Remove warning if parse empty content (influxdata#2500)

closes influxdata#2448

CHANGELOG.md

@@ -76,6 +76,7 @@ be deprecated eventually.
 - [#2215](https://github.com/influxdata/telegraf/issues/2215): Iptables input: document better that rules without a comment are ignored.
 - [#2483](https://github.com/influxdata/telegraf/pull/2483): Fix win_perf_counters capping values at 100.
 - [#2498](https://github.com/influxdata/telegraf/pull/2498): Exporting Ipmi.Path to be set by config.
+- [#2500](https://github.com/influxdata/telegraf/pull/2500): Remove warning if parse empty content
 
 ## v1.2.1 [2017-02-01]
 

metric/parse.go

@@ -44,6 +44,9 @@ func Parse(buf []byte) ([]telegraf.Metric, error) {
 }
 
 func ParseWithDefaultTime(buf []byte, t time.Time) ([]telegraf.Metric, error) {
+	if len(buf) == 0 {
+		return []telegraf.Metric{}, nil
+	}
 	if len(buf) <= 6 {
 		return []telegraf.Metric{}, makeError("buffer too short", buf, 0)
 	}

plugins/inputs/exec/exec_test.go

@@ -37,6 +37,8 @@ const malformedJson = `
 `
 
 const lineProtocol = "cpu,host=foo,datacenter=us-east usage_idle=99,usage_busy=1\n"
+const lineProtocolEmpty = ""
+const lineProtocolShort = "ab"
 
 const lineProtocolMulti = `
 cpu,cpu=cpu0,host=foo,datacenter=us-east usage_idle=99,usage_busy=1
@@ -167,6 +169,33 @@ func TestLineProtocolParse(t *testing.T) {
 	acc.AssertContainsTaggedFields(t, "cpu", fields, tags)
 }
 
+func TestLineProtocolEmptyParse(t *testing.T) {
+	parser, _ := parsers.NewInfluxParser()
+	e := &Exec{
+		runner:   newRunnerMock([]byte(lineProtocolEmpty), nil),
+		Commands: []string{"line-protocol"},
+		parser:   parser,
+	}
+
+	var acc testutil.Accumulator
+	err := e.Gather(&acc)
+	require.NoError(t, err)
+}
+
+func TestLineProtocolShortParse(t *testing.T) {
+	parser, _ := parsers.NewInfluxParser()
+	e := &Exec{
+		runner:   newRunnerMock([]byte(lineProtocolShort), nil),
+		Commands: []string{"line-protocol"},
+		parser:   parser,
+	}
+
+	var acc testutil.Accumulator
+	err := e.Gather(&acc)
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "buffer too short", "A buffer too short error was expected")
+}
+
 func TestLineProtocolParseMultiple(t *testing.T) {
 	parser, _ := parsers.NewInfluxParser()
 	e := &Exec{