Awesome

Quarantine

Quarantine is a tiny OTP application for feature toggles.

Currently it supports two strategies:

• whitelist list of ids that can access some feature
• percentage compute a score from the given id check with score <= percentage. Note that the combination of feature name and id produce a deterministic score

Setup

Add quarantine to your application deps

def deps do
  [
    {:quarantine, "~> 0.1.2"}
  ]
end

You can setup flags using config environment or provide a Quarantine.Driver to fetch configuration from an external source

When hardcoded config is good enough you can provide it as below

config :quarantine, 
   some_percentage_flag: 0.5,
   some_whitelist_flag: [1, 2, 3]
   other_whitelist_flag: ["08362804-bdc0-11e8-9407-24750000045e", "9fbc6c6e-f2dd-4f9d-8944-b81dd5a25fed"]

Usage

Simply call enabled?/2 where you want to split the control flow

Quarantine.enabled?(:some_percentage_flag, 1)
=> false

Quarantine.enabled?(:some_percentage_flag, 2)
=> true

Quarantine.enabled?(:some_whitelist_flag, 1)
=> true

Quarantine.enabled?(:some_whitelist_flag, 9)
=> false

When using percentage you can check current ids distribution if needed with scores/2

Quarantine.scores(:some_percentage_flag, [1, 2, 3])
=>  [{1, 0.9967498283360037},
     {2, 0.18811322194247349},
     {3, 0.30522621499961855}]

Testing

Flags can be enabled for a specific test with Quarantine.Server.start_link/1.

Quarantine.Server.start_link(feature1: [1], feature2: [3,4])

Refresh config without re-deploying your application

To do that you should provide an implementation of Quarantine.Driver that fetch flags configuration from a external source

Redis Driver example:

defmodule RedisDriver do
  @behaviour Quarantine.Driver

  def get_flags() do
    Redix.command!(:my_redix, ["GET", "my_flags"])
  end
end

S3 Driver example:

defmodule S3Driver do
  @behaviour Quarantine.Driver

  def get_flags() do
    "bucket"
    |> ExAws.S3.get_object("path")
    |> ExAws.request!()
  end
end

Then add it to :quarantine configuration:

config :quarantine, 
   driver: RedisDriver,
   poll_interval: 60_000 # in ms