Add Systemd watchdog

systemd/systemd.go

@@ -0,0 +1,74 @@
+// Copyright 2021 Frédéric Guillot. All rights reserved.
+// Use of this source code is governed by the Apache 2.0
+// license that can be found in the LICENSE file.
+
+package systemd // import "miniflux.app/systemd"
+
+import (
+	"fmt"
+	"net"
+	"os"
+	"strconv"
+	"time"
+)
+
+const (
+	// SdNotifyReady tells the service manager that service startup is
+	// finished, or the service finished loading its configuration.
+	// https://www.freedesktop.org/software/systemd/man/sd_notify.html#READY=1
+	SdNotifyReady = "READY=1"
+
+	// SdNotifyWatchdog the service manager to update the watchdog timestamp.
+	// https://www.freedesktop.org/software/systemd/man/sd_notify.html#WATCHDOG=1
+	SdNotifyWatchdog = "WATCHDOG=1"
+)
+
+// HasNotifySocket checks if the process is supervised by Systemd and has the notify socket.
+func HasNotifySocket() bool {
+	return os.Getenv("NOTIFY_SOCKET") != ""
+}
+
+// HasSystemdWatchdog checks if the watchdog is configured in Systemd unit file.
+func HasSystemdWatchdog() bool {
+	return os.Getenv("WATCHDOG_USEC") != ""
+}
+
+// WatchdogInterval returns the watchdog interval configured in systemd unit file.
+func WatchdogInterval() (time.Duration, error) {
+	s, err := strconv.Atoi(os.Getenv("WATCHDOG_USEC"))
+	if err != nil {
+		return 0, fmt.Errorf(`systemd: error converting WATCHDOG_USEC: %v`, err)
+	}
+
+	if s <= 0 {
+		return 0, fmt.Errorf(`systemd: error WATCHDOG_USEC must be a positive number`)
+	}
+
+	return time.Duration(s) * time.Microsecond, nil
+}
+
+// SdNotify sends a message to systemd using the sd_notify protocol.
+// See https://www.freedesktop.org/software/systemd/man/sd_notify.html.
+func SdNotify(state string) error {
+	addr := &net.UnixAddr{
+		Net:  "unixgram",
+		Name: os.Getenv("NOTIFY_SOCKET"),
+	}
+
+	if addr.Name == "" {
+		// We're not running under systemd (NOTIFY_SOCKET is not set).
+		return nil
+	}
+
+	conn, err := net.DialUnix(addr.Net, nil, addr)
+	if err != nil {
+		return err
+	}
+	defer conn.Close()
+
+	if _, err = conn.Write([]byte(state)); err != nil {
+		return err
+	}
+
+	return nil
+}