Ensure Tracer.close() properly flushes finished but unsent spans (#294)

* assigning to Reporter._stopped in _flush() instead of close()
avoids dropping those spans passed to report_span just _prior_ to
Reporter.close() for which _report_span_from_ioloop will execute only
*afterwards*; this way those scheduled callbacks will get a chance to
run before _flush stops the reporter and those pending spans make it
into the queue before the reporter shuts down.

Signed-off-by: obataku <[email protected]>

Co-authored-by: Yuri Shkuro <[email protected]>

Author: obataku

jaeger_client/reporter.py

@@ -215,13 +215,13 @@ def close(self):
         Ensure that all spans from the queue are submitted.
         Returns Future that will be completed once the queue is empty.
         """
-        with self.stop_lock:
-            self.stopped = True
-
         return ioloop_util.submit(self._flush, io_loop=self.io_loop)
 
     @tornado.gen.coroutine
     def _flush(self):
+        # stopping here ensures we don't lose spans from pending _report_span_from_ioloop callbacks
+        with self.stop_lock:
+            self.stopped = True
         yield self.queue.put(self.stop)
         yield self.queue.join()