Retry watch if request expires.

Author: mitar

Diff for: watch/watch.py

@@ -91,7 +91,7 @@ def unmarshal_event(self, data, return_type):
         except ValueError:
             return data
         js['raw_object'] = js['object']
-        if return_type:
+        if return_type and js['type'] != 'ERROR':
             obj = SimpleNamespace(data=json.dumps(js['raw_object']))
             js['object'] = self._api_client.deserialize(obj, return_type)
             if hasattr(js['object'], 'metadata'):
@@ -107,6 +107,14 @@ def unmarshal_event(self, data, return_type):
     def stream(self, func, *args, **kwargs):
         """Watch an API resource and stream the result back via a generator.
 
+        Note that watching an API resource can expire. The method tries to
+        resume automatically from the last result, but if that last result
+        is too old as well, an `ApiException` exception will be thrown with
+        ``code`` 410. In that case you have to recover yourself, probably
+        by listing the API resource to obtain the latest state and then
+        watching from that state on by setting ``resource_version`` to
+        one returned from listing.
+
         :param func: The API function pointer. Any parameter to the function
                      can be passed after this parameter.
 
@@ -138,11 +146,26 @@ def stream(self, func, *args, **kwargs):
             self.resource_version = kwargs['resource_version']
 
         timeouts = ('timeout_seconds' in kwargs)
+        retry_after_410 = False
         while True:
             resp = func(*args, **kwargs)
             try:
                 for line in iter_resp_lines(resp):
-                    yield self.unmarshal_event(line, return_type)
+                    event = self.unmarshal_event(line, return_type)
+                    if isinstance(event, dict) and event['type'] == 'ERROR':
+                        obj = event['raw_object']
+                        # Current request expired, let's retry,
+                        # but only if we have not already retried.
+                        if not retry_after_410 and obj['code'] == 410:
+                            retry_after_410 = True
+                            break
+                        else:
+                            reason = "%s: %s" % (obj['reason'], obj['message'])
+                            raise client.rest.ApiException(status=obj['code'],
+                                                           reason=reason)
+                    else:
+                        retry_after_410 = False
+                        yield event
                     if self._stop:
                         break
             finally:

Diff for: watch/watch_test.py

@@ -18,6 +18,8 @@
 
 from mock import Mock, call
 
+from kubernetes import client
+
 from .watch import Watch
 
 
@@ -275,6 +277,31 @@ def test_watch_with_exception(self):
         fake_resp.close.assert_called_once()
         fake_resp.release_conn.assert_called_once()
 
+    def test_watch_with_error_event(self):
+        fake_resp = Mock()
+        fake_resp.close = Mock()
+        fake_resp.release_conn = Mock()
+        fake_resp.read_chunked = Mock(
+            return_value=[
+                '{"type": "ERROR", "object": {"code": 410, '
+                '"reason": "Gone", "message": "error message"}}\n'])
+
+        fake_api = Mock()
+        fake_api.get_thing = Mock(return_value=fake_resp)
+
+        w = Watch()
+        try:
+            for _ in w.stream(fake_api.get_thing):
+                self.fail(self, "Should fail with ApiException.")
+        except client.rest.ApiException:
+            pass
+
+        fake_api.get_thing.assert_called_once_with(
+            _preload_content=False, watch=True)
+        fake_resp.read_chunked.assert_called_once_with(decode_content=False)
+        fake_resp.close.assert_called_once()
+        fake_resp.release_conn.assert_called_once()
+
 
 if __name__ == '__main__':
     unittest.main()