'discard' output plugin

plugins/outputs/all/all.go

@@ -5,6 +5,7 @@ import (
 	_ "github.com/influxdata/telegraf/plugins/outputs/amqp"
 	_ "github.com/influxdata/telegraf/plugins/outputs/cloudwatch"
 	_ "github.com/influxdata/telegraf/plugins/outputs/datadog"
+	_ "github.com/influxdata/telegraf/plugins/outputs/discard"
 	_ "github.com/influxdata/telegraf/plugins/outputs/file"
 	_ "github.com/influxdata/telegraf/plugins/outputs/graphite"
 	_ "github.com/influxdata/telegraf/plugins/outputs/graylog"

plugins/outputs/discard/README.md

@@ -0,0 +1,12 @@
+# discard Output Plugin
+
+This output plugin simply drops all metrics that are sent to it. It is only
+meant to be used for testing purposes.
+
+### Configuration:
+
+```toml
+# Send metrics to nowhere at all
+[[outputs.discard]]
+  # no configuration
+```

plugins/outputs/discard/discard.go

@@ -0,0 +1,35 @@
+package discard
+
+import (
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/plugins/outputs"
+)
+
+type Discard struct {
+}
+
+func (d *Discard) Connect() error {
+	return nil
+}
+
+func (d *Discard) Close() error {
+	return nil
+}
+
+func (d *Discard) SampleConfig() string {
+	return ""
+}
+
+func (d *Discard) Description() string {
+	return "Send metrics to nowhere at all"
+}
+
+func (d *Discard) Write(metrics []telegraf.Metric) error {
+	return nil
+}
+
+func init() {
+	outputs.Add("discard", func() telegraf.Output {
+		return &Discard{}
+	})
+}

plugins/outputs/discard/discard_test.go

@@ -0,0 +1,196 @@
+package discard
+
+import (
+	"bytes"
+	"io"
+	"io/ioutil"
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+
+	"github.com/influxdata/telegraf/internal"
+	"github.com/influxdata/telegraf/plugins/serializers"
+	"github.com/influxdata/telegraf/testutil"
+)
+
+const (
+	expNewFile   = "test1,tag1=value1 value=1 1257894000000000000\n"
+	expExistFile = "cpu,cpu=cpu0 value=100 1455312810012459582\n" +
+		"test1,tag1=value1 value=1 1257894000000000000\n"
+)
+
+func TestFileExistingFile(t *testing.T) {
+	fh := createFile()
+	s, _ := serializers.NewInfluxSerializer()
+	f := File{
+		Files:      []string{fh.Name()},
+		serializer: s,
+	}
+
+	err := f.Connect()
+	assert.NoError(t, err)
+
+	err = f.Write(testutil.MockMetrics())
+	assert.NoError(t, err)
+
+	validateFile(fh.Name(), expExistFile, t)
+
+	err = f.Close()
+	assert.NoError(t, err)
+}
+
+func TestFileNewFile(t *testing.T) {
+	s, _ := serializers.NewInfluxSerializer()
+	fh := tmpFile()
+	f := File{
+		Files:      []string{fh},
+		serializer: s,
+	}
+
+	err := f.Connect()
+	assert.NoError(t, err)
+
+	err = f.Write(testutil.MockMetrics())
+	assert.NoError(t, err)
+
+	validateFile(fh, expNewFile, t)
+
+	err = f.Close()
+	assert.NoError(t, err)
+}
+
+func TestFileExistingFiles(t *testing.T) {
+	fh1 := createFile()
+	fh2 := createFile()
+	fh3 := createFile()
+
+	s, _ := serializers.NewInfluxSerializer()
+	f := File{
+		Files:      []string{fh1.Name(), fh2.Name(), fh3.Name()},
+		serializer: s,
+	}
+
+	err := f.Connect()
+	assert.NoError(t, err)
+
+	err = f.Write(testutil.MockMetrics())
+	assert.NoError(t, err)
+
+	validateFile(fh1.Name(), expExistFile, t)
+	validateFile(fh2.Name(), expExistFile, t)
+	validateFile(fh3.Name(), expExistFile, t)
+
+	err = f.Close()
+	assert.NoError(t, err)
+}
+
+func TestFileNewFiles(t *testing.T) {
+	s, _ := serializers.NewInfluxSerializer()
+	fh1 := tmpFile()
+	fh2 := tmpFile()
+	fh3 := tmpFile()
+	f := File{
+		Files:      []string{fh1, fh2, fh3},
+		serializer: s,
+	}
+
+	err := f.Connect()
+	assert.NoError(t, err)
+
+	err = f.Write(testutil.MockMetrics())
+	assert.NoError(t, err)
+
+	validateFile(fh1, expNewFile, t)
+	validateFile(fh2, expNewFile, t)
+	validateFile(fh3, expNewFile, t)
+
+	err = f.Close()
+	assert.NoError(t, err)
+}
+
+func TestFileBoth(t *testing.T) {
+	fh1 := createFile()
+	fh2 := tmpFile()
+
+	s, _ := serializers.NewInfluxSerializer()
+	f := File{
+		Files:      []string{fh1.Name(), fh2},
+		serializer: s,
+	}
+
+	err := f.Connect()
+	assert.NoError(t, err)
+
+	err = f.Write(testutil.MockMetrics())
+	assert.NoError(t, err)
+
+	validateFile(fh1.Name(), expExistFile, t)
+	validateFile(fh2, expNewFile, t)
+
+	err = f.Close()
+	assert.NoError(t, err)
+}
+
+func TestFileStdout(t *testing.T) {
+	// keep backup of the real stdout
+	old := os.Stdout
+	r, w, _ := os.Pipe()
+	os.Stdout = w
+
+	s, _ := serializers.NewInfluxSerializer()
+	f := File{
+		Files:      []string{"stdout"},
+		serializer: s,
+	}
+
+	err := f.Connect()
+	assert.NoError(t, err)
+
+	err = f.Write(testutil.MockMetrics())
+	assert.NoError(t, err)
+
+	err = f.Close()
+	assert.NoError(t, err)
+
+	outC := make(chan string)
+	// copy the output in a separate goroutine so printing can't block indefinitely
+	go func() {
+		var buf bytes.Buffer
+		io.Copy(&buf, r)
+		outC <- buf.String()
+	}()
+
+	// back to normal state
+	w.Close()
+	// restoring the real stdout
+	os.Stdout = old
+	out := <-outC
+
+	assert.Equal(t, expNewFile, out)
+}
+
+func createFile() *os.File {
+	f, err := ioutil.TempFile("", "")
+	if err != nil {
+		panic(err)
+	}
+	f.WriteString("cpu,cpu=cpu0 value=100 1455312810012459582\n")
+	return f
+}
+
+func tmpFile() string {
+	d, err := ioutil.TempDir("", "")
+	if err != nil {
+		panic(err)
+	}
+	return d + internal.RandomString(10)
+}
+
+func validateFile(fname, expS string, t *testing.T) {
+	buf, err := ioutil.ReadFile(fname)
+	if err != nil {
+		panic(err)
+	}
+	assert.Equal(t, expS, string(buf))
+}