feat(proxy): add sd_notify support

proxy/lib/snowflake.go

@@ -822,6 +822,8 @@ func (sf *SnowflakeProxy) Start() error {
 	}
 	tokens = newTokens(sf.Capacity)
 
+	sdnotifyStatus("Checking NAT type...")
+
 	err = sf.checkNATType(config, sf.NATProbeURL)
 	if err != nil {
 		// non-fatal error. Log it and continue
@@ -830,6 +832,9 @@ func (sf *SnowflakeProxy) Start() error {
 	}
 	sf.EventDispatcher.OnNewSnowflakeEvent(event.EventOnCurrentNATTypeDetermined{CurNATType: getCurrentNATType()})
 
+	sdnotifyStatus(fmt.Sprintf("NAT type: %s", getCurrentNATType()))
+	sdnotifyReady()
+
 	NatRetestTask := task.Periodic{
 		Interval: sf.NATTypeMeasurementInterval,
 		Execute: func() error {
@@ -846,6 +851,16 @@ func (sf *SnowflakeProxy) Start() error {
 		defer NatRetestTask.Close()
 	}
 
+	WatchdogTask := task.Periodic{
+		Interval: 5 * time.Minute,
+		Execute: func() error {
+			sdnotifyWatchdog()
+			return nil
+		},
+	}
+	WatchdogTask.Start()
+	defer WatchdogTask.Close()
+
 	ticker := time.NewTicker(sf.PollInterval)
 	defer ticker.Stop()
 
@@ -864,6 +879,7 @@ func (sf *SnowflakeProxy) Start() error {
 
 // Stop closes all existing connections and shuts down the Snowflake.
 func (sf *SnowflakeProxy) Stop() {
+	sdnotifyStopping()
 	close(sf.shutdown)
 }
 

proxy/lib/systemd.go

@@ -0,0 +1,23 @@
+package snowflake_proxy
+
+import (
+	"fmt"
+
+	sdnotify "github.com/coreos/go-systemd/v22/daemon"
+)
+
+func sdnotifyReady() {
+	sdnotify.SdNotify(false, sdnotify.SdNotifyReady)
+}
+
+func sdnotifyStopping() {
+	sdnotify.SdNotify(false, sdnotify.SdNotifyStopping)
+}
+
+func sdnotifyStatus(status string) {
+	sdnotify.SdNotify(false, fmt.Sprintf("STATUS=%s", status))
+}
+
+func sdnotifyWatchdog() {
+	sdnotify.SdNotify(false, sdnotify.SdNotifyWatchdog)
+}