instrumental plugin, rewrite connection retries

closes #1412

separate hello and authenticate functions,
force connection close at end of write cycle so we don't
hold open idle connections,
which has the benefit of mostly removing
the chance of getting hopelessly connection lost

bump instrumental agent version

fix test to deal with better better connect/reconnect logic and changed ident & auth handshake

Update CHANGELOG.md

correct URL from instrumental fork to origin and put the change in the correct part of the file

go fmt

undo split hello and auth commands, to reduce roundtrips

CHANGELOG.md

@@ -48,6 +48,7 @@ should now look like:
 - [#1461](https://github.com/influxdata/telegraf/pull/1461): Prometheus parser, protobuf format header fix.
 - [#1334](https://github.com/influxdata/telegraf/issues/1334): Prometheus output, metric refresh and caching fixes.
 - [#1432](https://github.com/influxdata/telegraf/issues/1432): Panic fix for multiple graphite outputs under very high load.
+- [#1412](https://github.com/influxdata/telegraf/pull/1412): Instrumental output has better reconnect behavior
 
 ## v1.0 beta 2 [2016-06-21]
 

plugins/outputs/instrumental/instrumental.go

@@ -29,7 +29,9 @@ type Instrumental struct {
 
 const (
 	DefaultHost     = "collector.instrumentalapp.com"
-	AuthFormat  = "hello version go/telegraf/1.0\nauthenticate %s\n"
+	HelloMessage    = "hello version go/telegraf/1.1\n"
+	AuthFormat      = "authenticate %s\n"
+	HandshakeFormat = HelloMessage + AuthFormat
 )
 
 var (
@@ -52,6 +54,7 @@ var sampleConfig = `
 
 func (i *Instrumental) Connect() error {
 	connection, err := net.DialTimeout("tcp", i.Host+":8000", i.Timeout.Duration)
+
 	if err != nil {
 		i.conn = nil
 		return err
@@ -151,6 +154,11 @@ func (i *Instrumental) Write(metrics []telegraf.Metric) error {
 		return err
 	}
 
+	// force the connection closed after sending data
+	// to deal with various disconnection scenarios and eschew holding
+	// open idle connections en masse
+	i.Close()
+
 	return nil
 }
 
@@ -163,7 +171,7 @@ func (i *Instrumental) SampleConfig() string {
 }
 
 func (i *Instrumental) authenticate(conn net.Conn) error {
-	_, err := fmt.Fprintf(conn, AuthFormat, i.ApiToken)
+	_, err := fmt.Fprintf(conn, HandshakeFormat, i.ApiToken)
 	if err != nil {
 		return err
 	}

plugins/outputs/instrumental/instrumental_test.go

@@ -24,7 +24,6 @@ func TestWrite(t *testing.T) {
 		ApiToken: "abc123token",
 		Prefix:   "my.prefix",
 	}
-	i.Connect()
 
 	// Default to gauge
 	m1, _ := telegraf.NewMetric(
@@ -40,10 +39,8 @@ func TestWrite(t *testing.T) {
 		time.Date(2010, time.November, 10, 23, 0, 0, 0, time.UTC),
 	)
 
-	// Simulate a connection close and reconnect.
 	metrics := []telegraf.Metric{m1, m2}
 	i.Write(metrics)
-	i.Close()
 
 	// Counter and Histogram are increments
 	m3, _ := telegraf.NewMetric(
@@ -70,7 +67,6 @@ func TestWrite(t *testing.T) {
 	i.Write(metrics)
 
 	wg.Wait()
-	i.Close()
 }
 
 func TCPServer(t *testing.T, wg *sync.WaitGroup) {
@@ -82,10 +78,9 @@ func TCPServer(t *testing.T, wg *sync.WaitGroup) {
 	tp := textproto.NewReader(reader)
 
 	hello, _ := tp.ReadLine()
-	assert.Equal(t, "hello version go/telegraf/1.0", hello)
+	assert.Equal(t, "hello version go/telegraf/1.1", hello)
 	auth, _ := tp.ReadLine()
 	assert.Equal(t, "authenticate abc123token", auth)
-
 	conn.Write([]byte("ok\nok\n"))
 
 	data1, _ := tp.ReadLine()
@@ -99,10 +94,9 @@ func TCPServer(t *testing.T, wg *sync.WaitGroup) {
 	tp = textproto.NewReader(reader)
 
 	hello, _ = tp.ReadLine()
-	assert.Equal(t, "hello version go/telegraf/1.0", hello)
+	assert.Equal(t, "hello version go/telegraf/1.1", hello)
 	auth, _ = tp.ReadLine()
 	assert.Equal(t, "authenticate abc123token", auth)
-
 	conn.Write([]byte("ok\nok\n"))
 
 	data3, _ := tp.ReadLine()