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Using SpecsDataAdapter

The StatsigSpecsDataAdapter is the default SpecsDataAdapter used by a StatsigOnDeviceEvalClient instance.

It handles fetching and caching values from Statsig's servers. If required, you can create your own custom SpecsDataAdapter and provide it to the Statsig client via StatsigOptions.dataAdapter.

Overview​

Synchronous Behavior (Cache)​

When calling StatsigOnDeviceEvalClient.initializeSync, the StatsigSpecsDataAdapter will load values from Cache and provide them to the client. The client will also call refresh in the background via StatsigSpecsDataAdapter.getDataAsync, leading to values lagging until the next time initializeSync.

In practice, this means that for the very first session, there will be no values, and not until the next session will the cache have values.

Asynchronous Behavior (Network)​

When calling StatsigOnDeviceEvalClient.initializeAsync, the StatsigSpecsDataAdapter will load values from Cache and provide them to the client. The client will then block on a call to StatsigSpecsDataAdapter.getDataAsync, allowing the ability to await the latest values from Statsig.

If you want the latest values, but do not want to await the asynchronous call, you may call initializeAsync and simply .catch the promise. Note that this could lead to values changing mid-session as newer values arrive from the network.

Advanced Usage​

Getting the Data Adapter​

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Bootstrapping​

Bootstrapping allows you to provide the required data without a network call. This can be useful if you do not wish to make network calls during startup.

If you are building a mobile app and want to bundle values with your application. Then you can load the values from a local file at startup and provide them to the data adapter.

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Note: You can get a copy of your current specs data by visiting: https://api.statsigcdn.com/v1/download_config_specs/client-{YOUR_SDK_KEY}.json

Custom Implementation​

If you would like to customize when and how data is fetched, as well as where it is stored, you can create your own class the conforms to the SpecsDataAdapter type.

The SpecsDataAdapter type outlines the following functions:

  • attach - Called when the SpecsDataAdapter is passed into a StatsigOnDeviceEvalClient via StatsigOptions. This allows the SpecsDataAdapter to use the same SDK Key and StatsigOptions as the StatsigOnDeviceEvalClient instance.

    • attach: (sdkKey: string, options: StatsigOptionsCommon | null) => void

  • getDataSync - Synchronously get evaluation data for the given user. Called during initializeSync. It is also called during async update operations before StatsigDataAdapter.getDataAsync is called.

    • getDataSync: () => DataAdapterResult | null;

  • getDataAsync - Asynchronously get evaluation data for the given user. Called during initializeAsync.

    • getDataAsync: (current: DataAdapterResult | null) => Promise<DataAdapterResult | null>;

  • prefetchData - Manually trigger a fetch for new specs data.

    • prefetchData: () => Promise<void>;

  • setData - Manually set specs data.

    • setData: (data: string) => Promise<void>;