Mitigate issues with expired HANA tokens (#529)

* Pad expired tokens by 30s to renew before expiration
Handle expired token responses by renewing token and re-requesting backend

* Simplify expiration calculation for readability
Add test coverage for token refresh upon request

---------

Co-authored-by: Daniel McKnight <daniel@neon.ai>

neon_utils/hana_utils.py

@@ -156,7 +156,7 @@ def request_backend(endpoint: str, request_data: dict,
         _client_config = {}
         _headers = {}
     _init_client(server_url)
-    if time() >= _client_config.get("expiration", 0):
+    if _client_config.get("expiration", 0) - time() < 30:
         try:
             _refresh_token(server_url)
         except ServerException as e:
@@ -172,4 +172,16 @@ def request_backend(endpoint: str, request_data: dict,
         return resp.json()
 
     else:
+        try:
+            error = resp.json()["detail"]
+            # Token is actually expired, refresh and retry
+            if error == "Invalid or expired token.":
+                LOG.warning(f"Token is expired. time={time()}|"
+                            f"expiration={_client_config.get('expiration')}")
+                _refresh_token(server_url)
+                resp = requests.post(**request_kwargs)
+                if resp.ok:
+                    return resp.json()
+        except Exception as e:
+            LOG.error(e)
         raise ServerException(f"Error response {resp.status_code}: {resp.text}")

tests/hana_util_tests.py

@@ -25,10 +25,13 @@
 # LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 # NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 # SOFTWARE,  EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
 import json
 import unittest
+
 from os import remove
 from os.path import join, dirname, isfile
+from time import time
 from unittest.mock import patch
 
 
@@ -70,6 +73,28 @@ def test_request_backend(self, config_path):
         self.assertIsInstance(resp['answer'], str)
         # TODO: Test invalid route, invalid request data
 
+    @patch("neon_utils.hana_utils._get_client_config_path")
+    @patch("neon_utils.hana_utils._refresh_token")
+    def test_request_backend_refresh_token(self, refresh_token, config_path):
+        config_path.return_value = self.test_path
+
+        import neon_utils.hana_utils
+        from neon_utils.hana_utils import request_backend
+        neon_utils.hana_utils.set_default_backend_url(self.test_server)
+        neon_utils.hana_utils._init_client(self.test_server)
+        real_client_config = neon_utils.hana_utils._client_config
+        neon_utils.hana_utils._client_config['expiration'] = time() + 29
+        neon_utils.hana_utils._refresh_token = refresh_token
+        resp = request_backend("/neon/get_response",
+                               {"lang_code": "en-us",
+                                "utterance": "how are you",
+                                "user_profile": {}}, self.test_server)
+        self.assertEqual(resp['lang_code'], "en-us")
+        self.assertIsInstance(resp['answer'], str)
+        refresh_token.assert_called_once_with(self.test_server)
+
+        neon_utils.hana_utils._client_config = real_client_config
+
     @patch("neon_utils.hana_utils._get_client_config_path")
     def test_00_get_token(self, config_path):
         config_path.return_value = self.test_path