Add pprof server for steve binary (#886)

* Add pprof server for steve binary

* Add link to graphviz

Author: tomleb

README.md

@@ -452,6 +452,22 @@ go run main.go
 
 The API can be accessed by navigating to https://localhost:9443/v1.
 
+### Running the pprof server
+
+You can enable the `pprof` http server when running steve as a binary by
+enabling pprof with `--enable-pprof`.
+
+```
+go run . --enable-pprof
+```
+
+It is then possible to use `go tool pprof` to view profiles. (You might need
+[graphviz](https://www.graphviz.org/)) For example:
+
+```
+go tool pprof -no_browser -http localhost:31000 http://localhost:6060/debug/pprof/goroutine
+```
+
 Steve Features
 --------------
 

main.go

@@ -1,6 +1,8 @@
 package main
 
 import (
+	"net/http"
+	_ "net/http/pprof"
 	"os"
 
 	"github.com/rancher/dynamiclistener/server"
@@ -39,5 +41,12 @@ func run(_ *cli.Context) error {
 	if err != nil {
 		return err
 	}
+	if config.PprofEnabled {
+		go func() {
+			if err := http.ListenAndServe(config.PprofListenAddr, nil); err != nil {
+				logrus.Fatalf("pprof server: %v\n", err)
+			}
+		}()
+	}
 	return s.ListenAndServe(ctx, config.HTTPSListenPort, config.HTTPListenPort, &server.ListenOpts{DisplayServerLogs: true})
 }

pkg/server/cli/clicontext.go

@@ -21,6 +21,9 @@ type Config struct {
 	HTTPListenPort  int
 	UIPath          string
 
+	PprofEnabled    bool
+	PprofListenAddr string
+
 	WebhookConfig authcli.WebhookConfig
 }
 
@@ -87,6 +90,16 @@ func Flags(config *Config) []cli.Flag {
 			Value:       9080,
 			Destination: &config.HTTPListenPort,
 		},
+		&cli.BoolFlag{
+			Name:        "enable-pprof",
+			Value:       false,
+			Destination: &config.PprofEnabled,
+		},
+		&cli.StringFlag{
+			Name:        "pprof-listen-addr",
+			Value:       "localhost:6060",
+			Destination: &config.PprofListenAddr,
+		},
 	}
 
 	return append(flags, authcli.Flags(&config.WebhookConfig)...)