Merge pull request #133 from mitar/retry-watch

Retry expired watches

watch/watch.py

@@ -12,6 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import http
 import json
 import pydoc
 
@@ -86,7 +87,7 @@ class Watch(object):
     def unmarshal_event(self, data, return_type):
         js = json.loads(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'):
@@ -102,6 +103,14 @@ class Watch(object):
     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 once 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.
 
@@ -134,6 +143,7 @@ class Watch(object):
             self.resource_version = kwargs['resource_version']
 
         timeouts = ('timeout_seconds' in kwargs)
+        retry_after_410 = False
         while True:
             resp = func(*args, **kwargs)
             try:
@@ -141,7 +151,23 @@ class Watch(object):
                     # unmarshal when we are receiving events from watch,
                     # return raw string when we are streaming log
                     if watch_arg == "watch":
-                        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'] == http.HTTPStatus.GONE:
+                                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
                     else:
                         yield line
                     if self._stop:

watch/watch_test.py

@@ -16,6 +16,8 @@ import unittest
 
 from mock import Mock, call
 
+from kubernetes import client
+
 from .watch import Watch
 
 
@@ -273,6 +275,31 @@ class WatchTests(unittest.TestCase):
         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()