HttpClient 429 + Retry-After package

What you get (4 files):

📄 RetryAfterDelegatingHandler.cs: Backpressure-aware HttpClient handler

• Correct parsing: Retry-After seconds and HTTP date
• Boundaries: max delay cap and optional jitter
• Integration hint: register with HttpClientFactory or wrap in your own client

✅ 429-retry-after-runbook.md: Operator runbook for sustained throttling

• Confirm source: which dependency is actually returning 429
• Contain: cap concurrency, shed low priority, slow down safely
• Recover: validate reduction in retry amplification

📊 retry-after-logging-fields.md: Field list for queryable incident logs

• Decision fields: wait, reason, attempt, budget, route
• Correlation: correlate retries to request and job IDs
• Queries: how to prove you honored backpressure

📋 README.md: Setup + guardrails

• Where to put the handler
• Defaults to start with
• What not to retry (unsafe side effects)

Quick reference (inline preview):

Decision rule for 429
- If Retry-After present and within budget: delay-and-retry (bounded)
- If Retry-After missing: short bounded backoff + escalate if sustained
- If side effect is not idempotent: fail-fast and surface an actionable error