Merge pull request #29863 from ncdc/journald-logdriver-drain-one-more-time-after-follow-ends

journald logs: drain 1 more time at container exit

daemon/logger/journald/read.go

@@ -245,20 +245,28 @@ func (s *journald) followJournal(logWatcher *logger.LogWatcher, config logger.Re
 	s.readers.mu.Lock()
 	s.readers.readers[logWatcher] = logWatcher
 	s.readers.mu.Unlock()
+
 	go func() {
-		// Keep copying journal data out until we're notified to stop
-		// or we hit an error.
-		status := C.wait_for_data_cancelable(j, pfd[0])
-		for status == 1 {
+		for {
+			// Keep copying journal data out until we're notified to stop
+			// or we hit an error.
+			status := C.wait_for_data_cancelable(j, pfd[0])
+			if status < 0 {
+				cerrstr := C.strerror(C.int(-status))
+				errstr := C.GoString(cerrstr)
+				fmtstr := "error %q while attempting to follow journal for container %q"
+				logrus.Errorf(fmtstr, errstr, s.vars["CONTAINER_ID_FULL"])
+				break
+			}
+
 			cursor = s.drainJournal(logWatcher, config, j, cursor)
-			status = C.wait_for_data_cancelable(j, pfd[0])
-		}
-		if status < 0 {
-			cerrstr := C.strerror(C.int(-status))
-			errstr := C.GoString(cerrstr)
-			fmtstr := "error %q while attempting to follow journal for container %q"
-			logrus.Errorf(fmtstr, errstr, s.vars["CONTAINER_ID_FULL"])
+
+			if status != 1 {
+				// We were notified to stop
+				break
+			}
 		}
+
 		// Clean up.
 		C.close(pfd[0])
 		s.readers.mu.Lock()
@@ -267,6 +275,7 @@ func (s *journald) followJournal(logWatcher *logger.LogWatcher, config logger.Re
 		C.sd_journal_close(j)
 		close(logWatcher.Msg)
 	}()
+
 	// Wait until we're told to stop.
 	select {
 	case <-logWatcher.WatchClose():