Improve the InfluxDB through-put performance

This changes the current use of the InfluxDB client to instead use a
baked-in client that uses the fasthttp library.

This allows for significantly smaller allocations, the re-use of http
body buffers, and the re-use of the actual bytes of the line-protocol
metric representations.

plugins/outputs/influxdb/client/udp_test.go

@@ -0,0 +1,163 @@
+package client
+
+import (
+	"bytes"
+	"net"
+	"testing"
+	"time"
+
+	"github.com/influxdata/telegraf"
+	"github.com/influxdata/telegraf/metric"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestUDPClient(t *testing.T) {
+	config := UDPConfig{
+		URL: "udp://localhost:8089",
+	}
+	client, err := NewUDP(config)
+	assert.NoError(t, err)
+
+	err = client.Query("ANY QUERY RETURNS NIL")
+	assert.NoError(t, err)
+
+	assert.NoError(t, client.Close())
+}
+
+func TestNewUDPClient_Errors(t *testing.T) {
+	// url.Parse Error
+	config := UDPConfig{
+		URL: "udp://localhost%35:8089",
+	}
+	_, err := NewUDP(config)
+	assert.Error(t, err)
+
+	// ResolveUDPAddr Error
+	config = UDPConfig{
+		URL: "udp://localhost:999999",
+	}
+	_, err = NewUDP(config)
+	assert.Error(t, err)
+}
+
+func TestUDPClient_Write(t *testing.T) {
+	config := UDPConfig{
+		URL: "udp://localhost:8199",
+	}
+	client, err := NewUDP(config)
+	assert.NoError(t, err)
+
+	packets := make(chan string, 100)
+	address, err := net.ResolveUDPAddr("udp", "localhost:8199")
+	assert.NoError(t, err)
+	listener, err := net.ListenUDP("udp", address)
+	defer listener.Close()
+	assert.NoError(t, err)
+	go func() {
+		buf := make([]byte, 200)
+		for {
+			n, _, err := listener.ReadFromUDP(buf)
+			if err != nil {
+				packets <- err.Error()
+			}
+			packets <- string(buf[0:n])
+		}
+	}()
+
+	// test sending simple metric
+	time.Sleep(time.Second)
+	n, err := client.Write([]byte("cpu value=99\n"))
+	assert.Equal(t, n, 13)
+	assert.NoError(t, err)
+	pkt := <-packets
+	assert.Equal(t, "cpu value=99\n", pkt)
+
+	metrics := `cpu value=99
+cpu value=55
+cpu value=44
+cpu value=101
+cpu value=91
+cpu value=92
+`
+	// test sending packet with 6 metrics in a stream.
+	reader := bytes.NewReader([]byte(metrics))
+	// contentLength is ignored:
+	n, err = client.WriteStream(reader, 10)
+	assert.Equal(t, n, len(metrics))
+	assert.NoError(t, err)
+	pkt = <-packets
+	assert.Equal(t, "cpu value=99\ncpu value=55\ncpu value=44\ncpu value=101\ncpu value=91\ncpu value=92\n", pkt)
+
+	//
+	// Test that UDP packets get broken up properly:
+	config2 := UDPConfig{
+		URL:         "udp://localhost:8199",
+		PayloadSize: 25,
+	}
+	client2, err := NewUDP(config2)
+	assert.NoError(t, err)
+
+	wp := WriteParams{}
+
+	//
+	// Using Write():
+	buf := []byte(metrics)
+	n, err = client2.WriteWithParams(buf, wp)
+	assert.Equal(t, n, len(metrics))
+	assert.NoError(t, err)
+	pkt = <-packets
+	assert.Equal(t, "cpu value=99\ncpu value=55", pkt)
+	pkt = <-packets
+	assert.Equal(t, "\ncpu value=44\ncpu value=1", pkt)
+	pkt = <-packets
+	assert.Equal(t, "01\ncpu value=91\ncpu value", pkt)
+	pkt = <-packets
+	assert.Equal(t, "=92\n", pkt)
+
+	//
+	// Using WriteStream():
+	reader = bytes.NewReader([]byte(metrics))
+	n, err = client2.WriteStreamWithParams(reader, 10, wp)
+	assert.Equal(t, n, len(metrics))
+	assert.NoError(t, err)
+	pkt = <-packets
+	assert.Equal(t, "cpu value=99\ncpu value=55", pkt)
+	pkt = <-packets
+	assert.Equal(t, "\ncpu value=44\ncpu value=1", pkt)
+	pkt = <-packets
+	assert.Equal(t, "01\ncpu value=91\ncpu value", pkt)
+	pkt = <-packets
+	assert.Equal(t, "=92\n", pkt)
+
+	//
+	// Using WriteStream() & a metric.Reader:
+	config3 := UDPConfig{
+		URL:         "udp://localhost:8199",
+		PayloadSize: 40,
+	}
+	client3, err := NewUDP(config3)
+	assert.NoError(t, err)
+
+	now := time.Unix(1484142942, 0)
+	m1, _ := metric.New("test", map[string]string{},
+		map[string]interface{}{"value": 1.1}, now)
+	m2, _ := metric.New("test", map[string]string{},
+		map[string]interface{}{"value": 1.1}, now)
+	m3, _ := metric.New("test", map[string]string{},
+		map[string]interface{}{"value": 1.1}, now)
+	ms := []telegraf.Metric{m1, m2, m3}
+	mReader := metric.NewReader(ms)
+	n, err = client3.WriteStreamWithParams(mReader, 10, wp)
+	// 3 metrics at 35 bytes each (including the newline)
+	assert.Equal(t, 105, n)
+	assert.NoError(t, err)
+	pkt = <-packets
+	assert.Equal(t, "test value=1.1 1484142942000000000\n", pkt)
+	pkt = <-packets
+	assert.Equal(t, "test value=1.1 1484142942000000000\n", pkt)
+	pkt = <-packets
+	assert.Equal(t, "test value=1.1 1484142942000000000\n", pkt)
+
+	assert.NoError(t, client.Close())
+}