Merge pull request #2176 from Alix-007/fix/issue-2135-retry-after

fix(utils): honor Retry-After for 429 retries
2026-06-12 18:08:54 +00:00 · 2026-03-30 16:27:46 +02:00
parent 187b2c2185 711685192c
commit 7b3f47128f
2 changed files with 216 additions and 2 deletions
@@ -4,12 +4,16 @@ import (
 	"context"
 	"fmt"
 	"net/http"
+	"strconv"
 	"time"
 )

 const maxRetries = 3

-var retryDelayUnit = time.Second
+var (
+	retryDelayUnit        = time.Second
+	maxRetrySleepDuration = 1 * time.Minute
+)

 func shouldRetry(statusCode int) bool {
 	return statusCode == http.StatusTooManyRequests ||
@@ -36,7 +40,7 @@ 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 +51,57 @@ 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 clampRetryDelay(fallback)
+	}
+
+	retryAfter := resp.Header.Get("Retry-After")
+	if retryAfter == "" {
+		return clampRetryDelay(fallback)
+	}
+
+	if delay, ok := numericRetryAfterDelay(retryAfter); ok {
+		return delay
+	}
+
+	if when, err := http.ParseTime(retryAfter); err == nil {
+		delay := time.Until(when)
+		if serverDate, err := http.ParseTime(resp.Header.Get("Date")); err == nil {
+			delay = when.Sub(serverDate)
+		}
+		if delay < 0 {
+			return 0
+		}
+		return clampRetryDelay(delay)
+	}
+
+	return clampRetryDelay(fallback)
+}
+
+func numericRetryAfterDelay(retryAfter string) (time.Duration, bool) {
+	seconds, err := strconv.ParseInt(retryAfter, 10, 64)
+	if err != nil || seconds < 0 {
+		return 0, false
+	}
+	maxSeconds := int64(maxRetrySleepDuration / time.Second)
+	if seconds > maxSeconds {
+		return maxRetrySleepDuration, true
+	}
+	return clampRetryDelay(time.Duration(seconds) * time.Second), true
+}
+
+func clampRetryDelay(delay time.Duration) time.Duration {
+	if delay <= 0 {
+		return 0
+	}
+	if delay > maxRetrySleepDuration {
+		return maxRetrySleepDuration
+	}
+	return delay
+}
+
 func sleepWithCtx(ctx context.Context, d time.Duration) error {
 	timer := time.NewTimer(d)
 	defer timer.Stop()
@@ -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
@@ -204,3 +279,87 @@ func TestDoRequestWithRetry_Delay(t *testing.T) {

 	assert.GreaterOrEqual(t, delays[2], time.Millisecond)
 }
+
+func TestRetryDelayForAttempt_DateRetryAfterUsesResponseDateHeader(t *testing.T) {
+	maxRetrySleepDuration = time.Minute
+	t.Cleanup(func() { maxRetrySleepDuration = time.Minute })
+
+	serverDate := time.Date(2000, 1, 2, 15, 4, 5, 0, time.UTC)
+	retryAfterAt := serverDate.Add(10 * time.Second)
+	resp := &http.Response{
+		StatusCode: http.StatusTooManyRequests,
+		Header: http.Header{
+			"Retry-After": []string{retryAfterAt.Format(http.TimeFormat)},
+			"Date":        []string{serverDate.Format(http.TimeFormat)},
+		},
+	}
+
+	assert.Equal(t, 10*time.Second, retryDelayForAttempt(resp, 0))
+}
+
+func TestRetryDelayForAttempt_DateRetryAfterInvalidOrMissingDateFallsBackSafely(t *testing.T) {
+	maxRetrySleepDuration = 30 * time.Second
+	t.Cleanup(func() { maxRetrySleepDuration = time.Minute })
+
+	retryAfterAt := time.Now().UTC().Add(3 * time.Second).Format(http.TimeFormat)
+	testcases := []struct {
+		name   string
+		header http.Header
+	}{
+		{
+			name: "invalid-date-header",
+			header: http.Header{
+				"Retry-After": []string{retryAfterAt},
+				"Date":        []string{"invalid-date"},
+			},
+		},
+		{
+			name: "missing-date-header",
+			header: http.Header{
+				"Retry-After": []string{retryAfterAt},
+			},
+		},
+	}
+
+	for _, tc := range testcases {
+		t.Run(tc.name, func(t *testing.T) {
+			resp := &http.Response{
+				StatusCode: http.StatusTooManyRequests,
+				Header:     tc.header,
+			}
+
+			delay := retryDelayForAttempt(resp, 0)
+			assert.Greater(t, delay, time.Duration(0))
+			assert.GreaterOrEqual(t, delay, 1500*time.Millisecond)
+			assert.LessOrEqual(t, delay, 5*time.Second)
+		})
+	}
+}
+
+func TestRetryDelayForAttempt_RetryAfterIsCapped(t *testing.T) {
+	maxRetrySleepDuration = 2 * time.Second
+	t.Cleanup(func() { maxRetrySleepDuration = time.Minute })
+
+	resp := &http.Response{
+		StatusCode: http.StatusTooManyRequests,
+		Header: http.Header{
+			"Retry-After": []string{"999999"},
+		},
+	}
+
+	assert.Equal(t, 2*time.Second, retryDelayForAttempt(resp, 0))
+}
+
+func TestRetryDelayForAttempt_RetryAfterNumericOverflowStillCaps(t *testing.T) {
+	maxRetrySleepDuration = 2 * time.Second
+	t.Cleanup(func() { maxRetrySleepDuration = time.Minute })
+
+	resp := &http.Response{
+		StatusCode: http.StatusTooManyRequests,
+		Header: http.Header{
+			"Retry-After": []string{"9223372036854775807"},
+		},
+	}
+
+	assert.Equal(t, 2*time.Second, retryDelayForAttempt(resp, 0))
+}