Add max_message_len in kafka_consumer input (#2636)

plugins/inputs/kafka_consumer/kafka_consumer_test.go

@@ -1,6 +1,7 @@
 package kafka_consumer
 
 import (
+	"strings"
 	"testing"
 
 	"github.com/influxdata/telegraf/plugins/parsers"
@@ -62,6 +63,23 @@ func TestRunParserInvalidMsg(t *testing.T) {
 	assert.Equal(t, acc.NFields(), 0)
 }
 
+// Test that overlong messages are dropped
+func TestDropOverlongMsg(t *testing.T) {
+	const maxMessageLen = 64 * 1024
+	k, in := newTestKafka()
+	k.MaxMessageLen = maxMessageLen
+	acc := testutil.Accumulator{}
+	k.acc = &acc
+	defer close(k.done)
+	overlongMsg := strings.Repeat("v", maxMessageLen+1)
+
+	go k.receiver()
+	in <- saramaMsg(overlongMsg)
+	acc.WaitError(1)
+
+	assert.Equal(t, acc.NFields(), 0)
+}
+
 // Test that the parser parses kafka messages into points
 func TestRunParserAndGather(t *testing.T) {
 	k, in := newTestKafka()