tas-client

Purpose

This package is intended to be used as an endpoint client to query, refetch, and cache data from the Experimentation service (or any given endpoint). The endpoint result must follow the required structure for experimentation data.

Development

Building

• npm run compile - Compile TypeScript to JavaScript
• npm run bundle - Bundle the package into a single file (output: out/bundle/tas-client.js)
• npm run watch - Watch mode for TypeScript compilation
• npm test - Run tests

Usage

First, your client should implement an IExperimentationFilterProvider, IExperimentationTelemetry, and IKeyValueStorage.

Next, they can be used in the TASClient constructor:

const tasClient = new TASClient({
			filterProviders: [filterProvider],
			telemetry: telemetry,
			storageKey: storageKey,
			keyValueStorage: keyValueStorage,
			assignmentContextTelemetryPropertyName: '<assignmentContextTelemetryPropertyName>',
			telemetryEventName: '<telemetryEventName>',
			endpoint: '<tas-endpoint>',
			refetchInterval: refetchInterval,
		});

The client provides a variety of functions, but the most basic is getTreatmentVariable(configId: string, name: string). Once you have an instance of IExperimentationService you can call getTreatmentVariable to get the value of a treatment variable.

NOTE: If you haven't awaited the IExperimentationService's initializePromise, you need to use getTreatmentVariableAsync.

0.4.3

Custom transport (fetch)

By default the client issues requests with its built-in HTTP client. To route requests through your own networking stack (for example to add proxy support, retries, or a custom user-agent), provide a fetch function in the config. It is used for both the legacy endpoint (GET) and the optional assignmentsEndpoint (POST):

const tasClient = new TASClient({
    // ...existing options...
    endpoint: '<tas-endpoint>',
    assignmentsEndpoint: '<assignments-endpoint>', // optional
    extensionName: '<caller-name>',                // optional; attached to `tas-call` telemetry
    fetch: async (url, init) => {
        // init.method is 'GET' (legacy) or 'POST' (assignments); init.body is set for POST.
        const res = await myHttp(url, { method: init.method, headers: init.headers, body: init.body });
        return { status: res.status, json: () => res.json() };
    },
});

A per-endpoint assignmentsFetch still overrides fetch for the assignments request. The deprecated AssignmentsFetchFn / IAssignmentsFetchResponse types remain as aliases of FetchFn / IFetchResponse.

Telemetry: tas-call

Each TAS call emits a uniform tas-call event so callers can confirm calls are being made and are succeeding:

| Property | Description | | --- | --- | | callType | legacy or assignments | | outcome | Success, ServerError, NoResponse, or GenericError | | extensionName | The caller name provided via config | | assignmentContext | The assignment context returned by that call |