Renamed self.go

http.go

@@ -1,11 +0,0 @@
-package main
-
-import (
-	_ "expvar"
-	"net/http"
-)
-
-func StartHttp(bind string) {
-	// silently discard error here
-	http.ListenAndServe(":"+bind, nil)
-}

self.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"expvar"
+	"fmt"
+	"net"
+	"net/http"
+	"runtime"
+	"time"
+)
+
+var startTime = time.Now().UTC()
+
+func goroutines() interface{} {
+	return runtime.NumGoroutine()
+}
+
+// uptime is an expvar.Func compliant wrapper for uptime info.
+func uptime() interface{} {
+	uptime := time.Since(startTime)
+	return int64(uptime)
+}
+
+// startPort defines lower port for bind
+const startPort = 32768
+
+// StartSelfMonitor starts http server on random port and exports expvars.
+//
+// It tries 1024 ports, starting from startPort and registers some expvars if ok.
+func StartSelfMonitor() (string, error) {
+	for port := startPort; port < startPort+1024; port++ {
+		bind := fmt.Sprintf("localhost:%d", port)
+		l, err := net.Listen("tcp", bind)
+		if err != nil {
+			continue
+		}
+		l.Close()
+
+		expvar.Publish("Goroutines", expvar.Func(goroutines))
+		expvar.Publish("Uptime", expvar.Func(uptime))
+		go http.ListenAndServe(bind, nil)
+		return bind, nil
+	}
+
+	return "", fmt.Errorf("no free ports found")
+}