Add support for systemd sd_notify

cmd/apiary.go

@@ -8,6 +8,7 @@ import (
 	"os/signal"
 	"time"
 
+	"github.com/coreos/go-systemd/daemon"
 	sshlib "github.com/gliderlabs/ssh"
 	"github.com/urfave/cli/v2"
 	"github.uio.no/torjus/apiary"
@@ -165,6 +166,56 @@ func ActionServe(c *cli.Context) error {
 		}
 	}()
 
+	// If run by systemd, enable watchdog and notify ready
+	go func() {
+		notifyCtx, cancel := context.WithCancel(rootCtx)
+		defer cancel()
+
+		_, ok := os.LookupEnv("NOTIFY_SOCKET")
+		if !ok {
+			return
+		}
+		loggers.rootLogger.Info("Systemd notify socket detected. Sending ready and enabling watchdog.")
+		ok, err := daemon.SdNotify(false, daemon.SdNotifyReady)
+		if !ok {
+			loggers.rootLogger.Info("Systemd notify not enabled.")
+			return
+		}
+		if err != nil {
+			loggers.rootLogger.Warnw("Unable to connect to NOTIFY_SOCKET.", "error", err)
+			return
+		}
+		loggers.rootLogger.Debug("Sent READY=1 to NOTIFY_SOCKET.")
+
+		if _, err := daemon.SdNotify(false, "WATCHDOG_USEC=10000000"); err != nil {
+			loggers.rootLogger.Warnw("Unable to connect to NOTIFY_SOCKET to set watchdog timeout.", "error", err)
+			return
+		}
+		loggers.rootLogger.Debug("Sent WATCHDOG_USEC=10000000 to NOTIFY_SOCKET.")
+		if _, err := daemon.SdNotify(false, "WATCHDOG_USEC=10000000"); err != nil {
+			loggers.rootLogger.Warnw("Unable to connect to NOTIFY_SOCKET to set watchdog timeout.", "error", err)
+			return
+		}
+		timeout, err := daemon.SdWatchdogEnabled(false)
+		if err != nil {
+			loggers.rootLogger.Warnw("Unable to connect to NOTIFY_SOCKET to get watchdog timeout.", "error", err)
+			return
+		}
+		ticker := time.NewTicker(timeout / 2)
+		for {
+			healthy := s.IsHealthy()
+			select {
+			case <-ticker.C:
+				if healthy == nil {
+					daemon.SdNotify(false, daemon.SdNotifyWatchdog)
+				}
+			case <-notifyCtx.Done():
+				loggers.rootLogger.Debugw("Notify context cancelled.")
+				return
+			}
+		}
+	}()
+
 	go func() {
 		<-serversCtx.Done()