Features helps you to determine whether or not a feature should be made available to one or more users. You can choose one of the following ways:

• Enable a feature only for a specific set of users;
• Enable or disabled for a percentage of users;
• Disable a feature.

Also known as: feature switch, feature flag, feature toggle, ...

• Features is completely storage agnostic. You should be able to use your own storage, you just need to implement the Engine interface.
• This library comes with an in memory store, but it's basically used for testing. You should not use this in production.

• Javascript (in progress)
• Ruby (soon)
• Python (soon)

Create an instance of Features type passing the storage as an argument:

Features := features.New(memory.New())

Create an instance of Feature type with the desired parameters and save it:

feature := engine.FeatureFlag{
  Key:     "Feature X",
  Enabled: false,
  Users:   []*engine.User{&engine.User{Id: "alice@example.org"}},
  Percentage: 10,
}
Features.Save(feature)

Check if a feature is enabled:

Features.IsEnabled("Feature X")

Check if a feature is disabled:

Features.IsDisabled("Feature X")

Execute an anonymous function if the feature is enabled:

Features.With("Feature X", func() {
  fmt.Println("`Feature X` is enabled!")
})

Execute an anonymous function if the feature is disabled:

Features.Without("Feature X", func() {
  fmt.Println("`Feature X` is disabled!")
})

Check if a feature is active for a particular user:

Features.UserHasAccess("Feature X", "alice@example.org")

If you're rolling out a feature, you might want to enable it for a percentage of your users. There are two ways you can achieve that: Either enabling the feature for a percentage of users or disabling that.

• Enable the feature for a percentage of users:

feature := engine.FeatureFlag{
  Key:     "Feature X",
  Enabled: true,
  Percentage: 10,
}

• Disable the feature for a percentage of users:

feature := engine.FeatureFlag{
  Key:     "Feature X",
  Enabled: false,
  Percentage: 10,
}

You might want to enable a feature for a set of users to try out and give feedback on before it's rolled out for everyone. To achieve this, you need to specify the users by doing the following:

feature := engine.FeatureFlag{
  Key:     "Feature X",
  Enabled: true,
  Users:   []*engine.User{&engine.User{Id: "alice@example.org"}},
}

Features comes with an HTTP API that's used by the SDKs, but you should not expose that to the world because there's no authentication layer.

• POST /features - Create a new feature flag
• PUT /features/:feature-key - Update an existing feature flag
• DELETE /features/:feature-key - Delete an existing feature flag
• GET /features/:feature-key - Get an existing feature flag
• GET /features - List all feature flags
• PUT /features - Validate Access

curl -i http://localhost:8000/features -XPOST -d '{"key": "login-via-email", "percentage": 90, "enabled": true, "users": [{"id": "alice@example.org"}]}'

Response:

HTTP/1.1 201 Created
Content-Type: application/json
Date: Tue, 03 Nov 2015 23:21:07 GMT
Content-Length: 94

{"enabled":true,"key":"login-via-email","users":[{"id":"alice@example.org"}],"percentage":90}

curl -i http://localhost:8000/features/login-via-email -XPUT -d '{"key": "login-via-email", "percentage": 90, "enabled": false, "users": [{"id": "bob@example.org"}]}'

Response:

HTTP/1.1 200 OK
Content-Type: application/json
Date: Tue, 03 Nov 2015 23:22:05 GMT
Content-Length: 93

{"enabled":false,"key":"login-via-email","users":[{"id":"bob@example.org"}],"percentage":90}

curl -i http://localhost:8000/features/login-via-email -XDELETE

Response:

HTTP/1.1 204 No Content
Content-Type: application/json
Date: Tue, 03 Nov 2015 23:24:46 GMT

curl -i http://localhost:8000/features/login-via-email

Response:

HTTP/1.1 200 OK
Content-Type: application/json
Date: Tue, 03 Nov 2015 23:26:22 GMT
Content-Length: 94

{"enabled":true,"key":"login-via-email","users":[{"id":"alice@example.org"}],"percentage":90}

curl -i http://localhost:8000/features

Response:

{
  "items": [
    {
      "percentage": 90,
      "enabled": true,
      "users": [
        {
          "id": "alice@example.org"
        }
      ],
      "key": "login-via-email"
    }
  ],
  "item_count": 1
}

curl -i http://localhost:8000/features -XPUT -d '{"key": "login-via-email", "user": "alice@example.org"}'

Response for success:

HTTP/1.1 200 OK
Content-Type: application/json
Date: Wed, 04 Nov 2015 00:19:46 GMT
Content-Length: 0

Response for failure:

HTTP/1.1 403 Forbidden
Content-Type: application/json
Date: Wed, 04 Nov 2015 00:20:51 GMT
Content-Length: 0