Refactor docs; Add 'ipng_source_tag', add udp listener for nginx-ipng-stats plugin

cmd/collector/udp.go

@@ -0,0 +1,86 @@
+package main
+
+import (
+	"context"
+	"log"
+	"net"
+	"strings"
+)
+
+// udpReadBufBytes is the SO_RCVBUF size requested. Bursts of ~10K lines/sec at
+// ~200B each comfortably fit; the kernel may cap below this.
+const udpReadBufBytes = 4 << 20
+
+// udpPacketBuf is the per-read buffer. A single nginx log line easily fits in
+// a few KB; 64K is the practical UDP datagram ceiling.
+const udpPacketBuf = 64 << 10
+
+// UDPListener receives nginx_ipng_stats_logtail datagrams on a local socket,
+// parses each packet as one log line, and forwards LogRecords to ch.
+type UDPListener struct {
+	addr   string
+	v4bits int
+	v6bits int
+	ch     chan<- LogRecord
+	prom   *PromStore // optional; bumps UDP ingest counters
+}
+
+func NewUDPListener(addr string, v4bits, v6bits int, ch chan<- LogRecord) *UDPListener {
+	return &UDPListener{addr: addr, v4bits: v4bits, v6bits: v6bits, ch: ch}
+}
+
+// SetProm wires a PromStore so the listener can report received/success/consumed counts.
+func (u *UDPListener) SetProm(p *PromStore) { u.prom = p }
+
+// Run listens until ctx is cancelled.
+func (u *UDPListener) Run(ctx context.Context) {
+	laddr, err := net.ResolveUDPAddr("udp", u.addr)
+	if err != nil {
+		log.Fatalf("udp: resolve %s: %v", u.addr, err)
+	}
+	conn, err := net.ListenUDP("udp", laddr)
+	if err != nil {
+		log.Fatalf("udp: listen %s: %v", u.addr, err)
+	}
+	defer conn.Close()
+	if err := conn.SetReadBuffer(udpReadBufBytes); err != nil {
+		log.Printf("udp: SetReadBuffer(%d): %v", udpReadBufBytes, err)
+	}
+	log.Printf("udp: listening on %s", conn.LocalAddr())
+
+	go func() {
+		<-ctx.Done()
+		conn.Close()
+	}()
+
+	buf := make([]byte, udpPacketBuf)
+	for {
+		n, _, err := conn.ReadFromUDP(buf)
+		if err != nil {
+			if ctx.Err() != nil {
+				return
+			}
+			log.Printf("udp: read: %v", err)
+			continue
+		}
+		if u.prom != nil {
+			u.prom.IncUDPPacket()
+		}
+		line := strings.TrimRight(string(buf[:n]), "\r\n")
+		rec, ok := ParseUDPLine(line, u.v4bits, u.v6bits)
+		if !ok {
+			continue
+		}
+		if u.prom != nil {
+			u.prom.IncUDPSuccess()
+		}
+		select {
+		case u.ch <- rec:
+			if u.prom != nil {
+				u.prom.IncUDPConsumed()
+			}
+		default:
+			// Channel full — drop rather than block the read loop.
+		}
+	}
+}