This package is a server-side SDK for applications written in Ruby for the Tailslide feature flag framework.

Visit the https://github.com/tailslide-io repository or see Tailslide’s case study page for more information.

Install the Tailslide npm package with gem install tailslide

The FlagManagerclass is the entry point of this SDK. It is responsible for retrieving all the flag rulesets for a given app with its app_id and creating new Toggler instances to handle toggling of feature flags within that app. To instantiate a FlagManager object, a user must provide a configuration object:

require "async"
require('tailslide')

config = {
    nats_server: "nats://localhost:4222",
    nats_stream: "flags_ruleset",
    app_id: 1,
    user_context: "375d39e6-9c3f-4f58-80bd-e5960b710295",
    sdk_key: "myToken",
    redis_host: "http://localhost",
    redis_port: 6379,
}

Async do |task|
    manager = FlagManager.new(**config)
    manager.initialize_flags

end

• nats_server is the NATS JetStream server address:port
• nats_stream is the NATS JetStream’s stream name that stores all the apps and their flag rulesets
• app_id is the ID number of the app the user wants to retrieve its flag ruleset from
• user_context is the UUID string that identifies the current user
• sdk_key is the SDK key for the Tailslide, it is used as a password for NATS JetStream token authentication
• redis_host is the address to the Redis database
• redis_port is the port number that the Redis database runs on

After instantiating a FlagManager, invoke the initialize method. This method connects the FlagManager instance to both NATS JetStream and Redis Timeseries, and asynchronously retrieves the latest and any new flag ruleset data.

Once the FlagManager is initialized, it can create a Toggler, with the new_toggler method, for each feature flag that the developer wants to wrap the new and old features in. A Toggler’s is_flag_active method checks whether the flag with its flag_name is active or not based on the flag ruleset. A Toggler’s is_flag_active method returns a boolean value, which can be used to evaluate whether a new feature should be used or not.

flag_config = {
    flag_name: 'App 1 Flag 1',
}

flag_toggler = manager.new_toggler(flag_config)

if flag_toggler.is_flag_active
    # call new feature here
else
    # call old feature here
end

To use a Toggler instance to record successful or failed operations, call its emit_success or emit_failure methods:

if successCondition
    flag_toggler.emit_success
else
    flag_toggler.emit_failure
end

The FlagManager class is the entry point of the SDK. A new FlagManager object will need to be created for each app.

Parameters:

• An object with the following keys
  • nats_server is the NATS JetStream server address:port
  • nats_stream is the NATS JetStream’s stream name that stores all the apps and their flag rulesets
  • app_id a number representing the application the microservice belongs to
  • sdk_key a string generated via the Tower front-end for NATS JetStream authentication
  • user_context a string representing the user’s UUID
  • redis_host a string that represents the url of the Redis server
  • redis_port a number that represents the port number of the Redis server

Asynchronously initialize flagmanager connections to NATS JetStream and Redis database

Parameters:

• nil

Return Value:

• nil

Set the current user's context for the flagmanager

Parameters:

• new_user_context: A UUID string that represents the current active user

Return Value:

• nil

Returns the current user context

Parameters:

• nil

Return Value:

• The UUID string that represents the current active user

Creates a new toggler to check for a feature flag's status from the current app's flag ruleset by the flag's name.

Parameters:

• options: An object with key of flag_name and a string value representing the name of the feature flag for the new toggler to check whether the new feature is enabled

Return Value:

• A Toggler object

Asynchronously disconnects the FlagManager instance from NATS JetStream and Redis database

Parameters:

• nil

Return Value:

• nil

The Toggler class provides methods that determine whether or not new feature code is run and handles success/failure emissions. Each toggler handles one feature flag, and is created by flagmanaer.new_toggler().

Checks for flag status, whitelisted users, and rollout percentage in that order to determine whether the new feature is enabled.

• If the flag's active status is false, the function returns false
• If current user's UUID is in the whitelist of users, the function returns true
• If current user's UUID hashes to a value within user rollout percentage, the function returns true
• If current user's UUID hashes to a value outside user rollout percentage, the function returns false

Parameters:

• nil

Return Value

• true or false depending on whether the feature flag is active

Records a successful operation to the Redis Timeseries database, with key flagId:success and value of current timestamp

Parameters:

• nil

Return Value

• nil

Records a failure operation to the Redis Timeseries database, with key flagId:success and value of current timestamp

Parameters:

• nil

Return Value

• nil