Support NOTIFY_SOCKET

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

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
+}