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.go

@@ -0,0 +1,99 @@
+package client
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"net"
+	"net/url"
+)
+
+const (
+	// UDPPayloadSize is a reasonable default payload size for UDP packets that
+	// could be travelling over the internet.
+	UDPPayloadSize = 512
+)
+
+// UDPConfig is the config data needed to create a UDP Client
+type UDPConfig struct {
+	// URL should be of the form "udp://host:port"
+	// or "udp://[ipv6-host%zone]:port".
+	URL string
+
+	// PayloadSize is the maximum size of a UDP client message, optional
+	// Tune this based on your network. Defaults to UDPPayloadSize.
+	PayloadSize int
+}
+
+func NewUDP(config UDPConfig) (Client, error) {
+	p, err := url.Parse(config.URL)
+	if err != nil {
+		return nil, fmt.Errorf("Error parsing UDP url [%s]: %s", config.URL, err)
+	}
+
+	udpAddr, err := net.ResolveUDPAddr("udp", p.Host)
+	if err != nil {
+		return nil, fmt.Errorf("Error resolving UDP Address [%s]: %s", p.Host, err)
+	}
+
+	conn, err := net.DialUDP("udp", nil, udpAddr)
+	if err != nil {
+		return nil, fmt.Errorf("Error dialing UDP address [%s]: %s",
+			udpAddr.String(), err)
+	}
+
+	size := config.PayloadSize
+	if size == 0 {
+		size = UDPPayloadSize
+	}
+	buf := make([]byte, size)
+	return &udpClient{conn: conn, buffer: buf}, nil
+}
+
+type udpClient struct {
+	conn   *net.UDPConn
+	buffer []byte
+}
+
+func (c *udpClient) Query(command string) error {
+	return nil
+}
+
+func (c *udpClient) Write(b []byte) (int, error) {
+	return c.WriteStream(bytes.NewReader(b), -1)
+}
+
+// write params are ignored by the UDP client
+func (c *udpClient) WriteWithParams(b []byte, wp WriteParams) (int, error) {
+	return c.WriteStream(bytes.NewReader(b), -1)
+}
+
+// contentLength is ignored by the UDP client.
+func (c *udpClient) WriteStream(r io.Reader, contentLength int) (int, error) {
+	var totaln int
+	for {
+		nR, err := r.Read(c.buffer)
+		if nR == 0 {
+			break
+		}
+		if err != io.EOF && err != nil {
+			return totaln, err
+		}
+		nW, err := c.conn.Write(c.buffer[0:nR])
+		totaln += nW
+		if err != nil {
+			return totaln, err
+		}
+	}
+	return totaln, nil
+}
+
+// contentLength is ignored by the UDP client.
+// write params are ignored by the UDP client
+func (c *udpClient) WriteStreamWithParams(r io.Reader, contentLength int, wp WriteParams) (int, error) {
+	return c.WriteStream(r, -1)
+}
+
+func (c *udpClient) Close() error {
+	return c.conn.Close()
+}