zai-proxy/notes/bf-244.md

BF-244: Unit Tests for 429 Retry Logic

Summary

Verified that comprehensive 429 retry unit tests already exist in proxy/retry_test.go. All tests pass with race detector (go test ./proxy/ -run Test429 -race).

Test Coverage

429 with Retry-After Header Tests

1. Test429WithRetryAfterMetricVerification (lines 1113-1185)

   • Verifies 429 with Retry-After header honors the delay before retry
   • Returns success after retry
   • Verifies exactly 2 upstream calls (initial + retry)
   • Verifies zai_proxy_retry_attempts_total{reason="429"} incremented exactly once
   • Verifies duration reflects Retry-After delay

2. TestIntegration429WithRetryAfter (lines 1482-1544)

   • Integration test using real ProxyHandler
   • Verifies multiple 429s before success
   • Verifies upstream call count matches retries + 1
   • Verifies total duration reflects cumulative Retry-After delays

429 without Retry-After Header Tests

3. Test429WithoutRetryAfterMetricVerification (lines 1192-1254)

   • Verifies 429 without Retry-After uses exponential backoff
   • Returns 429 to client after MAX_RETRIES exhausted
   • Verifies exactly MAX_RETRIES+1 upstream calls (initial + retries)
   • Verifies zai_proxy_retry_attempts_total{reason="429"} incremented MAX_RETRIES times
   • Verifies duration reflects exponential backoff (1s + 2s for maxRetries=2)

4. TestIntegration429NoHeader (lines 1547-1590)

   • Integration test using real ProxyHandler
   • Verifies exponential backoff behavior
   • Verifies 429 is surfaced after retries exhausted
   • Verifies upstream call count

Additional 429 Tests

5. Test429MultipleRetriesMetricVerification (lines 1260-1328)

   • Tests multiple 429s before success
   • Verifies metric increments once per 429 response
   • Verifies upstream call count matches failure + success attempts

6. Test429MetricLabelVerification (lines 1331-1370)

   • Verifies retry metric uses correct reason="429" label
   • Verifies other reason labels are not incremented
   • Ensures metric label integrity

7. Test429ConcurrentMetricVerification (lines 1374-1450)

   • Tests concurrent 429 responses are tracked correctly
   • Verifies metric increments count concurrent retries
   • Verifies thread-safe metric handling

Acceptance Criteria Met

✅ New tests in proxy/retry_test.go covering 429+Retry-After and 429 without Retry-After ✅ Upstream call count assertions for each case ✅ Metric assertions for retry attempts (zai_proxy_retry_attempts_total) ✅ go test ./proxy/ -run Test429 passes with -race

Test Results

All 429 tests pass successfully:

=== RUN   Test429WithRetryAfterThenSuccess
--- PASS: Test429WithRetryAfterThenSuccess (0.00s)
=== RUN   Test429WithoutRetryAfter
--- PASS: Test429WithoutRetryAfter (0.00s)
=== RUN   Test429WithRetryAfterMetricVerification
--- PASS: Test429WithRetryAfterMetricVerification (2.00s)
=== RUN   Test429WithoutRetryAfterMetricVerification
--- PASS: Test429WithoutRetryAfterMetricVerification (3.00s)
=== RUN   Test429MultipleRetriesMetricVerification
--- PASS: Test429MultipleRetriesMetricVerification (5.01s)
=== RUN   Test429MetricLabelVerification
--- PASS: Test429MetricLabelVerification (1.00s)
=== RUN   Test429ConcurrentMetricVerification
--- PASS: Test429ConcurrentMetricVerification (1.00s)
PASS

Test file location: /home/coding/zai-proxy/proxy/retry_test.go

Uses test infrastructure from: bf-3zp (mock upstream server, metrics verification)