profiling: adds profiling and tracing

If grafana-server binary is started with the -profile flag then
tracing will create a trace.out file and pprof data can be accessed
on the 6060 port.

A custom port for pprof profiling can be set with the -profile-port
flag.

pkg/cmd/grafana-server/main.go

@@ -8,10 +8,14 @@ import (
 	"os/signal"
 	"path/filepath"
 	"runtime"
+	"runtime/trace"
 	"strconv"
 	"syscall"
 	"time"
 
+	"net/http"
+	_ "net/http/pprof"
+
 	"github.com/grafana/grafana/pkg/log"
 	"github.com/grafana/grafana/pkg/models"
 	"github.com/grafana/grafana/pkg/services/sqlstore"
@@ -44,12 +48,33 @@ func init() {
 
 func main() {
 	v := flag.Bool("v", false, "prints current version and exits")
+	profile := flag.Bool("profile", false, "Turn on pprof profiling")
+	profilePort := flag.Int("profile-port", 6060, "Define custom port for profiling")
 	flag.Parse()
 	if *v {
 		fmt.Printf("Version %s (commit: %s)\n", version, commit)
 		os.Exit(0)
 	}
 
+	if *profile {
+		runtime.SetBlockProfileRate(1)
+		go func() {
+			http.ListenAndServe(fmt.Sprintf("localhost:%d", *profilePort), nil)
+		}()
+
+		f, err := os.Create("trace.out")
+		if err != nil {
+			panic(err)
+		}
+		defer f.Close()
+
+		err = trace.Start(f)
+		if err != nil {
+			panic(err)
+		}
+		defer trace.Stop()
+	}
+
 	buildstampInt64, _ := strconv.ParseInt(buildstamp, 10, 64)
 	if buildstampInt64 == 0 {
 		buildstampInt64 = time.Now().Unix()
@@ -113,6 +138,8 @@ func listenToSystemSignals(server models.GrafanaServer) {
 
 	select {
 	case sig := <-signalChan:
+		// Stops trace if profiling has been enabled
+		trace.Stop()
 		server.Shutdown(0, fmt.Sprintf("system signal: %s", sig))
 	case code = <-exitChan:
 		server.Shutdown(code, "startup error")