Address Okta input issue #18530 (#18534)

* Add check for time because time.Until does not correctly handle a time that is earlier than time.Now().

* Update getRateLimit to handle a rate limit time is earlier than now.

* Add some additional safe guard to check Ticker

* Add descriptions for getRateLimit function and test functions.

* Update CHANGELOG.next.asciidoc

CHANGELOG.next.asciidoc

@@ -135,6 +135,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Improve cisco asa and ftd pipelines' failure handler to avoid mapping temporary fields. {issue}18391[18391] {pull}18392[18392]
 - Fix PANW module wrong mappings for bytes and packets counters. {issue}18522[18522] {pull}18525[18525]
 - Fixed ingestion of some Cisco ASA and FTD messages when a hostname was used instead of an IP for NAT fields. {issue}14034[14034] {pull}18376[18376]
+- Fix a rate limit related issue in httpjson input for Okta module. {issue}18530[18530] {pull}18534[18534]
 
 *Heartbeat*
 

x-pack/filebeat/input/httpjson/httpjson_test.go

@@ -334,6 +334,7 @@ func TestCreateRequestInfoFromBody(t *testing.T) {
 	}
 }
 
+// Test getRateLimit function with a remaining quota, expect to receive 0, nil.
 func TestGetRateLimitCase1(t *testing.T) {
 	header := make(http.Header)
 	header.Add("X-Rate-Limit-Limit", "120")
@@ -350,6 +351,7 @@ func TestGetRateLimitCase1(t *testing.T) {
 	}
 }
 
+// Test getRateLimit function with a past time, expect to receive 0, nil.
 func TestGetRateLimitCase2(t *testing.T) {
 	header := make(http.Header)
 	header.Add("X-Rate-Limit-Limit", "10")
@@ -361,7 +363,25 @@ func TestGetRateLimitCase2(t *testing.T) {
 		Remaining: "X-Rate-Limit-Remaining",
 	}
 	epoch, err := getRateLimit(header, rateLimit)
-	if err != nil || epoch != 1581658643 {
+	if err != nil || epoch != 0 {
+		t.Fatal("Failed to test getRateLimit.")
+	}
+}
+
+// Test getRateLimit function with a time yet to come, expect to receive <reset-value>, nil.
+func TestGetRateLimitCase3(t *testing.T) {
+	epoch := time.Now().Unix() + 100
+	header := make(http.Header)
+	header.Add("X-Rate-Limit-Limit", "10")
+	header.Add("X-Rate-Limit-Remaining", "0")
+	header.Add("X-Rate-Limit-Reset", strconv.FormatInt(epoch, 10))
+	rateLimit := &RateLimit{
+		Limit:     "X-Rate-Limit-Limit",
+		Reset:     "X-Rate-Limit-Reset",
+		Remaining: "X-Rate-Limit-Remaining",
+	}
+	epoch2, err := getRateLimit(header, rateLimit)
+	if err != nil || epoch2 != epoch {
 		t.Fatal("Failed to test getRateLimit.")
 	}
 }

x-pack/filebeat/input/httpjson/input.go

@@ -201,7 +201,10 @@ func getNextLinkFromHeader(header http.Header, fieldName string, re *regexp.Rege
 	return "", nil
 }
 
-// getRateLimit get the rate limit value if specified in the HTTP Header of the response
+// getRateLimit get the rate limit value if specified in the HTTP Header of the response,
+// and returns an init64 value in seconds since unix epoch for rate limit reset time.
+// When there is a remaining rate limit quota, or when the rate limit reset time has expired, it
+// returns 0 for the epoch value.
 func getRateLimit(header http.Header, rateLimit *RateLimit) (int64, error) {
 	if rateLimit != nil {
 		if rateLimit.Remaining != "" {
@@ -222,6 +225,9 @@ func getRateLimit(header http.Header, rateLimit *RateLimit) (int64, error) {
 				if err != nil {
 					return 0, errors.Wrapf(err, "failed to parse rate-limit reset value")
 				}
+				if time.Unix(epoch, 0).Sub(time.Now()) <= 0 {
+					return 0, nil
+				}
 				return epoch, nil
 			}
 		}
@@ -235,12 +241,14 @@ func (in *HttpjsonInput) applyRateLimit(ctx context.Context, header http.Header,
 	if err != nil {
 		return err
 	}
-	if epoch == 0 {
+	t := time.Unix(epoch, 0)
+	w := time.Until(t)
+	if epoch == 0 || w <= 0 {
+		in.log.Debugf("Rate Limit: No need to apply rate limit.")
 		return nil
 	}
-	t := time.Unix(epoch, 0)
 	in.log.Debugf("Rate Limit: Wait until %v for the rate limit to reset.", t)
-	ticker := time.NewTicker(time.Until(t))
+	ticker := time.NewTicker(w)
 	defer ticker.Stop()
 	select {
 	case <-ctx.Done():