Support NOTIFY_SOCKET

Signed-off-by: Maksym Pavlenko <makpav@amazon.com>

cmd/containerd/command/main.go

@@ -227,6 +227,10 @@ can be used and modified as necessary as a custom configuration.`
 		}
 		serve(ctx, l, server.ServeGRPC)
 
+		if err := notifyReady(ctx); err != nil {
+			log.G(ctx).WithError(err).Warn("notify ready failed")
+		}
+
 		log.G(ctx).Infof("containerd successfully booted in %fs", time.Since(start).Seconds())
 		<-done
 		return nil

cmd/containerd/command/main_unix.go

@@ -52,6 +52,10 @@ func handleSignals(ctx context.Context, signals chan os.Signal, serverC chan *se
 				case unix.SIGPIPE:
 					continue
 				default:
+					if err := notifyStopping(ctx); err != nil {
+						log.G(ctx).WithError(err).Error("notify stopping failed")
+					}
+
 					if server == nil {
 						close(done)
 						return

cmd/containerd/command/main_windows.go

@@ -50,6 +50,11 @@ func handleSignals(ctx context.Context, signals chan os.Signal, serverC chan *se
 				server = s
 			case s := <-signals:
 				log.G(ctx).WithField("signal", s).Debug("received signal")
+
+				if err := notifyStopping(ctx); err != nil {
+					log.G(ctx).WithError(err).Error("notify stopping failed")
+				}
+
 				if server == nil {
 					close(done)
 					return

cmd/containerd/command/notify_linux.go

@@ -0,0 +1,52 @@
+// +build linux
+
+/*
+   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 command
+
+import (
+	"context"
+	"os"
+
+	sd "github.com/coreos/go-systemd/v22/daemon"
+
+	"github.com/containerd/containerd/log"
+)
+
+// notifyReady notifies systemd that the daemon is ready to serve requests
+func notifyReady(ctx context.Context) error {
+	return sdNotify(ctx, sd.SdNotifyReady)
+}
+
+// notifyStopping notifies systemd that the daemon is about to be stopped
+func notifyStopping(ctx context.Context) error {
+	return sdNotify(ctx, sd.SdNotifyStopping)
+}
+
+func sdNotify(ctx context.Context, state string) error {
+	if os.Getenv("NOTIFY_SOCKET") != "" {
+		notified, err := sd.SdNotify(false, state)
+		log.G(ctx).
+			WithError(err).
+			WithField("notified", notified).
+			WithField("state", state).
+			Debug("sd notification")
+		return err
+	}
+
+	return nil
+}

cmd/containerd/command/notify_unsupported.go

@@ -0,0 +1,31 @@
+// +build !linux
+
+/*
+   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 command
+
+import (
+	"context"
+)
+
+func notifyReady(ctx context.Context) error {
+	return nil
+}
+
+func notifyStopping(ctx context.Context) error {
+	return nil
+}

containerd.service

@@ -7,6 +7,7 @@ After=network.target local-fs.target
 ExecStartPre=-/sbin/modprobe overlay
 ExecStart=/usr/local/bin/containerd
 
+Type=notify
 Delegate=yes
 KillMode=process
 Restart=always

vendor/github.com/coreos/go-systemd/v22/daemon/sdnotify.go

@@ -0,0 +1,84 @@
+// Copyright 2014 Docker, Inc.
+// Copyright 2015-2018 CoreOS, Inc.
+//
+// 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 daemon provides a Go implementation of the sd_notify protocol.
+// It can be used to inform systemd of service start-up completion, watchdog
+// events, and other status changes.
+//
+// https://www.freedesktop.org/software/systemd/man/sd_notify.html#Description
+package daemon
+
+import (
+	"net"
+	"os"
+)
+
+const (
+	// SdNotifyReady tells the service manager that service startup is finished
+	// or the service finished loading its configuration.
+	SdNotifyReady = "READY=1"
+
+	// SdNotifyStopping tells the service manager that the service is beginning
+	// its shutdown.
+	SdNotifyStopping = "STOPPING=1"
+
+	// SdNotifyReloading tells the service manager that this service is
+	// reloading its configuration. Note that you must call SdNotifyReady when
+	// it completed reloading.
+	SdNotifyReloading = "RELOADING=1"
+
+	// SdNotifyWatchdog tells the service manager to update the watchdog
+	// timestamp for the service.
+	SdNotifyWatchdog = "WATCHDOG=1"
+)
+
+// SdNotify sends a message to the init daemon. It is common to ignore the error.
+// If `unsetEnvironment` is true, the environment variable `NOTIFY_SOCKET`
+// will be unconditionally unset.
+//
+// It returns one of the following:
+// (false, nil) - notification not supported (i.e. NOTIFY_SOCKET is unset)
+// (false, err) - notification supported, but failure happened (e.g. error connecting to NOTIFY_SOCKET or while sending data)
+// (true, nil) - notification supported, data has been sent
+func SdNotify(unsetEnvironment bool, state string) (bool, error) {
+	socketAddr := &net.UnixAddr{
+		Name: os.Getenv("NOTIFY_SOCKET"),
+		Net:  "unixgram",
+	}
+
+	// NOTIFY_SOCKET not set
+	if socketAddr.Name == "" {
+		return false, nil
+	}
+
+	if unsetEnvironment {
+		if err := os.Unsetenv("NOTIFY_SOCKET"); err != nil {
+			return false, err
+		}
+	}
+
+	conn, err := net.DialUnix(socketAddr.Net, nil, socketAddr)
+	// Error connecting to NOTIFY_SOCKET
+	if err != nil {
+		return false, err
+	}
+	defer conn.Close()
+
+	if _, err = conn.Write([]byte(state)); err != nil {
+		return false, err
+	}
+	return true, nil
+}

vendor/github.com/coreos/go-systemd/v22/daemon/watchdog.go

@@ -0,0 +1,73 @@
+// Copyright 2016 CoreOS, Inc.
+//
+// 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 daemon
+
+import (
+	"fmt"
+	"os"
+	"strconv"
+	"time"
+)
+
+// SdWatchdogEnabled returns watchdog information for a service.
+// Processes should call daemon.SdNotify(false, daemon.SdNotifyWatchdog) every
+// time / 2.
+// If `unsetEnvironment` is true, the environment variables `WATCHDOG_USEC` and
+// `WATCHDOG_PID` will be unconditionally unset.
+//
+// It returns one of the following:
+// (0, nil) - watchdog isn't enabled or we aren't the watched PID.
+// (0, err) - an error happened (e.g. error converting time).
+// (time, nil) - watchdog is enabled and we can send ping.
+//   time is delay before inactive service will be killed.
+func SdWatchdogEnabled(unsetEnvironment bool) (time.Duration, error) {
+	wusec := os.Getenv("WATCHDOG_USEC")
+	wpid := os.Getenv("WATCHDOG_PID")
+	if unsetEnvironment {
+		wusecErr := os.Unsetenv("WATCHDOG_USEC")
+		wpidErr := os.Unsetenv("WATCHDOG_PID")
+		if wusecErr != nil {
+			return 0, wusecErr
+		}
+		if wpidErr != nil {
+			return 0, wpidErr
+		}
+	}
+
+	if wusec == "" {
+		return 0, nil
+	}
+	s, err := strconv.Atoi(wusec)
+	if err != nil {
+		return 0, fmt.Errorf("error converting WATCHDOG_USEC: %s", err)
+	}
+	if s <= 0 {
+		return 0, fmt.Errorf("error WATCHDOG_USEC must be a positive number")
+	}
+	interval := time.Duration(s) * time.Microsecond
+
+	if wpid == "" {
+		return interval, nil
+	}
+	p, err := strconv.Atoi(wpid)
+	if err != nil {
+		return 0, fmt.Errorf("error converting WATCHDOG_PID: %s", err)
+	}
+	if os.Getpid() != p {
+		return 0, nil
+	}
+
+	return interval, nil
+}