Skip to main content
📜 WAYPOINT LESSON

Checkpoint — The Public API Client

⭐⭐ intermediate⏳ 25 min read📍 Lesson 128 of 265

Compose the pieces: typed client over a stub handler, mapped outcomes, retries with capped backoff, cancellation honored.

The gate (mini-build)

A resilient API client — the shape from the lesson, assembled:

  1. ApiClient(HttpClient http) — injected client (Module 11 discipline).
  2. GetUserAsync(int id, CancellationToken ct) → GET /users/{id}. Outcomes: "user:<name>" on 200, "notfound" on 404, "failed" on any other status.
  3. GetUserWithRetryAsync(int id, int maxAttempts, CancellationToken ct) — same contract, but 5xx attempts are retried with the harness's recorded delays (non-decreasing, capped at 50 ms); 404 is NOT retried.
  4. Cancellation wins: a pre-cancelled token throws OperationCanceledException before any request.

Provided: CjStubHandler (records requests, replays scripted responses, records fake delays).