shim: Move pprof server to plugin

Makes the pprof server a plugin and also gates by the `shim_tracing`
build tag (like otel is).
With this change, `net/http` is no longer a dependency in the shim.

Signed-off-by: Brian Goff <cpuguy83@gmail.com>

cmd/containerd-shim-runc-v2/main_tracing.go

@@ -18,4 +18,7 @@
 
 package main
 
-import _ "github.com/containerd/containerd/v2/pkg/tracing/plugin"
+import (
+	_ "github.com/containerd/containerd/v2/internal/pprof"
+	_ "github.com/containerd/containerd/v2/pkg/tracing/plugin"
+)

internal/pprof/plugin.go

@@ -0,0 +1,55 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package pprof
+
+import (
+	"expvar"
+	"net/http"
+	"net/http/pprof"
+	"time"
+
+	"github.com/containerd/containerd/v2/plugins"
+	"github.com/containerd/plugin"
+	"github.com/containerd/plugin/registry"
+)
+
+const pluginName = "pprof"
+
+func init() {
+	registry.Register(&plugin.Registration{
+		ID:   pluginName,
+		Type: plugins.HTTPHandler,
+		InitFn: func(ic *plugin.InitContext) (interface{}, error) {
+			return newHandler(), nil
+		},
+	})
+}
+
+func newHandler() *http.Server {
+	m := http.NewServeMux()
+	m.Handle("/debug/vars", expvar.Handler())
+	m.Handle("/debug/pprof/", http.HandlerFunc(pprof.Index))
+	m.Handle("/debug/pprof/cmdline", http.HandlerFunc(pprof.Cmdline))
+	m.Handle("/debug/pprof/profile", http.HandlerFunc(pprof.Profile))
+	m.Handle("/debug/pprof/symbol", http.HandlerFunc(pprof.Symbol))
+	m.Handle("/debug/pprof/trace", http.HandlerFunc(pprof.Trace))
+
+	return &http.Server{
+		Handler:           m,
+		ReadHeaderTimeout: 5 * time.Minute,
+	}
+}

pkg/shim/shim.go

@@ -20,13 +20,10 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
-	"expvar"
 	"flag"
 	"fmt"
 	"io"
 	"net"
-	"net/http"
-	"net/http/pprof"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -344,6 +341,8 @@ func run(ctx context.Context, manager Manager, config Config) error {
 		ttrpcServices = []TTRPCService{}
 
 		ttrpcUnaryInterceptors = []ttrpc.UnaryServerInterceptor{}
+
+		pprofHandler server
 	)
 
 	for _, p := range registry.Graph(func(*plugin.Registration) bool { return false }) {
@@ -397,6 +396,10 @@ func run(ctx context.Context, manager Manager, config Config) error {
 			ttrpcUnaryInterceptors = append(ttrpcUnaryInterceptors, src.UnaryServerInterceptor())
 		}
 
+		if result.Registration.ID == "pprof" {
+			if src, ok := instance.(server); ok {
+				pprofHandler = src
+			}
 		}
 	}
 
@@ -416,7 +419,7 @@ func run(ctx context.Context, manager Manager, config Config) error {
 		}
 	}
 
-	if err := serve(ctx, server, signals, sd.Shutdown); err != nil {
+	if err := serve(ctx, server, signals, sd.Shutdown, pprofHandler); err != nil {
 		if !errors.Is(err, shutdown.ErrShutdown) {
 			cleanupSockets(ctx)
 			return err
@@ -437,7 +440,7 @@ func run(ctx context.Context, manager Manager, config Config) error {
 
 // serve serves the ttrpc API over a unix socket in the current working directory
 // and blocks until the context is canceled
-func serve(ctx context.Context, server *ttrpc.Server, signals chan os.Signal, shutdown func()) error {
+func serve(ctx context.Context, server *ttrpc.Server, signals chan os.Signal, shutdown func(), pprof server) error {
 	dump := make(chan os.Signal, 32)
 	setupDumpStacks(dump)
 
@@ -457,9 +460,9 @@ func serve(ctx context.Context, server *ttrpc.Server, signals chan os.Signal, sh
 		}
 	}()
 
-	if debugFlag {
-		if err := serveDebug(ctx); err != nil {
-			return err
+	if debugFlag && pprof != nil {
+		if err := setupPprof(ctx, pprof); err != nil {
+			log.G(ctx).WithError(err).Warn("Could not setup pprof")
 		}
 	}
 
@@ -478,31 +481,6 @@ func serve(ctx context.Context, server *ttrpc.Server, signals chan os.Signal, sh
 	return reap(ctx, logger, signals)
 }
 
-func serveDebug(ctx context.Context) error {
-	l, err := serveListener(debugSocketFlag, 4)
-	if err != nil {
-		return err
-	}
-	go func() {
-		defer l.Close()
-		m := http.NewServeMux()
-		m.Handle("/debug/vars", expvar.Handler())
-		m.Handle("/debug/pprof/", http.HandlerFunc(pprof.Index))
-		m.Handle("/debug/pprof/cmdline", http.HandlerFunc(pprof.Cmdline))
-		m.Handle("/debug/pprof/profile", http.HandlerFunc(pprof.Profile))
-		m.Handle("/debug/pprof/symbol", http.HandlerFunc(pprof.Symbol))
-		m.Handle("/debug/pprof/trace", http.HandlerFunc(pprof.Trace))
-		srv := &http.Server{
-			Handler:           m,
-			ReadHeaderTimeout: 5 * time.Minute,
-		}
-		if err := srv.Serve(l); err != nil && !errors.Is(err, net.ErrClosed) {
-			log.G(ctx).WithError(err).Fatal("containerd-shim: pprof endpoint failure")
-		}
-	}()
-	return nil
-}
-
 func dumpStacks(logger *log.Entry) {
 	var (
 		buf       []byte
@@ -517,3 +495,22 @@ func dumpStacks(logger *log.Entry) {
 	buf = buf[:stackSize]
 	logger.Infof("=== BEGIN goroutine stack dump ===\n%s\n=== END goroutine stack dump ===", buf)
 }
+
+type server interface {
+	Serve(net.Listener) error
+}
+
+func setupPprof(ctx context.Context, srv server) error {
+	l, err := serveListener(debugSocketFlag, 4)
+	if err != nil {
+		return fmt.Errorf("could not setup pprof listener: %w", err)
+	}
+
+	go func() {
+		if err := srv.Serve(l); err != nil && !errors.Is(err, net.ErrClosed) {
+			log.G(ctx).WithError(err).Fatal("containerd-shim: pprof endpoint failure")
+		}
+	}()
+
+	return nil
+}

plugins/types.go

@@ -73,6 +73,8 @@ const (
 	CRIServicePlugin plugin.Type = "io.containerd.cri.v1"
 	// ShimPlugin implements a shim service
 	ShimPlugin plugin.Type = "io.containerd.shim.v1"
+	// HTTPHandler implements an http handler
+	HTTPHandler plugin.Type = "io.containerd.http.v1"
 )
 
 const (