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Ruby Server SDK

Statsig server SDK for Ruby applications. This SDK is open source and hosted on github.

The Basics

Get started in a few quick steps.

  1. Create a free account on
  2. Install the SDK
  3. Initialize the SDK
  4. Fetch Feature Gates, Dynamic Configs, or Experiments
  5. Log a custom event

Step 1 - Create a free account on

You could skip this for now, but you will need an SDK Key and some Feature Gates or Dynamic Configs to use with the SDK in just a minute.

Step 2 - Install the SDK

If you are using Bundler, add the gem to your Gemfile from command line:

bundle add statsig

or directly include it in your Gemfile and run bundle install:

gem "statsig", ">= 1.8.3"

# check out the latest versions on

Step 3 - Initialize the SDK

After installation, you will need to initialize the SDK using a Server Secret Key from the statsig console.


Do NOT embed your Server Secret Key in client side applications, or expose it in any external facing documents. However, if you accidentally exposed it, you can create a new one in Statsig console.

There is also an optional parameter options that allows you to pass in a StatsigOptions to customize the SDK.

require 'statsig'


// Or, if you want to initialize with certain options
options ={'tier' => 'staging'})
Statsig.initialize('server-secret-key', options)

Initializing Statsig in a Rails Application

If your application is using Rails, you should initialize Statsig in config/initializers/statsig.rb:

Statsig.initialize('server-secret-key', options)

Initializing Statsig when using Unicorn, Puma, or Passenger web server

For Unicorn, you should initialize Statsig within an after_fork hook in your unicorn.rb config file:

after_fork do |server,worker|
Statsig.initialize('server-secret-key', options)

For Puma, you should initialize Statsig within an on_worker_boot hook in your puma.rb config file:

on_worker_boot do
Statsig.initialize('server-secret-key', options)

For Passenger, you should initialize Statsig in your config file:

if defined?(PhusionPassenger)
PhusionPassenger.on_event(:starting_worker_process) do |forked|
Statsig.initialize('server-secret-key', options)

initialize will perform a network request. After initialize completes, virtually all SDK operations will be synchronous1--the SDK will fetch updates from Statsig in the background, independently of your API calls.

Step 4 - Fetch Feature Gates, Dynamic Configs, or Experiments

Now that your SDK is initialized, let's fetch a Feature Gate. Feature Gates can be used to create logic branches in code that can be rolled out to different users from the Statsig Console. Gates are always CLOSED or OFF (think return false;) by default.

From this point on, all APIs will require you to specify the user (see Statsig user) associated with the request. For example, check a gate for a certain user like this:

user ={'userID' => 'some_user_id'})
if Statsig.check_gate(user, 'use_new_feature')
// Gate is on, enable new feature
// Gate is off

Feature Gates can be very useful for simple on/off switches, with optional but advanced user targeting. However, if you want to be able send a different set of values (strings, numbers, and etc.) to your clients based on specific user attributes, e.g. country, Dynamic Configs can help you with that. The API is very similar to Feature Gates, but you get an entire json object you can configure on the server and you can fetch typed parameters from it. For example:

config = Statsig.get_config(user, 'awesome_product_details')

// The 2nd parameter is the default value to be used in case the given parameter name does not exist on
// the Dynamic Config object. This can happen when there is a typo, or when the user is offline and the
// value has not been cached on the client.
item_name = config.get('product_name', 'Awesome Product v1');
price = config.get('price', 10.0);
shouldDiscount = config.get('discount', false);

// Or just get the whole json object backing this config if you prefer
json = config.value

Then we have Experiments, which you can use to run A/B/n experiments and use advanced features like layers (coming soon) to avoid collision and enable quicker iterations with parameter reuse.

expConfig = Statsig.get_experiment(user, 'new_user_promo');

promoTitle = expConfig.get('title', 'Welcome to Statsig! Use discount code WELCOME10OFF for 10% off your first purchase!');
discount = expConfig.get('discount', 0.1);


price = msrp * (1 - discount);
Asynchronous APIs

We mentioned earlier that after calling initialize most SDK APIs would run synchronously, so why are getConfig and checkGate asynchronous?

The main reason is that older versions of the SDK might not know how to interpret new types of gate conditions. In such cases the SDK will make an asynchronous call to our servers to fetch the result of a check. This can be resolved by upgrading the SDK, and we will warn you if this happens.

For more details, read our blog post about SDK evaluations. If you have any questions, please ask them in our Feedback Repository.

Step 5 - Log a custom event

Now that you have a Feature Gate or an Experiment set up, you may want to track some custom events and see how your new features or different experiment groups affect these events. This is super easy with Statsig - simply call the Log Event API and specify the user and event name to log; you additionally provide some value and/or an object of metadata to be logged together with the event:

Statsig.log_event(user, 'add_to_cart', 'SKU_12345', { 'price' => '9.99', 'item_name' => 'diet_coke_48_pack' })

Statsig User

When calling APIs that require a user, you should pass as much information as possible in order to take advantage of advanced gate and config conditions (like country or OS/browser level checks), and correctly measure impact of your experiments on your metrics/events. The userID field is required because it's needed to provide a consistent experience for a given user (click here to understand further why it's important to always provide a userID).

Besides userID, we also have email, ip, userAgent, country, locale and appVersion as top-level fields on StatsigUser. In addition, you can pass any key-value pairs in an object/dictionary to the custom field and be able to create targeting based on them.

Have sensitive user PII data that should not be logged?

No problem, we have a solution for it! On the StatsigUser object we also have a field called privateAttributes, which is a simple object/dictionary that you can use to set private user attributes. Any attribute set in privateAttributes will only be used for evaluation/targeting, and removed from any logs before they are sent to Statsig server.

For example, if you have feature gates that should only pass for users with emails ending in "", but do not want to log your users' email addresses to Statsig, you can simply add the key-value pair { email: "" } to privateAttributes on the user and that's it!

Statsig Options

You can specify optional parameters with options when initializing.

  • environment: Hash, default nil
    • a Hash you can use to set environment variables that apply to all of your users in the same session and will be used for targeting purposes.
    • The most common usage is to set the "tier" (string), and have feature gates pass/fail for specific environments. The accepted values are "production", "staging" and "development", e.g. StatsigOptions.New({ 'tier' => 'staging' }).
  • api_url_base string, default ""
    • The base url to use for network requests from the SDK
  • rulesets_sync_interval: Number, default 10
    • The interval to poll for changes to your gate and config definition changes
  • idlists_sync_interval: Number, default 60
    • The interval to poll for changes to id lists
  • logging_interval_seconds: Number, default 60
    • The default interval to flush logs to Statsig servers
  • logging_max_buffer_size: Number, default 1000, can be set lower but anything over 1000 will be dropped on the server
    • The maximum number of events to batch before flushing logs to the server
  • local_mode: Boolean, default false
    • An option to restrict the sdk to not issue any network requests and only respond with default values (or local overrides)

Shutting down Statsig

Because we batch and periodically flush events, some events may not have been sent when your app/server shuts down. To make sure all logged events are properly flushed, you should tell Statsig to shutdown when your app/server is closing:



Type StatsigUser

export type StatsigUser = {
class StatsigUser
attr_accessor :user_id
attr_accessor :email
attr_accessor :ip
attr_accessor :user_agent
attr_accessor :country
attr_accessor :locale
attr_accessor :app_version
attr_accessor :statsig_environment
attr_accessor :custom_ids
attr_accessor :private_attributes

def initialize(user_hash)
@statsig_environment =
if user_hash.is_a?(Hash)
@user_id = user_hash['userID'] || user_hash['user_id']
@user_id = @user_id.to_s unless @user_id.nil?
@email = user_hash['email']
@ip = user_hash['ip']
@user_agent = user_hash['userAgent'] || user_hash['user_agent']
@country = user_hash['country']
@locale = user_hash['locale']
@app_version = user_hash['appVersion'] || user_hash['app_version']
@custom = user_hash['custom'] if user_hash['custom'].is_a? Hash
@statsig_environment = user_hash['statsigEnvironment']
@private_attributes = user_hash['privateAttributes'] if user_hash['privateAttributes'].is_a? Hash
custom_ids = user_hash['customIDs'] || user_hash['custom_ids']
@custom_ids = custom_ids if custom_ids.is_a? Hash

Type StatsigOptions

class StatsigOptions
attr_accessor :environment
attr_accessor :api_url_base
attr_accessor :rulesets_sync_interval
attr_accessor :idlists_sync_interval
attr_accessor :logging_interval_seconds
attr_accessor :logging_max_buffer_size
attr_accessor :local_mode
attr_accessor :data_store

def initialize(
rulesets_sync_interval: 10,
idlists_sync_interval: 60,
logging_interval_seconds: 60,
logging_max_buffer_size: 1000,
local_mode: false,
data_store: nil)


How do I run experiments for logged out users?

You can run experiments for arbitrary unit IDs (sessionID, groupID, etc), rather than at the userID level, if you choose. These custom unit IDs must be predefined in your Statsig project, and then selected in the Experiment creation flow. For more information, see our guide on experimenting on custom ID types

How can I mock or override the SDK for testing?

Starting in v1.12.0+, the ruby SDK supports localMode and overrides

  • localMode is a boolean parameter in StatsigOptions when initializing the SDK. It restricts all network traffic, so the SDK operates offline and only returns default or override values.
  • Statsig.override_gate(<gate_name>, <gate_value>); will override the given gate to the provided boolean value. Useful for forcing a particular code branch in tests
  • Statsig.override_config(<config_name>, <config_value_hash>); will override the given config (or experiment) to the provided hash value. Useful for forcing a particular experiment variant in tests