: Ask HN: Does your team use feature flags?

#98

Post by dr_dshiv » Fri, Jan 28, 2022, 7:01 PM UTC

Do you use any tools, like LaunchDarkly, for the feature flagging?

Re: Ask HN: Does your team use feature flags?

#99

Post by hinkley » Fri, Jan 28, 2022, 7:06 PM UTC

jasonpeacock wrote: post #19

Not just feature flags, but "knobs" - we use a percentage (of requests or customers) instead of a boolean to enable features so we can dial them up/down. This let us slowly roll out new features to a subset of users in case there are any issues. Using feature flags also requires testing the default (not enabled state), ensuring you have a robust realtime configuration manager to control the knobs, and metrics for eve…

See also https://en.m.wikipedia.org/wiki/Knight_Capital_Group the Therac-25 of feature toggles.

Re: Ask HN: Does your team use feature flags?

#100

Post by capableweb » Fri, Jan 28, 2022, 7:09 PM UTC

the-alt-one wrote: post #11

capableweb wrote: post #7

Earlier quoted context omitted.

That's A/B testing, not feature flags. Check https://news.ycombinator.com/item?id=30115276 for a description of how feature flags are used.

A/B testing can be done with feature flags. Gradual rollout, specific customer opt-in, and so on.

I guess you could do A/B testing with feature flags but honestly, it won't be any good. If you want a good answer if to go with A or B, you want to have many data points, not just from one specific customer.

Gradual rollout and specific customer opt-in to certain features can certainly be done with feature flags, I wouldn't call that A/B testing unless you're running experiments and reaching a conclusion that A is better than B (or vice-versa).