fix(inputs.systemd_units): Reconnect if connection is lost (#15129)

plugins/inputs/systemd_units/systemd_units_linux.go

@@ -183,9 +183,19 @@ func (s *SystemdUnits) Stop() {
 	if s.client != nil && s.client.Connected() {
 		s.client.Close()
 	}
+	s.client = nil
 }
 
 func (s *SystemdUnits) Gather(acc telegraf.Accumulator) error {
+	// Reconnect in case the connection was lost
+	if !s.client.Connected() {
+		s.Log.Debug("Connection to systemd daemon lost, trying to reconnect...")
+		s.Stop()
+		if err := s.Start(acc); err != nil {
+			return err
+		}
+	}
+
 	ctx, cancel := context.WithTimeout(context.Background(), time.Duration(s.Timeout))
 	defer cancel()
 

plugins/inputs/systemd_units/systemd_units_test.go

@@ -209,6 +209,7 @@ func TestListFiles(t *testing.T) {
 			plugin := &SystemdUnits{
 				Pattern: "examp*",
 				Timeout: config.Duration(time.Second),
+				Log:     testutil.Logger{},
 			}
 			require.NoError(t, plugin.Init())
 
@@ -522,6 +523,7 @@ func TestShow(t *testing.T) {
 				Pattern: "examp*",
 				Details: true,
 				Timeout: config.Duration(time.Second),
+				Log:     testutil.Logger{},
 			}
 			require.NoError(t, plugin.Init())
 
@@ -715,6 +717,7 @@ func TestMultiInstance(t *testing.T) {
 			plugin := &SystemdUnits{
 				Pattern: tt.pattern,
 				Timeout: config.Duration(time.Second),
+				Log:     testutil.Logger{},
 			}
 			require.NoError(t, plugin.Init())
 
@@ -825,7 +828,7 @@ func (c *fakeClient) fixPropertyTypes() {
 }
 
 func (c *fakeClient) Connected() bool {
-	return !c.connected
+	return c.connected
 }
 
 func (c *fakeClient) Close() {