Merge pull request #216 from heroku/sherryyao-branch

Set up a pprof server with optional mutex profiling in cmdutil

Description

We want to configure the pprof listener that is capable of running mutex profiles on server set-up in cmdutil/debug. This PR created a new NewPprofServer method to the cmdutil/debug package, allowing for the setup of a pprof server with configurable profiling types and optional mutex profiling.

Changes

Add PProfServerConfig struct: holds configuration for the pprof server.
Add PProfServer struct: wraps a pprof server
Implement NewPProfServer function: creates and configures the pprof server.
Implement Run and Stop methods: the NewPProfServer function includes Run and Stop methods for managing the pprof server lifecycle.
Write unit tests for NewPProfServer

Author: sherryyaosf

cmdutil/debug/debug.go

@@ -15,7 +15,12 @@
 package debug
 
 import (
+	"context"
 	"fmt"
+	"net/http"
+	"net/http/pprof"
+	"runtime"
+	"time"
 
 	"github.com/google/gops/agent"
 	"github.com/sirupsen/logrus"
@@ -71,3 +76,83 @@ func (s *Server) Stop(_ error) {
 
 	close(s.done)
 }
+
+// PProfServer wraps a pprof server.
+type PProfServer struct {
+	logger      logrus.FieldLogger
+	addr        string
+	done        chan struct{}
+	pprofServer *http.Server
+}
+
+// ProfileConfig holds the configuration for the pprof server.
+type PProfServerConfig struct {
+	Addr                 string
+	MutexProfileFraction int
+}
+
+// defaultMutexProfileFraction is the default value for MutexProfileFraction
+const defaultMutexProfileFraction = 2
+
+// NewPProfServer sets up a pprof server with configurable profiling types and returns a PProfServer instance.
+func NewPProfServer(config PProfServerConfig, l logrus.FieldLogger) *PProfServer {
+	if config.Addr == "" {
+		config.Addr = "127.0.0.1:9998" // Default port
+	}
+
+	// Use a local variable for the mutex profile fraction
+	mpf := defaultMutexProfileFraction
+	if config.MutexProfileFraction != 0 {
+		mpf = config.MutexProfileFraction
+	}
+	runtime.SetMutexProfileFraction(mpf)
+
+	httpServer := &http.Server{
+		Addr:              config.Addr,
+		Handler:           http.HandlerFunc(pprof.Index),
+		ReadHeaderTimeout: 5 * time.Second,
+	}
+
+	return &PProfServer{
+		logger:      l,
+		addr:        config.Addr,
+		done:        make(chan struct{}),
+		pprofServer: httpServer,
+	}
+}
+
+// Run starts the pprof server.
+//
+// It implements oklog group's runFn.
+func (s *PProfServer) Run() error {
+	if s.pprofServer == nil {
+		return fmt.Errorf("pprofServer is nil")
+	}
+
+	s.logger.WithFields(logrus.Fields{
+		"at":      "binding",
+		"service": "pprof",
+		"addr":    s.addr,
+	}).Info()
+
+	if err := s.pprofServer.ListenAndServe(); err != nil && err != http.ErrServerClosed {
+		return err
+	}
+
+	<-s.done
+	return nil
+}
+
+// Stop shuts down the pprof server.
+//
+// It implements oklog group's interruptFn.
+func (s *PProfServer) Stop(_ error) {
+	if s.pprofServer != nil {
+		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+		if err := s.pprofServer.Shutdown(ctx); err != nil {
+			s.logger.WithError(err).Error("Error shutting down pprof server")
+		}
+	}
+	close(s.done)
+}

cmdutil/debug/debug_test.go

@@ -0,0 +1,100 @@
+package debug
+
+import (
+	"net/http"
+	"runtime"
+	"testing"
+	"time"
+
+	"github.com/sirupsen/logrus"
+)
+
+func TestNewPProfServer(t *testing.T) {
+	logger := logrus.New()
+
+	tests := []struct {
+		name                  string
+		config                PProfServerConfig
+		expectedAddr          string
+		expectedMutexFraction int
+	}{
+		{
+			name:                  "DefaultAddr",
+			config:                PProfServerConfig{},
+			expectedAddr:          "127.0.0.1:9998",
+			expectedMutexFraction: defaultMutexProfileFraction,
+		},
+		{
+			name:                  "CustomAddr",
+			config:                PProfServerConfig{Addr: "127.0.0.1:9090"},
+			expectedAddr:          "127.0.0.1:9090",
+			expectedMutexFraction: defaultMutexProfileFraction,
+		},
+		{
+			name:                  "CustomMutexProfileFraction",
+			config:                PProfServerConfig{MutexProfileFraction: 5},
+			expectedAddr:          "127.0.0.1:9998",
+			expectedMutexFraction: 5,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			server := NewPProfServer(tt.config, logger)
+
+			// Check server address
+			if server.addr != tt.expectedAddr {
+				t.Errorf("NewPProfServer() addr = %v, want %v", server.addr, tt.expectedAddr)
+			}
+
+			// Start the server
+			go func() {
+				if err := server.Run(); err != nil {
+					t.Errorf("NewPProfServer() run error = %v", err)
+				}
+			}()
+
+			// Give the server a moment to start
+			time.Sleep(100 * time.Millisecond)
+
+			// Check mutex profile fraction
+			if got := runtime.SetMutexProfileFraction(0); got != tt.expectedMutexFraction {
+				t.Errorf("runtime.SetMutexProfileFraction() = %v, want %v", got, tt.expectedMutexFraction)
+			}
+			runtime.SetMutexProfileFraction(tt.expectedMutexFraction) // Reset to the expected value
+
+			// Perform HTTP GET request to the root path
+			url := "http://" + server.addr + "/debug/pprof/"
+			client := &http.Client{}
+
+			t.Run("GET "+url, func(t *testing.T) {
+				req, err := http.NewRequest("GET", url, nil)
+				if err != nil {
+					t.Errorf("http.NewRequest(%s) error = %v", url, err)
+				}
+
+				resp, err := client.Do(req)
+				if err != nil {
+					t.Errorf("http.Client.Do() error = %v", err)
+				}
+
+				if resp.StatusCode != http.StatusOK {
+					t.Errorf("http.Client.Do() status = %v, want %v", resp.StatusCode, http.StatusOK)
+				}
+
+				resp.Body.Close()
+			})
+
+			// Stop the server
+			server.Stop(nil)
+
+			// Ensure the server is stopped
+			select {
+			case <-server.done:
+				// success
+			case <-time.After(1 * time.Second):
+				t.Fatal("server did not stop in time")
+			}
+		})
+	}
+}