cirq-ionq: Retry non-standard cloudflare errors (quantumlib#5237)

Author: Cynocracy

cirq-ionq/cirq_ionq/ionq_client.py

@@ -24,17 +24,24 @@
 import cirq_ionq
 from cirq_ionq import ionq_exceptions
 
+RETRIABLE_STATUS_CODES = {
+    requests.codes.internal_server_error,
+    requests.codes.service_unavailable,
+}
+
+
+def _is_retriable(code):
+    # Handle 52x responses from cloudflare.
+    # See https://support.cloudflare.com/hc/en-us/articles/115003011431/
+    return code in RETRIABLE_STATUS_CODES or (code >= 520 and code <= 530)
+
 
 class _IonQClient:
     """Handles calls to IonQ's API.
 
     Users should not instantiate this themselves, but instead should use `cirq_ionq.Service`.
     """
 
-    RETRIABLE_STATUS_CODES = {
-        requests.codes.internal_server_error,
-        requests.codes.service_unavailable,
-    }
     SUPPORTED_TARGETS = {'qpu', 'simulator'}
     SUPPORTED_VERSIONS = {
         'v0.1',
@@ -294,7 +301,7 @@ def _make_request(self, request: Callable[[], requests.Response]) -> requests.Re
                     raise ionq_exceptions.IonQNotFoundException(
                         'IonQ could not find requested resource.'
                     )
-                if response.status_code not in self.RETRIABLE_STATUS_CODES:
+                if not _is_retriable(response.status_code):
                     raise ionq_exceptions.IonQException(
                         'Non-retry-able error making request to IonQ API. '
                         f'Status: {response.status_code} '

cirq-ionq/cirq_ionq/ionq_client_test.py

@@ -757,3 +757,18 @@ def test_ionq_client_list_calibrations_retry(mock_get):
     )
     client.list_calibrations()
     assert mock_get.call_count == 2
+
+
+@mock.patch('requests.get')
+def test_ionq_client_list_calibrations_retry_nonstandard_error(mock_get):
+    response1 = mock.MagicMock()
+    response2 = mock.MagicMock()
+    mock_get.side_effect = [response1, response2]
+    response1.ok = False
+    response1.status_code = 524
+    response2.ok = True
+    client = ionq.ionq_client._IonQClient(
+        remote_host='http://example.com', api_key='to_my_heart', default_target='simulator'
+    )
+    client.list_calibrations()
+    assert mock_get.call_count == 2