Question 1

How do I set up FunWithFlags with a Phoenix application?

Accepted Answer

Configure the persistence adapter (e.g., Redis or Ecto with your repo) and PubSub adapter (Redis or Phoenix.PubSub) in config.exs. For Phoenix.PubSub, ensure the pubsub server is started in your supervision tree and referenced in the FunWithFlags config, as detailed in the 'PubSub Adapters' section.

Question 2

FunWithFlags vs Flipper: which is better for Elixir?

Accepted Answer

FunWithFlags is designed for Elixir with better performance due to ETS caching and distributed sync, while Flipper is a Ruby gem ported to Elixir. FunWithFlags minimizes database load and is more reliable in distributed environments, but Flipper might be familiar if coming from a Ruby background.

Question 3

Can I use FunWithFlags without Redis?

Accepted Answer

Yes, you can use the Ecto adapter with PostgreSQL, MySQL, or SQLite for persistence, and Phoenix.PubSub for notifications, eliminating the need for Redis entirely. This is configured in the 'Persistence Adapters' section.

Question 4

How to implement A/B testing with percentage gates in FunWithFlags?

Accepted Answer

Use the percentage-of-actors gate to enable a feature for a deterministic percentage of users based on their actor ID hash. This ensures consistent exposure for the same users across requests, ideal for gradual rollouts, as explained in the 'Percentage of Actors Gate' examples.

Question 5

What happens if the PubSub notification system fails?

Accepted Answer

FunWithFlags has a configurable TTL for the ETS cache (default 900 seconds), so flags will be reloaded from persistence after the timeout. However, nodes might serve stale data temporarily until the next cache refresh, as noted in the caching discussion.

Question 6

How to handle multi-tenancy with FunWithFlags and Ecto?

Accepted Answer

When using Ecto with multi-tenancy, you must modify your repo's prepare_query callback to skip org_id checks for FunWithFlags queries, which are annotated with a custom :fun_with_flags option, as described in the 'Ecto Multi-tenancy' section.

fun_with_flags

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