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:

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

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

2A. Redis

For Redis, you will just need to include `exredis`: 

```elixir
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:

```elixir
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](https://hexdocs.pm/ecto/Ecto.html#module-repositories). As well as set the Molasses adapter to postgres. 

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

For a working example of how to set up Molasses look at [Molasses Example](https://github.com/securingsincity/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")