Ruby SDK Reference

This topic explains how to use the Harness Feature Flags (FF) SDK in your Ruby application.

NOTE

This SDK works with Harness Self-Managed Enterprise Edition (on premises).

This topic describes how to use the Harness Feature Flags Ruby SDK for your Java application.

For getting started quickly, you can use our sample code from the Ruby SDK README. You can also clone and run a sample application from the Ruby SDK GitHub Repository.

Before you begin

You should read and understand the following:

• Feature Flags Overview

• Getting Started with Feature Flags

• Client-Side and Server-Side SDKs

• Communication Strategy Between SDKs and Harness Feature Flags

Version

Latest SDK version can be found on GitHub Release Page

Requirements

To use this SDK, make sure you:

• Install Ruby 2.7 or newer

• Download the SDK from our GitHub repository

• Create a Java application, or clone our sample application.

• Create a Feature Flag on the Harness Platform. If you are following along with the SDK README sample code, make sure your flag is called harnessappdemodarkmode

• Create an SDK key and make a copy of it

Install the SDK

Install the Ruby SDK using gem, for example:

gem install harness-featureflags

Or by adding the following snippet to your project's Gemfile file:

gem "ff-ruby-server-sdk"

Clone the SDK Repository

Run the following command to clone the Feature Flag SDK repository:

git clone --recurse-submodules [e-mail]:harness/ff-ruby-server-sdk.git

Initialize the SDK

To initialize the Go SDK, you need to:

1. Add your Server SDK Key to connect to your Harness Environment.

2. (Optional) Configure the SDK options.

3. Pass in the Server SDK Key and configuration options.

4. Add a Target that you want to Evaluate against a Feature Flag.

Add the Server SDK Key

To connect to the correct Environment that you set up on the Harness Platform, you need to add the Server SDK Key from that Environment. For example:

key = "YOUR_API_KEY_GOES_HERE"

Configure the SDK

You can configure the following features of the SDK:

Name	Example	Description	Default Value
baseUrl	config_url("https://config.ff.harness.io/api/1.0")	The URL used to fetch Feature Flag Evaluations. When using the Relay Proxy, change this to: http://localhost:7000	https://config.ff.harness.io/api/1.0
eventUrl	event_url("https://events.ff.harness.io/api/1.0")	The URL for posting metrics data to the Feature Flag service. When using the Relay Proxy, change this to: http://localhost:7000	https://events.ff.harness.io/api/1.0
pollInterval	poll_interval_in_seconds(60)	The interval in seconds that we poll for changes when you are using stream mode.	60 (seconds)
streamEnabled	stream_enabled(true)	Set to true to enable streaming mode.Set to false to disable streaming mode.	true
analyticsEnabled	analytics_enabled(true)	Set to true to enable analytics.Set to false to disable analytics.Note: When enabled, analytics data is posted every 60 seconds.	true

For further configuration options and samples, such as configuring your logger or using the SDK with the Relay Proxy, go to Additional Options.

Complete the initialization

Complete the initialization by creating an instance of the Feature Flag client and passing in the Server SDK Key and any configuration options. For example:

client.init(key, config)

Add a Target

What is a Target?

Targets are used to control which users see which Variation of a Feature Flag, for example, if you want to do internal testing, you can enable the Flag for some users and not others. When creating a Target, you give it a name and a unique identifier. Often Targets are users but you can create a Target from anything that can be uniquely identified, such as an app or a machine.

For more information about Targets, go to Targeting Users With Flags.

To add a Target, build it and pass in arguments for the following:

Parameter	Description	Required?	Example
identifier	Unique ID for the Target.Read Regex requirements for Target names and identifiers below for accepted characters.	Required	identifier="HT_1"
name	Name for this target. This does not have to be unique. Note: If you don’t provide a value, Harness generates the name based on the ID. Read Regex requirements for target names and identifiers below for accepted characters.	Optional Note: If you don't want to send a name, don't send the parameter. Sending an empty argument causes an error.	("Harness_Target_1")
attributes	Additional data you can store for a Target, such as email addresses or location.	Optional	attributes={"email": "[e-mail]"})

Regex requirements for Target names and identifiers

Identifier

Regex: ^[A-Za-z0-9.@_-]*$ Must consist of only alphabetical characters, numbers, and the following symbols: . (period) @ (at sign) -(dash) _ (underscore)

The characters can be lowercase or uppercase but cannot include accented letters, for example Cafe_789.

Name Regex: ^[\\p{L}\\d .@_-]*$

Must consist of only alphabetical characters, numbers, and the following symbols: . (period) @ (at sign) -(dash) _ (underscore) (space)

The characters can be lowercase or uppercase and can include accented letters, for example Café_123.

For example:

target = Target.new("Harness_Target_1", identifier="HT_1", attributes={"email": "[e-mail]"})

Evaluate a Flag

Evaluating a Flag is when the SDK processes all Flag rules and returns the correct Variation of that Flag for the Target you provide.

If a matching Flag can’t be found, or the SDK can’t remotely fetch flags, the default value is returned.

There are different methods for the different Variation types and for each method you need to pass in:

• Identifier of the Flag you want to evaluate

• The Target object you want to evaluate against

• The default Variation

For example:

Evaluate a string Variation

def string_variation(identifier, target, default_value)

Evaluate a boolean Variation

def bool_variation(identifier, target, default_value)

Evaluate a number Variation

def number_variation(identifier, target, default_value)

Evaluate a JSON Variation

def json_variation(identifier, target, default_value)

Test your app is connected to Harness

When you receive a response showing the current status of your Feature Flag, go to the Harness Platform and toggle the Flag on and off. Then, check your app to verify if the Flag Variation displayed is updated with the Variation you toggled.

NOTE

The SDK must run for at least 60 seconds before it sends metrics. Please ensure metrics have not been disabled in the SDK.

Close the SDK client

In most applications, you won't need to close the SDK client.

However, you should close the SDK client if:

• Your application is about to terminate. Closing the client ensures that all associated resources are released.

• You have determined that you do not need to evaluate flags again in your application lifecycle.

IMPORTANT

The SDK does not evaluate flags after the client is closed.

To close the SDK client:

• Assuming you have initialized an SDK client instance named client, call the following function:

  client.close()

Additional options

Use the Relay Proxy

When using your Feature Flag SDKs with a Harness Relay Proxy you need to change the default URL and events URL to http://localhost:7000 when initializing the SDK. For example:

config = ConfigBuilder.new  
                      .config_url("https://config.feature-flags.uat.harness.io/api/1.0")  
                      .event_url("https://event.feature-flags.uat.harness.io/api/1.0")  
                      .build

Use our public API methods

Our Public API exposes the following methods that you can use for instantiating, initializing, and closing the SDK:

def initialize(api_key = nil, config = nil, connector = nil)

def init(api_key = nil, config = nil, connector = nil)

def wait_for_initialization

def close

Sample code for a Ruby application

Here is a sample code for using the Feature Flag Ruby SDK:

require "logger"  
require "securerandom"  
  
require_relative '../lib/ff/ruby/server/sdk/dto/target'  
require_relative '../lib/ff/ruby/server/sdk/api/config'  
require_relative '../lib/ff/ruby/server/sdk/api/cf_client'  
require_relative '../lib/ff/ruby/server/sdk/api/config_builder'  
  
flag_b = "flag1"  
flag_n = "flag2"  
flag_s = "flag3"  
flag_j = "flag4"  
  
clients = {}  
targets = {}  
  
logger = Logger.new(STDOUT)  
  
executor = Concurrent::FixedThreadPool.new(100)  
  
keys = {  
  
  "Freemium" => "1f3339b4-e004-457a-91f7-9b5ce173eaaf",  
  "Non-Freemium" => "a30cf6aa-67f2-4545-8ac7-f86709f4f3a0"  
}  
  
keys.each do |name, key|  
  
  targets[name] = Target.new("ruby_target_" + name)  
  
  config = ConfigBuilder.new  
                        .logger(logger)  
                        .build  
  
  client = CfClient.new(key, config)  
  
  # .config_url("https://config.feature-flags.uat.harness.io/api/1.0")  
  # .event_url("https://event.feature-flags.uat.harness.io/api/1.0")  
  
  client.init  
  
  config.logger.debug "We will wait for the initialization"  
  
  client.wait_for_initialization  
  
  config.logger.debug "Initialization is complete"  
  
  clients[name] = client  
end  
  
iterations = 10  
  
counted = 0  
count_to = keys.size * iterations  
  
logger.debug "To count: " + count_to.to_s  
  
keys.each do |name, key|  
  
  client = clients[name]  
  target = targets[name]  
  
  executor.post do  
  
    (1..iterations).each do |iteration|  
  
      logger.debug name + " :: iteration no: " + iteration.to_s  
  
      bool_result = client.bool_variation(flag_b, target, false)  
      number_result = client.number_variation(flag_n, target, -1)  
      string_result = client.string_variation(flag_s, target, "unavailable !!!")  
      json_result = client.json_variation(flag_j, target, JSON.parse("{}"))  
  
      logger.debug name + " :: '" + flag_b.to_s + "' has the value of: " + bool_result.to_s  
      logger.debug name + " :: '" + flag_n.to_s + "' has the value of: " + number_result.to_s  
      logger.debug name + " :: '" + flag_s.to_s + "' has the value of: " + string_result.to_s  
      logger.debug name + " :: '" + flag_j.to_s + "' has the value of: " + json_result.to_s  
      logger.debug "- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -"  
  
      counted = counted + 1  
  
      logger.debug "Counted: " + counted.to_s  
  
      sleep 10  
    end  
  end  
end  
  
while counted != count_to  
  
  sleep(1)  
end  
  
clients.each do |name, client|  
  
  logger.debug name + " :: closing"  
  
  client.close  
end  

Troubleshooting

The SDK logs the following codes for certain lifecycle events, for example authentication, which can aid troubleshooting.

Code	Description
1000	Successfully initialized
1001	Failed to initialize due to authentication error
1002	Failed to initialize due to a missing or empty API key
2000	Successfully authenticated
2001	Authentication failed with a non recoverable error
2002	Authentication failed and is retrying
2003	Authentication failed and max retries have been exceeded
4000	Polling service started
4001	Polling service stopped
5000	Streaming service started
5001	Streaming service stopped
5002	Streaming event received
5003	Streaming disconnected and is retrying to connect
5004	Streaming stopped
6000	Evaluation was successfully
6001	Evaluation failed and the default value was returned
7000	Metrics service has started
7001	Metrics service has stopped
7002	Metrics posting failed
7003	Metrics posting success