fix(utils): honor Retry-After for 429 retries

pkg/utils/http_retry.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"net/http"
+	"strconv"
 	"time"
 )
 
@@ -36,7 +37,7 @@ func DoRequestWithRetry(client *http.Client, req *http.Request) (*http.Response,
 		}
 
 		if i < maxRetries-1 {
-			if err = sleepWithCtx(req.Context(), retryDelayUnit*time.Duration(i+1)); err != nil {
+			if err = sleepWithCtx(req.Context(), retryDelayForAttempt(resp, i)); err != nil {
 				if resp != nil {
 					resp.Body.Close()
 				}
@@ -47,6 +48,32 @@ func DoRequestWithRetry(client *http.Client, req *http.Request) (*http.Response,
 	return resp, err
 }
 
+func retryDelayForAttempt(resp *http.Response, attempt int) time.Duration {
+	fallback := retryDelayUnit * time.Duration(attempt+1)
+	if resp == nil || resp.StatusCode != http.StatusTooManyRequests {
+		return fallback
+	}
+
+	retryAfter := resp.Header.Get("Retry-After")
+	if retryAfter == "" {
+		return fallback
+	}
+
+	if seconds, err := strconv.Atoi(retryAfter); err == nil && seconds >= 0 {
+		return time.Duration(seconds) * time.Second
+	}
+
+	if when, err := http.ParseTime(retryAfter); err == nil {
+		delay := time.Until(when)
+		if delay < 0 {
+			return 0
+		}
+		return delay
+	}
+
+	return fallback
+}
+
 func sleepWithCtx(ctx context.Context, d time.Duration) error {
 	timer := time.NewTimer(d)
 	defer timer.Stop()

pkg/utils/http_retry_test.go

@@ -80,6 +80,81 @@ func TestDoRequestWithRetry(t *testing.T) {
 	}
 }
 
+func TestDoRequestWithRetry_RetryAfter429Honored(t *testing.T) {
+	retryDelayUnit = 10 * time.Millisecond
+	t.Cleanup(func() { retryDelayUnit = time.Second })
+
+	attempts := 0
+	var firstAttemptAt time.Time
+	var secondAttemptAt time.Time
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		attempts++
+		if attempts == 1 {
+			firstAttemptAt = time.Now()
+			w.Header().Set("Retry-After", "1")
+			w.WriteHeader(http.StatusTooManyRequests)
+			return
+		}
+		if attempts == 2 {
+			secondAttemptAt = time.Now()
+		}
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer server.Close()
+
+	client := &http.Client{Timeout: 5 * time.Second}
+	req, err := http.NewRequest(http.MethodGet, server.URL, nil)
+	require.NoError(t, err)
+
+	resp, err := DoRequestWithRetry(client, req)
+	require.NoError(t, err)
+	require.NotNil(t, resp)
+	assert.Equal(t, http.StatusOK, resp.StatusCode)
+	resp.Body.Close()
+	require.Equal(t, 2, attempts)
+
+	assert.GreaterOrEqual(t, secondAttemptAt.Sub(firstAttemptAt), 900*time.Millisecond)
+}
+
+func TestDoRequestWithRetry_RetryAfter429InvalidFallsBack(t *testing.T) {
+	retryDelayUnit = 50 * time.Millisecond
+	t.Cleanup(func() { retryDelayUnit = time.Second })
+
+	attempts := 0
+	var firstAttemptAt time.Time
+	var secondAttemptAt time.Time
+
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		attempts++
+		if attempts == 1 {
+			firstAttemptAt = time.Now()
+			w.Header().Set("Retry-After", "invalid")
+			w.WriteHeader(http.StatusTooManyRequests)
+			return
+		}
+		if attempts == 2 {
+			secondAttemptAt = time.Now()
+		}
+		w.WriteHeader(http.StatusOK)
+	}))
+	defer server.Close()
+
+	client := &http.Client{Timeout: 5 * time.Second}
+	req, err := http.NewRequest(http.MethodGet, server.URL, nil)
+	require.NoError(t, err)
+
+	resp, err := DoRequestWithRetry(client, req)
+	require.NoError(t, err)
+	require.NotNil(t, resp)
+	assert.Equal(t, http.StatusOK, resp.StatusCode)
+	resp.Body.Close()
+	require.Equal(t, 2, attempts)
+
+	assert.GreaterOrEqual(t, secondAttemptAt.Sub(firstAttemptAt), 45*time.Millisecond)
+	assert.Less(t, secondAttemptAt.Sub(firstAttemptAt), 500*time.Millisecond)
+}
+
 func TestDoRequestWithRetry_ContextCancel(t *testing.T) {
 	// Use a long retry delay so cancellation always hits during sleepWithCtx.
 	retryDelayUnit = 10 * time.Second