Example: Resilient HTTP RoundTripper for Rate-Limited APIs

[cinar]

Description: API integrations frequently encounter 429 Too Many Requests. This example will demonstrate how to create a custom http.RoundTripper that automatically pauses and resumes based on server-dictated Retry-After headers.

• Architecture & Implementation Requirements:

  • Setup: Create examples/http_ratelimit/main.go.
  • The Transport: Implement a custom struct ResilientTransport that wraps http.DefaultTransport.
  • Integration: Inside the RoundTrip method, wrap the downstream HTTP call in resile.Do.
  • Header Parsing: If the response is a 429, parse the Retry-After header (handling both integer seconds and HTTP date formats). Have the policy return a custom RateLimitError that implements Resile's RetryAfter() interface.

• Acceptance Criteria:

  • Provide a local mock HTTP server within the example that intentionally returns 429 responses to demonstrate the backoff dynamically.
  • Document how to inject this RoundTripper seamlessly into an existing http.Client.