Molasses

A feature toggle library using redis or SQL (using Ecto) as a backing service. It allows you to roll out to users based on a percentage. Alternatively, you can use Molasses to deploy to a group of users or user ids.

Installation

1. Add molasses to your list of dependencies in mix.exs and run mix deps.get:

def deps do
  [{:molasses, "~> 0.2.0"}]
end

2. Install related dependencies by including ExRedis, MongoDB or Ecto and one of its adapter libraries for Postgres or Mysql.

2A. Redis

For Redis, you will just need to include exredis:

def deps do
  [
    {:molasses, "~> 0.2.0"},
    {:exredis, ">= 0.2.4"}
  ]
end

2B. SQL using Ecto

For Ecto with PostgreSQL, install ecto and postgrex. You will also need to start ecto and postgrex as applications:

def deps do
  [
    {:molasses, "~> 0.2.0"},
    {:ecto, "~> 2.1.1"},
    {:postgrex, ">= 0.0.0"}
  ]
end

def application do
  [applications: [:ecto, :postgrex]]
end

Your config will also need to change. You will need to set up an Ecto Repo like you would here. As well as set the Molasses adapter to postgres.

# molasses adapter setting
config :molasses, adapter: "ecto"

You will need to create an ecto migration and add the features tables.

  defmodule Repo.CreateTestMocks do
    use Ecto.Migration

    def change do
      create table(:features) do
        add :name, :string
        add :percentage, :integer
        add :users, :string
        add :active, :boolean
      end

      create index(:features, [:name])
    end
  end

2C. MongoDB

def deps do
  [
    {:molasses, "~> 0.2.0"},
    {:mongodb, ">= 0.0.0"},
  ]
end

For a working example of how to set up Molasses look at Molasses Example

Usage

Molasses uses the same interface whether you are using Redis or SQL. Each function takes an Ecto.Repo or the ExRedis client as the first argument.

Activate

• activate/2 - Activates a feature for all users.
• activate/3 - Activates a feature for some users.
  • When the last argument is an integer then it sets the feature active for a percentage of users.
  • When the last argument is a string then it sets a feature active for that specific user or user group.
  • When the last argument is a list then it sets a feature active for that specific list of users or user groups

Deactivate

• deactivate/2 - Dectivates a feature for all users.

Checking to see if a feature is active

• is_active/2 - Check to see if a feature is active for all users.
• is_active/3 - Check to see if a feature is active for a specific user.

Examples

Redis

# Create a new redis client
{:ok, client} = Exredis.start_link

# activate a feature
Molasses.activate(client, "my_feature")

# activate a feature for a percentage of users
Molasses.activate(client, "my_feature", 75)

# activate a feature for a subset of integer based userIds
Molasses.activate(client, "my_feature", [2, 4, 5])

# activate a feature for a subset of string based userIds (think a mongoId) or a list of groups
Molasses.activate(client, "my_feature", ["admins", "super admins"])

# activate a feature for only one group of users
Molasses.activate(client, "my_feature", "powerusers")

# checking if a feature is active for all users
Molasses.is_active(client, "my_feature")

# checking if a feature is active for a specific user (based on percentage, or user id/group)
Molasses.is_active(client, "my_feature", identifier)

# deactivate a feature
Molasses.deactivate(client, "my_feature")

Ecto

# Switched to ecto as my adapter
Application.put_env(:molasses,:adapter, "ecto")

# alias the Repo for use
alias Molasses.Test.Repo

# use is_active and activate the same way but it uses the Ecto repo instead of
Molasses.activate(Repo, "my_feature", 75)
Molasses.is_active(Repo, "my_feature")

MongoDB

# Switched to ecto as my adapter
Application.put_env(:molasses,:adapter, "mongo")


# Create a new mongo client
{:ok, conn} = Mongo.start_link(database: "molasses")


# use is_active and activate the same way but it uses the Ecto repo instead of
Molasses.activate(conn, "my_feature", 75)
Molasses.is_active(conn, "my_feature")