core: metrics v2 (#1370)

* outposts: add ldap metrics, move ping to 9100

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* outpost: add flow_executor metrics

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* use port 9300 for metrics, add core metrics port

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

* outposts/controllers/k8s: add service monitor creation support

Signed-off-by: Jens Langhammer <jens.langhammer@beryju.org>

internal/web/utils.go

@@ -0,0 +1,31 @@
+package web
+
+import (
+	"log"
+	"net"
+	"time"
+)
+
+// tcpKeepAliveListener sets TCP keep-alive timeouts on accepted
+// connections. It's used by ListenAndServe and ListenAndServeTLS so
+// dead TCP connections (e.g. closing laptop mid-download) eventually
+// go away.
+type tcpKeepAliveListener struct {
+	*net.TCPListener
+}
+
+func (ln tcpKeepAliveListener) Accept() (net.Conn, error) {
+	tc, err := ln.AcceptTCP()
+	if err != nil {
+		return nil, err
+	}
+	err = tc.SetKeepAlive(true)
+	if err != nil {
+		log.Printf("Error setting Keep-Alive: %v", err)
+	}
+	err = tc.SetKeepAlivePeriod(3 * time.Minute)
+	if err != nil {
+		log.Printf("Error setting Keep-Alive period: %v", err)
+	}
+	return tc, nil
+}