Remove reaper from containerd daemon

This allows other packages and plugins to easily exec things without
racing with the reaper.

The reaper is mostly needed in the shim but can be removed in containerd
in favor of the `exec.Cmd` apis

Signed-off-by: Michael Crosby <crosbymichael@gmail.com>

cmd/containerd/config_linux.go

@@ -12,7 +12,6 @@ func defaultConfig() *server.Config {
 		GRPC: server.GRPCConfig{
 			Address: defaults.DefaultAddress,
 		},
-		NoSubreaper: false,
 		Debug: server.Debug{
 			Level:   "info",
 			Address: defaults.DefaultDebugAddress,

cmd/containerd/main_unix.go

@@ -11,7 +11,6 @@ import (
 	"golang.org/x/sys/unix"
 
 	"github.com/containerd/containerd/log"
-	"github.com/containerd/containerd/reaper"
 	"github.com/containerd/containerd/server"
 )
 
@@ -21,7 +20,6 @@ var handledSignals = []os.Signal{
 	unix.SIGTERM,
 	unix.SIGINT,
 	unix.SIGUSR1,
-	unix.SIGCHLD,
 	unix.SIGPIPE,
 }
 
@@ -36,10 +34,6 @@ func handleSignals(ctx context.Context, signals chan os.Signal, serverC chan *se
 			case s := <-signals:
 				log.G(ctx).WithField("signal", s).Debug("received signal")
 				switch s {
-				case unix.SIGCHLD:
-					if err := reaper.Reap(); err != nil {
-						log.G(ctx).WithError(err).Error("reap containerd processes")
-					}
 				case unix.SIGUSR1:
 					dumpStacks()
 				case unix.SIGPIPE:

linux/runtime.go

@@ -26,9 +26,7 @@ import (
 	"github.com/containerd/containerd/namespaces"
 	"github.com/containerd/containerd/platforms"
 	"github.com/containerd/containerd/plugin"
-	"github.com/containerd/containerd/reaper"
 	"github.com/containerd/containerd/runtime"
-	"github.com/containerd/containerd/sys"
 	runc "github.com/containerd/go-runc"
 	"github.com/containerd/typeurl"
 	ptypes "github.com/gogo/protobuf/types"
@@ -159,9 +157,6 @@ func (r *Runtime) Create(ctx context.Context, id string, opts runtime.CreateOpts
 		return nil, err
 	}
 
-	ec := reaper.Default.Subscribe()
-	defer reaper.Default.Unsubscribe(ec)
-
 	bundle, err := newBundle(id,
 		filepath.Join(r.state, namespace),
 		filepath.Join(r.root, namespace),
@@ -206,7 +201,7 @@ func (r *Runtime) Create(ctx context.Context, id string, opts runtime.CreateOpts
 				"id":        id,
 				"namespace": namespace,
 			}).Warn("cleaning up after killed shim")
-			err = r.cleanupAfterDeadShim(context.Background(), bundle, namespace, id, lc.pid, ec)
+			err = r.cleanupAfterDeadShim(context.Background(), bundle, namespace, id, lc.pid)
 			if err == nil {
 				r.tasks.Delete(ctx, lc)
 			} else {
@@ -313,7 +308,7 @@ func (r *Runtime) Delete(ctx context.Context, c runtime.Task) (*runtime.Exit, er
 
 	rsp, err := lc.shim.Delete(ctx, empty)
 	if err != nil {
-		if cerr := r.cleanupAfterDeadShim(ctx, bundle, namespace, c.ID(), lc.pid, nil); cerr != nil {
+		if cerr := r.cleanupAfterDeadShim(ctx, bundle, namespace, c.ID(), lc.pid); cerr != nil {
 			log.G(ctx).WithError(err).Error("unable to cleanup task")
 		}
 		return nil, errdefs.FromGRPC(err)
@@ -394,7 +389,7 @@ func (r *Runtime) loadTasks(ctx context.Context, ns string) ([]*Task, error) {
 				"id":        id,
 				"namespace": ns,
 			}).Error("connecting to shim")
-			err := r.cleanupAfterDeadShim(ctx, bundle, ns, id, pid, nil)
+			err := r.cleanupAfterDeadShim(ctx, bundle, ns, id, pid)
 			if err != nil {
 				log.G(ctx).WithError(err).WithField("bundle", bundle.path).
 					Error("cleaning up after dead shim")
@@ -419,7 +414,7 @@ func (r *Runtime) loadTasks(ctx context.Context, ns string) ([]*Task, error) {
 	return o, nil
 }
 
-func (r *Runtime) cleanupAfterDeadShim(ctx context.Context, bundle *bundle, ns, id string, pid int, ec chan runc.Exit) error {
+func (r *Runtime) cleanupAfterDeadShim(ctx context.Context, bundle *bundle, ns, id string, pid int) error {
 	ctx = namespaces.WithNamespace(ctx, ns)
 	if err := r.terminate(ctx, bundle, ns, id); err != nil {
 		if r.config.ShimDebug {
@@ -428,17 +423,6 @@ func (r *Runtime) cleanupAfterDeadShim(ctx context.Context, bundle *bundle, ns,
 		log.G(ctx).WithError(err).Warn("failed to terminate task")
 	}
 
-	if ec != nil {
-		// if sub-reaper is set, reap our new child
-		if v, err := sys.GetSubreaper(); err == nil && v == 1 {
-			for e := range ec {
-				if e.Pid == pid {
-					break
-				}
-			}
-		}
-	}
-
 	// Notify Client
 	exitedAt := time.Now().UTC()
 	r.events.Publish(ctx, runtime.TaskExitEventTopic, &eventstypes.TaskExit{

linux/shim/client/client.go

@@ -23,7 +23,6 @@ import (
 	"github.com/containerd/containerd/linux/shim"
 	shimapi "github.com/containerd/containerd/linux/shim/v1"
 	"github.com/containerd/containerd/log"
-	"github.com/containerd/containerd/reaper"
 	"github.com/containerd/containerd/sys"
 	ptypes "github.com/gogo/protobuf/types"
 )
@@ -51,8 +50,7 @@ func WithStart(binary, address, daemonAddress, cgroup string, debug bool, exitHa
 		if err != nil {
 			return nil, nil, err
 		}
-		ec, err := reaper.Default.Start(cmd)
-		if err != nil {
+		if err := cmd.Start(); err != nil {
 			return nil, nil, errors.Wrapf(err, "failed to start shim")
 		}
 		defer func() {
@@ -61,7 +59,7 @@ func WithStart(binary, address, daemonAddress, cgroup string, debug bool, exitHa
 			}
 		}()
 		go func() {
-			reaper.Default.Wait(cmd, ec)
+			cmd.Wait()
 			exitHandler()
 		}()
 		log.G(ctx).WithFields(logrus.Fields{

server/config.go

@@ -23,8 +23,6 @@ type Config struct {
 	Metrics MetricsConfig `toml:"metrics"`
 	// Plugins provides plugin specific configuration for the initialization of a plugin
 	Plugins map[string]toml.Primitive `toml:"plugins"`
-	// NoSubreaper disables containerd as a subreaper
-	NoSubreaper bool `toml:"no_subreaper"`
 	// OOMScore adjust the containerd's oom score
 	OOMScore int `toml:"oom_score"`
 	// Cgroup specifies cgroup information for the containerd daemon process

server/server_linux.go

@@ -12,12 +12,6 @@ import (
 
 // apply sets config settings on the server process
 func apply(ctx context.Context, config *Config) error {
-	if !config.NoSubreaper {
-		log.G(ctx).Info("setting subreaper...")
-		if err := sys.SetSubreaper(1); err != nil {
-			return err
-		}
-	}
 	if config.OOMScore != 0 {
 		log.G(ctx).Debugf("changing OOM score to %d", config.OOMScore)
 		if err := sys.SetOOMScore(os.Getpid(), config.OOMScore); err != nil {