Return an error if no valid patterns. (#2753)

plugins/inputs/logparser/grok/grok.go

@@ -118,11 +118,18 @@ func (p *Parser) Compile() error {
 
 	// Give Patterns fake names so that they can be treated as named
 	// "custom patterns"
-	p.namedPatterns = make([]string, len(p.Patterns))
+	p.namedPatterns = make([]string, 0, len(p.Patterns))
 	for i, pattern := range p.Patterns {
+		if pattern == "" {
+			continue
+		}
 		name := fmt.Sprintf("GROK_INTERNAL_PATTERN_%d", i)
 		p.CustomPatterns += "\n" + name + " " + pattern + "\n"
-		p.namedPatterns[i] = "%{" + name + "}"
+		p.namedPatterns = append(p.namedPatterns, "%{"+name+"}")
+	}
+
+	if len(p.namedPatterns) == 0 {
+		return fmt.Errorf("pattern required")
 	}
 
 	// Combine user-supplied CustomPatterns with DEFAULT_PATTERNS and parse

plugins/inputs/logparser/logparser.go

@@ -117,16 +117,11 @@ func (l *LogParserPlugin) Start(acc telegraf.Accumulator) error {
 	}
 
 	// compile log parser patterns:
-	var haveError bool
 	for _, parser := range l.parsers {
 		if err := parser.Compile(); err != nil {
-			acc.AddError(err)
+			return err
-			haveError = true
 		}
 	}
-	if haveError {
-		return nil
-	}
 
 	l.wg.Add(1)
 	go l.parser()

plugins/inputs/logparser/logparser_test.go

@@ -38,12 +38,8 @@ func TestGrokParseLogFilesNonExistPattern(t *testing.T) {
 	}
 
 	acc := testutil.Accumulator{}
-	logparser.Start(&acc)
+	err := logparser.Start(&acc)
-	if assert.NotEmpty(t, acc.Errors) {
+	assert.Error(t, err)
-		assert.Error(t, acc.Errors[0])
-	}
-
-	logparser.Stop()
 }
 
 func TestGrokParseLogFiles(t *testing.T) {