Fix for divide by zero error by defaulting to current year if no year is given in timestamp

plugins/inputs/logparser/grok/grok.go

@@ -337,6 +337,9 @@ func (p *Parser) ParseLine(line string) (telegraf.Metric, error) {
 		default:
 			ts, err := time.ParseInLocation(t, v, p.loc)
 			if err == nil {
+				if ts.Year() == 0 {
+					ts = ts.AddDate(timestamp.Year(), 0, 0)
+				}
 				timestamp = ts
 			} else {
 				log.Printf("E! Error parsing %s to time layout [%s]: %s", v, t, err)
@@ -466,7 +469,6 @@ func (t *tsModder) tsMod(ts time.Time) time.Time {
 		t.rollover = 0
 		return ts
 	}
-
 	if ts.Equal(t.last) {
 		t.dupe = ts
 	}

plugins/inputs/logparser/grok/grok_test.go

@@ -982,3 +982,19 @@ func TestSyslogTimestampParser(t *testing.T) {
 	require.NotNil(t, m)
 	require.Equal(t, 2018, m.Time().Year())
 }
+
+func TestFailDivideByZeroError(t *testing.T) {
+	p := &Parser{
+		Patterns: []string{`%{APPLE_SYSLOG_TIME_SHORT:timestamp:ts-"Jan 2 15:04:05"} %{HOSTNAME} %{APP_NAME:app_name}\[%{NUMBER:pid:int}\]%{GREEDYDATA:message}`},
+		CustomPatterns: `
+		APPLE_SYSLOG_TIME_SHORT %{MONTH} +%{MONTHDAY} %{TIME}
+		APP_NAME [a-zA-Z0-9\.]+
+		`,
+	}
+	require.NoError(t, p.Compile())
+	m, err := p.ParseLine("Nov  6 13:57:03 rsavage iTunes[6504]: info> Scale factor of main display = 2.0")
+	m, err = p.ParseLine("Nov  6 13:57:03 rsavage iTunes[6504]: objc[6504]: Class AMSupportURLConnectionDelegate is implemented in both /System/Library/PrivateFrameworks/EmbeddedOSInstall.framework/Versions/A/EmbeddedOSInstall (0x7fffa594e748) and /System/Library/PrivateFrameworks/MobileDevice.framework/MobileDevice (0x107e67008). One of the two will be used. Which one is undefined.")
+	require.NoError(t, err)
+	require.NotNil(t, m)
+	require.Equal(t, 2018, m.Time().Year())
+}