Initializing a Client SDK

One of the first steps in using a Statsig client SDK is to call the asynchronous initialize() method in the SDK language of your choice. If you're looking for synchronous initialization or server side rendering, skip down to the bottom

General Flow

initialize will take an SDK key and StatsigUser object, as well as a set of options to parameterize the SDK. The sdk will then do a few things:

1. Check local storage for cached values. The SDK caches the previous evaluations locally so they are available on the next session without a successful network call
2. Create a cache a STATSIG_STABLE_ID for experimenting on stableID - e.g. for experimenting and stable evaluations across the logged out to logged in boundary, where there userID may go from undefined to known.
3. Set the SDK as initialized so checks won't throw - they will either return cached values or defaults.
4. Issue a network request to Statsig to get the latest values for all gates/experiments/configs/layers/autotunes for the given user. If the project definition does not change from the most recent cached values, this request may succeed without returning new data.
5. Resolve the asynchronous initialize call. If the request to the server failed, the SDK will have the cached values or return defaults for this session.

Synchronous Initialization

If asynchronous initialization is not an option for your performance requirements, you can initialize the SDK synchronously - throughout the docs, we refer to how you can accomplish this as "Server Side Rendering." The client SDK still needs to know the gate and experiment values for the given user at initialization time, but you can use a server SDK to generate those values, so when your first network roundtrip completes, you can initialize the statsig SDK synchronously rather than waiting for a network round trip to Statsig servers. The server SDK will take in a user object and use its local evaluation to generate the same response that the /initialize network call would generate.

This integration requires a client sdk and a server SDK, so it is a bit more setup, but it will give you the most performant way to integrate Statsig in your website. We currently only support this on the statsig-js or statsig-react sdks, but let us know in slack if you have another use case.

Schema of /initialize response

/** Specs for Dynamic Configs */
dynamic_configs: {
  [key: string]: {
    name: string;
    rule_id: string | null;
    value: { [key: string]: unknown };
    group?: string;
    secondary_exposures?: {
      gate: string,
      gateValue: string,
      ruleID: string,
    }[];
    undelegated_secondary_exposures?: {
      gate: string,
      gateValue: string,
      ruleID: string,
    }[];
    is_device_based?: boolean;
    is_user_in_experiment?: boolean;
    is_experiment_active?: boolean;
    explicit_parameters?: string[];
    is_in_layer?: boolean;
    allocated_experiment_name?: string;
  };
};
/** Specs for Feature Gates */
feature_gates: {
  [key: string]: {
    name: string;
    value: boolean;
    rule_id: string | null;
    secondary_exposures?: {
      gate: string,
      gateValue: string,
      ruleID: string,
    }[];
  };
};
/** Specs for Layer Configs */
layer_configs: {
  [key: string]: {
    name: string;
    rule_id: string | null;
    value: { [key: string]: unknown };
    group?: string;
    secondary_exposures?: {
      gate: string,
      gateValue: string,
      ruleID: string,
    }[];
    undelegated_secondary_exposures?: {
      gate: string,
      gateValue: string,
      ruleID: string,
    }[];
    is_device_based?: boolean;
    is_user_in_experiment?: boolean;
    is_experiment_active?: boolean;
    explicit_parameters?: string[];
    is_in_layer?: boolean;
    allocated_experiment_name?: string;
  };
};
/** Whether the response contains updates from the sinceTime */
has_updates: boolean;
/** Name of the service that generated the response */
generator: string;
/** Timestamp of response */
time: number;
/** Timestamp of company's last config update time */
company_lcut: number;
/** The user keys evaluated */
evaluated_keys: {
  userID?: string;
  stableID?: string;
  customIDs?: Record<string, string>;
};
/** The hashing algorithm used */
hash_used: string;