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Ruby Server SDK

Getting Started

The following will outline how to get up and running with Statsig for Ruby.

Create an Account

To work with the SDK, you will need a Statsig account. If you don't yet have an account, you can sign up for a free one here. You could skip this for now, but you will need an SDK key and some gates/experiments to use with the SDK in just a minute.


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", ">= X.Y.Z"

Check out the latest versions on

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 named 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'}, network_timeout: 5)

# And a callback when the initialization network request fails
def error_callback(e)
puts e

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

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, Passenger, or Sidekiq

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)

For Sidekiq, you should initialize Statsig in your sidekiq.rb/server configuration file:

Sidekiq.configure_server do |config|
config.on(:startup) do

config.on(:shutdown) do

If you are using Rails in combination with any of the above, you should be sure to initialize using the specific process lifecycle hooks exposed by the respective tool. You can initialize in multiple places, which should ensure the SDK is fully usable including all background processing.

initialize will perform a network request. After initialize completes, virtually all SDK operations will be synchronous (See Evaluating Feature Gates in the Statsig SDK). The SDK will fetch updates from Statsig in the background, independently of your API calls.

Working with the SDK

Checking a Gate

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

Reading a Dynamic Config

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

Getting an Layer/Experiment

Then we have Layers/Experiments, which you can use to run A/B/n experiments. We offer two APIs, but we recommend the use of layers to enable quicker iterations with parameter reuse.

# Values via getLayer

layer = Statsig.get_layer(user, "user_promo_experiments")
title = layer.get("title", "Welcome to Statsig!")
discount = layer.get("discount", 0.1)

# or, via getExperiment

title_exp = Statsig.get_experiment(user, "new_user_promo_title")
price_exp = Statsig.get_experiment(user, "new_user_promo_price")

title = title_exp.get("title", "Welcome to Statsig!")
discount = price_exp.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.

Logging an 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:

'price' => '9.99',
'item_name' => 'diet_coke_48_pack'

Retrieving Feature Gate Metadata

In certain scenarios, it's beneficial to access detailed information about a feature gate, such as its current state for a specific user or additional contextual data. This can be accomplished effortlessly through the Get Feature Gate API. By providing the necessary user details and the name of the feature gate you're interested in, you can fetch this metadata to inform your application's behavior or for analytical purposes.

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.

Private Attributes

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)
  • bootstrap_values: String, default nil
    • a string that represents all rules for all feature gates, dynamic configs and experiments. It can be provided to bootstrap the Statsig server SDK at initialization in case your server runs into network issue or Statsig server is down temporarily.
  • rules_updated_callback: function, default nil
    • a callback function that's called whenever we have an update for the rules; it's called with a logical timestamp and a JSON string (used as is for bootstrapValues mentioned above). Note that as of v0.6.0, this will be called from a background thread that the SDK uses to update config values.
  • data_store: IDataStore, default nil
    • A data store with custom storage behavior for config specs. Can be used to bootstrap Statsig server (takes priority over bootstrap_values). Can also be used to continously fetch updates in place of the Statsig network. See Data Stores.
  • user_persistent_storage: IUserPersistentStorage default nil
    • A persistent storage adapter for running sticky experiments.
  • network_timeout: Number, default nil
    • Maximum number of seconds to wait for a network call before timing out.

Shutting Statsig Down

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:


Client SDK Bootstrapping | SSR v0.13.0+

The Ruby server SDK, starting in 0.13.0 supports generating the initializeValues needed to bootstrap a Statsig Client SDK preventing a round trip to Statsig servers. This can also be used with web [statsig-js, statsig-react] SDKs to perform server side rendering (SSR).
values = Statsig.get_client_initialize_response(user); # Hash[String, Any] | Nil

Working with IP or UserAgent Values

This will not automatically use the ip, or userAgent for gate evaluation as Statsig servers would, since there is no request from the client SDK specifying these values. If you want to use conditions like IP, or conditions which are inferred from the IP/UA like: Browser Name or Version, OS Name or Version, Country, you must manually set the ip and userAgent field on the user object when calling get_client_initialize_response.

Working with StableID

There is no auto-generated stableID for device based experimentation, since the server generates the initialize response without any information from the client SDK. If you wish to run a device based experiment while using the server to generate the initialize response, we recommend you:

  1. Create a customID in the Statsig console. See experimenting on custom IDs for more information.
  2. Generate an ID on the server, and set it in a cookie to be used on the client side as well.
  3. Set that ID as the customID on the StatsigUser object when generating the initialize response from the SDK.
  4. Get that ID from the cookie, and set it as the customID on the StatsigUser object when using the client SDK, so all event data and exposure checks tie back to the same user.

Alternatively, if you wish to use the stableID field rather than a custom ID, you still need to do step (2) above. Then:

  • Override the stableID in the client SDK by getting the value from the cookie and setting the overrideStableID parameter in StatsigOptions
  • Set the stableID field on the StatsigUser object in the customIDs map when generating the initialize response from the SDK

Local Overrides v1.12.0+

If you want to locally override gates/configs/experiments/layers, there are a set of override APIs as follows. Coupling this with StatsigOptions.localMode can be useful when writing unit tests.

# Adding gate overrides
Statsig.override_gate("a_gate_name", true)

# Adding config overrides
Statsig.override_config("a_config_name", {"key" => "value"})
  1. These only apply locally - they do not update definitions in the Statsig console or elsewhere.
  2. The local override API is not designed to be a full mock. They are only a convenient way to override the value of the gate/config/etc.

User Persistent Storage

A custom storage adapter that allows the SDK the persist values for users in active experiments. In otherwords, allowing you to run experiments with sticky bucketing. You can provide a persistent storage adapter via StatsigOptions.UserPersistentStorage.

You can read more about the concept here.

Storage Interface

You can write you own custom storage that implements the following interface:

class IUserPersistentStorage
def load(key)

def save(key, data) end

Example Implementation

class DummyPersistentStorageAdapter < Statsig::Interfaces::IUserPersistentStorage
attr_accessor :store

def initialize
@store = {}

def load(key)
return nil unless @store&.key?(key)


def save(key, data)
@store[key] = data


How do I run experiments for logged out users?

See the guide on device level experiments

How can I mock or override the SDK for testing?

Starting in v1.12.0+, the Ruby SDK supports localMode and overrides, see Local 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.

Can I generate the initialize response for a client SDK using the Ruby server SDK?

Yes. See Client Initialize Response.


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 # Hash of key:string value:string
attr_accessor :private_attributes # Hash of key:string value:string

@custom # Hash of key:string value:string

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 :bootstrap_values
attr_accessor :rules_updated_callback
attr_accessor :data_store
attr_accessor :idlist_threadpool_size
attr_accessor :disable_diagnostics_logging
attr_accessor :disable_sorbet_logging_handlers

def initialize(
environment: T.any(T::Hash[String, String], NilClass),
api_url_base: String,
rulesets_sync_interval: T.any(Float, Integer),
idlists_sync_interval: T.any(Float, Integer),
logging_interval_seconds: T.any(Float, Integer),
logging_max_buffer_size: Integer,
local_mode: T::Boolean,
bootstrap_values: T.any(String, NilClass),
rules_updated_callback: T.any(Method, Proc, NilClass),
data_store: T.any(Statsig::Interfaces::IDataStore, NilClass),
idlist_threadpool_size: Integer,
disable_diagnostics_logging: T::Boolean,
disable_sorbet_logging_handlers: T::Boolean)


module Statsig
module Interfaces
class IDataStore
def init

def get(key)

def set(key, value)

def shutdown