Add expvar JSON @ /debug/vars

Counters include:
 - Uptime
 - SMTP connections
 - SMTP connections (current)
 - SMTP messages delivered

smtpd/handler.go

@@ -88,7 +88,9 @@ func (ss *Session) String() string {
  */
 func (s *Server) startSession(id int, conn net.Conn) {
 	log.Info("Connection from %v, starting session <%v>", conn.RemoteAddr(), id)
+	expConnectsCurrent.Add(1)
 	defer conn.Close()
+	defer expConnectsCurrent.Add(-1)
 
 	ss := NewSession(s, id, conn)
 	ss.greet()
@@ -316,6 +318,7 @@ func (ss *Session) dataHandler() {
 			// Mail data complete
 			for _, m := range messages {
 				m.Close()
+				expDeliveredTotal.Add(1)
 			}
 			ss.send("250 Mail accepted for delivery")
 			ss.info("Message size %v bytes", msgSize)

smtpd/listener.go

@@ -1,6 +1,7 @@
 package smtpd
 
 import (
+	"expvar"
 	"fmt"
 	"github.com/jhillyerd/inbucket/config"
 	"github.com/jhillyerd/inbucket/log"
@@ -16,6 +17,10 @@ type Server struct {
 	dataStore       *DataStore
 }
 
+var expConnectsTotal = new(expvar.Int)
+var expConnectsCurrent = new(expvar.Int)
+var expDeliveredTotal = new(expvar.Int)
+
 // Init a new Server object
 func New() *Server {
 	ds := NewDataStore()
@@ -49,7 +54,15 @@ func (s *Server) Start() {
 			// or maybe attempt to restart smtpd
 			panic(err)
 		} else {
+			expConnectsTotal.Add(1)
 			go s.startSession(sid, conn)
 		}
 	}
 }
+
+func init() {
+	m := expvar.NewMap("smtp")
+	m.Set("connectsTotal", expConnectsTotal)
+	m.Set("connectsCurrent", expConnectsCurrent)
+	m.Set("deliveredTotal", expDeliveredTotal)
+}