fix(github): utilize RateLimitError.Rate

pkg/sources/github/github.go

@@ -829,16 +829,22 @@ func (s *Source) scan(ctx context.Context, installationClient *github.Client, ch
 // This will likely only be exhausted if many users/orgs are scanned without auth
 func (s *Source) handleRateLimit(errIn error, res *github.Response) bool {
 	var (
+		now        = time.Now()
 		knownWait  = true
 		remaining  = 0
 		retryAfter time.Duration
 	)
 
 	// GitHub has both primary (RateLimit) and secondary (AbuseRateLimit) errors.
-	var rateLimit *github.RateLimitError
-	var abuseLimit *github.AbuseRateLimitError
+	var (
+		rateLimit  *github.RateLimitError
+		abuseLimit *github.AbuseRateLimitError
+	)
 	if errors.As(errIn, &rateLimit) {
-		// Do nothing
+		rate := rateLimit.Rate
+		if rate.Remaining == 0 {
+			retryAfter = rate.Reset.Sub(now)
+		}
 	} else if errors.As(errIn, &abuseLimit) {
 		retryAfter = abuseLimit.GetRetryAfter()
 	} else {
@@ -850,25 +856,33 @@ func (s *Source) handleRateLimit(errIn error, res *github.Response) bool {
 	// https://docs.github.com/en/rest/overview/resources-in-the-rest-api#exceeding-the-rate-limit
 	if retryAfter <= 0 && res != nil {
 		var err error
-		remaining, err = strconv.Atoi(res.Header.Get("x-ratelimit-remaining"))
-		if err != nil {
-			knownWait = false
+
+		remainingHeader := res.Header.Get("x-ratelimit-remaining")
+		if remainingHeader != "" {
+			if remaining, err = strconv.Atoi(remainingHeader); err != nil {
+				knownWait = false
+			}
 		}
 
-		resetTime, err := strconv.Atoi(res.Header.Get("x-ratelimit-reset"))
-		if err != nil || resetTime == 0 {
-			knownWait = false
-		} else if resetTime > 0 {
-			retryAfter = time.Duration(int64(resetTime)-time.Now().Unix()) * time.Second
+		resetHeader := res.Header.Get("x-ratelimit-reset")
+		if resetHeader != "" {
+			resetTime, err := strconv.Atoi(resetHeader)
+			if err != nil || resetTime == 0 {
+				knownWait = false
+			} else if resetTime > 0 {
+				retryAfter = time.Duration(int64(resetTime)-now.Unix()) * time.Second
+			}
 		}
 	}
 
-	resumeTime := time.Now().Add(retryAfter).String()
+	var resumeTime string
 	if knownWait && remaining == 0 && retryAfter > 0 {
+		resumeTime = now.Add(retryAfter).String()
 		s.log.V(2).Info("rate limited", "retry_after", retryAfter.String(), "resume_time", resumeTime)
 	} else {
-		// TODO: Use exponential backoff instead of static retry time.
 		retryAfter = time.Minute * 5
+		resumeTime = now.Add(retryAfter).String()
+		// TODO: Use exponential backoff instead of static retry time.
 		s.log.V(2).Error(errIn, "unexpected rate limit error", "retry_after", retryAfter.String(), "resume_time", resumeTime)
 	}
 	time.Sleep(retryAfter)