plugin/dnstap: remove config struct (#4258)

* plugin/dnstap: remove config struct

this struct is an uneeded intermidiate to get a dnstap it can be
removed. Remove the dnstapio subpkg: it's also not needed. Make *many*
functions and structs private now that we can.

Signed-off-by: Miek Gieben <miek@miek.nl>

* correct logging

Signed-off-by: Miek Gieben <miek@miek.nl>

plugin/dnstap/io.go

@@ -0,0 +1,121 @@
+package dnstap
+
+import (
+	"net"
+	"sync/atomic"
+	"time"
+
+	tap "github.com/dnstap/golang-dnstap"
+)
+
+const (
+	tcpWriteBufSize = 1024 * 1024 // there is no good explanation for why this number has this value.
+	queueSize       = 10000       // idem.
+
+	tcpTimeout   = 4 * time.Second
+	flushTimeout = 1 * time.Second
+)
+
+// tapper interface is used in testing to mock the Dnstap method.
+type tapper interface {
+	Dnstap(tap.Dnstap)
+}
+
+// dio implements the Tapper interface.
+type dio struct {
+	endpoint     string
+	proto        string
+	conn         net.Conn
+	enc          *encoder
+	queue        chan tap.Dnstap
+	dropped      uint32
+	quit         chan struct{}
+	flushTimeout time.Duration
+	tcpTimeout   time.Duration
+}
+
+// newIO returns a new and initialized pointer to a dio.
+func newIO(proto, endpoint string) *dio {
+	return &dio{
+		endpoint:     endpoint,
+		proto:        proto,
+		queue:        make(chan tap.Dnstap, queueSize),
+		quit:         make(chan struct{}),
+		flushTimeout: flushTimeout,
+		tcpTimeout:   tcpTimeout,
+	}
+}
+
+func (d *dio) dial() error {
+	conn, err := net.DialTimeout(d.proto, d.endpoint, d.tcpTimeout)
+	if err != nil {
+		return err
+	}
+	if tcpConn, ok := conn.(*net.TCPConn); ok {
+		tcpConn.SetWriteBuffer(tcpWriteBufSize)
+		tcpConn.SetNoDelay(false)
+	}
+
+	d.enc, err = newEncoder(conn, d.tcpTimeout)
+	return err
+}
+
+// Connect connects to the dnstap endpoint.
+func (d *dio) connect() error {
+	err := d.dial()
+	go d.serve()
+	return err
+}
+
+// Dnstap enqueues the payload for log.
+func (d *dio) Dnstap(payload tap.Dnstap) {
+	select {
+	case d.queue <- payload:
+	default:
+		atomic.AddUint32(&d.dropped, 1)
+	}
+}
+
+// close waits until the I/O routine is finished to return.
+func (d *dio) close() { close(d.quit) }
+
+func (d *dio) write(payload *tap.Dnstap) error {
+	if d.enc == nil {
+		atomic.AddUint32(&d.dropped, 1)
+		return nil
+	}
+	if err := d.enc.writeMsg(payload); err != nil {
+		atomic.AddUint32(&d.dropped, 1)
+		return err
+	}
+	return nil
+}
+
+func (d *dio) serve() {
+	timeout := time.After(d.flushTimeout)
+	for {
+		select {
+		case <-d.quit:
+			if d.enc == nil {
+				return
+			}
+			d.enc.flush()
+			d.enc.close()
+			return
+		case payload := <-d.queue:
+			if err := d.write(&payload); err != nil {
+				d.dial()
+			}
+		case <-timeout:
+			if dropped := atomic.SwapUint32(&d.dropped, 0); dropped > 0 {
+				log.Warningf("Dropped dnstap messages: %d", dropped)
+			}
+			if d.enc == nil {
+				d.dial()
+			} else {
+				d.enc.flush()
+			}
+			timeout = time.After(d.flushTimeout)
+		}
+	}
+}