Do not treat missing num values as parse errors (#228)

features/issues.feature

@@ -34,4 +34,14 @@ Feature: Various issues reported in the bug tracker remain solved
       www.example.com 10.0.0.2 - - [27/Oct/2021:06:00:15 +0200] "GET /websocket HTTP/1.1" 200 552 "-" "AnotherUserAgent" 0.000 "1.000, 0.250, 2.000, 0.750" . TLSv1.3/TLS_AES_256_GCM_SHA384 1234567890 www.example.com
       www.example.com 10.0.0.3 - - [27/Oct/2021:06:00:15 +0200] "GET /websocket HTTP/1.1" 200 150 "-" "SomeUserAgentString" 0.001 "1.000, 0.250, 2.000, 0.750" . TLSv1.3/TLS_AES_256_GCM_SHA384 1234567890 www.example.com
       """
-    Then the exporter should report value 12 for metric test_http_upstream_time_seconds_sum{method="GET",status="200"}
+    Then the exporter should report value 12 for metric test_http_upstream_time_seconds_sum{method="GET",status="200"}
+
+  Scenario: Issue 224: Missing float values
+    Given a running exporter listening with configuration file "test-config-issue217.yaml"
+    When the following HTTP request is logged to "access.log"
+      """
+      www.example.com 10.0.0.1 - - [27/Oct/2021:06:00:14 +0200] "GET /websocket HTTP/1.1" 200 552 "-" "SomeUserAgentString" 0.000 "1.000, -, 2.000" . TLSv1.3/TLS_AES_256_GCM_SHA384 1234567890 www.example.com
+      www.example.com 10.0.0.2 - - [27/Oct/2021:06:00:15 +0200] "GET /websocket HTTP/1.1" 200 552 "-" "AnotherUserAgent" - "1.000" . TLSv1.3/TLS_AES_256_GCM_SHA384 1234567890 www.example.com
+      """
+    Then the exporter should report value 0 for metric test_parse_errors_total
+    Then the exporter should report value 4 for metric test_http_upstream_time_seconds_sum{method="GET",status="200"}

main.go

@@ -446,6 +446,10 @@ func floatFromFieldsMulti(fields map[string]string, name string) (float64, bool,
 	for _, v := range strings.Split(val, ",") {
 		v = strings.TrimSpace(v)
 
+		if v == "-" {
+			continue
+		}
+
 		f, err := strconv.ParseFloat(v, 64)
 		if err != nil {
 			return 0, false, fmt.Errorf("value '%s' could not be parsed into float", val)
@@ -463,6 +467,10 @@ func floatFromFields(fields map[string]string, name string) (float64, bool, erro
 		return 0, false, nil
 	}
 
+	if val == "-" {
+		return 0, false, nil
+	}
+
 	f, err := strconv.ParseFloat(val, 64)
 	if err != nil {
 		return 0, false, fmt.Errorf("value '%s' could not be parsed into float", val)