Repository: jupyterhub/oauthenticator
Issue category: Performance Issue

Issue:
The google authenticator's calls to check groups is done sync, can it be made async?
Quickly written, I can fill this in in more detail later.


Hints:

Patch:
diff --git a/oauthenticator/google.py b/oauthenticator/google.py
index f06f6aca..28b76d48 100644
--- a/oauthenticator/google.py
+++ b/oauthenticator/google.py
@@ -14,6 +14,7 @@
 
 class GoogleOAuthenticator(OAuthenticator, GoogleOAuth2Mixin):
     user_auth_state_key = "google_user"
+    _service_credentials = {}
 
     @default("login_service")
     def _login_service_default(self):
@@ -243,7 +244,7 @@ async def update_auth_model(self, auth_model):
 
         user_groups = set()
         if self.allowed_google_groups or self.admin_google_groups:
-            user_groups = self._fetch_member_groups(user_email, user_domain)
+            user_groups = await self._fetch_member_groups(user_email, user_domain)
         # sets are not JSONable, cast to list for auth_state
         user_info["google_groups"] = list(user_groups)
 
@@ -314,6 +315,36 @@ async def check_allowed(self, username, auth_model):
         # users should be explicitly allowed via config, otherwise they aren't
         return False
 
+    def _get_service_credentials(self, user_email_domain):
+        """
+        Returns the stored credentials or fetches and stores new ones.
+
+        Checks if the credentials are valid before returning them. Refreshes
+        if necessary and stores the refreshed credentials.
+        """
+        if (
+            user_email_domain not in self._service_credentials
+            or not self._is_token_valid(user_email_domain)
+        ):
+            self._service_credentials[user_email_domain] = (
+                self._setup_service_credentials(user_email_domain)
+            )
+
+        return self._service_credentials
+
+    def _is_token_valid(self, user_email_domain):
+        """
+        Checks if the stored token is valid.
+        """
+        if not self._service_credentials[user_email_domain]:
+            return False
+        if not self._service_credentials[user_email_domain].token:
+            return False
+        if self._service_credentials[user_email_domain].expired:
+            return False
+
+        return True
+
     def _service_client_credentials(self, scopes, user_email_domain):
         """
         Return a configured service client credentials for the API.
@@ -338,71 +369,57 @@ def _service_client_credentials(self, scopes, user_email_domain):
 
         return credentials
 
-    def _service_client(self, service_name, service_version, credentials, http=None):
+    def _setup_service_credentials(self, user_email_domain):
         """
-        Return a configured service client for the API.
+        Set up the oauth credentials for Google API.
         """
+        credentials = self._service_client_credentials(
+            scopes=[f"{self.google_api_url}/auth/admin.directory.group.readonly"],
+            user_email_domain=user_email_domain,
+        )
+
         try:
-            from googleapiclient.discovery import build
+            from google.auth.transport import requests
         except:
             raise ImportError(
-                "Could not import googleapiclient.discovery's build,"
+                "Could not import google.auth.transport's requests,"
                 "you may need to run 'pip install oauthenticator[googlegroups]' or not declare google groups"
             )
 
-        self.log.debug(
-            f"service_name is {service_name}, service_version is {service_version}"
-        )
-
-        return build(
-            serviceName=service_name,
-            version=service_version,
-            credentials=credentials,
-            cache_discovery=False,
-            http=http,
-        )
-
-    def _setup_service(self, user_email_domain, http=None):
-        """
-        Set up the service client for Google API.
-        """
-        credentials = self._service_client_credentials(
-            scopes=[f"{self.google_api_url}/auth/admin.directory.group.readonly"],
-            user_email_domain=user_email_domain,
-        )
-        service = self._service_client(
-            service_name='admin',
-            service_version='directory_v1',
-            credentials=credentials,
-            http=http,
-        )
-        return service
+        request = requests.Request()
+        credentials.refresh(request)
+        self.log.debug(f"Credentials refreshed for {user_email_domain}")
+        return credentials
 
-    def _fetch_member_groups(
+    async def _fetch_member_groups(
         self,
         member_email,
         user_email_domain,
         http=None,
         checked_groups=None,
         processed_groups=None,
+        credentials=None,
     ):
         """
         Return a set with the google groups a given user/group is a member of, including nested groups if allowed.
         """
-        # FIXME: When this function is used and waiting for web request
-        #        responses, JupyterHub gets blocked from doing other things.
-        #        Ideally the web requests should be made using an async client
-        #        that can be awaited while JupyterHub handles other things.
-        #
-        if not hasattr(self, 'service'):
-            self.service = self._setup_service(user_email_domain, http)
-
+        # WARNING: There's a race condition here if multiple users login at the same time.
+        # This is currently ignored.
+        credentials = credentials or self._get_service_credentials(user_email_domain)
+        token = credentials[user_email_domain].token
         checked_groups = checked_groups or set()
         processed_groups = processed_groups or set()
 
-        resp = self.service.groups().list(userKey=member_email).execute()
+        headers = {'Authorization': f'Bearer {token}'}
+        url = f'https://www.googleapis.com/admin/directory/v1/groups?userKey={member_email}'
+        group_data = await self.httpfetch(
+            url, headers=headers, label="fetching google groups"
+        )
+
         member_groups = {
-            g['email'].split('@')[0] for g in resp.get('groups', []) if g.get('email')
+            g['email'].split('@')[0]
+            for g in group_data.get('groups', [])
+            if g.get('email')
         }
         self.log.debug(f"Fetched groups for {member_email}: {member_groups}")
 
@@ -414,7 +431,7 @@ def _fetch_member_groups(
                 if group in processed_groups:
                     continue
                 processed_groups.add(group)
-                nested_groups = self._fetch_member_groups(
+                nested_groups = await self._fetch_member_groups(
                     f"{group}@{user_email_domain}",
                     user_email_domain,
                     http,
diff --git a/setup.py b/setup.py
index 480e04d3..615695be 100644
--- a/setup.py
+++ b/setup.py
@@ -91,7 +91,6 @@ def run(self):
     # googlegroups is required for use of GoogleOAuthenticator configured with
     # either admin_google_groups and/or allowed_google_groups.
     'googlegroups': [
-        'google-api-python-client',
         'google-auth-oauthlib',
     ],
     # mediawiki is required for use of MWOAuthenticator
@@ -105,7 +104,6 @@ def run(self):
         'pytest-cov',
         'requests-mock',
         # dependencies from googlegroups:
-        'google-api-python-client',
         'google-auth-oauthlib',
         # dependencies from mediawiki:
         'mwoauth>=0.3.8',


Test patch:
diff --git a/oauthenticator/tests/test_google.py b/oauthenticator/tests/test_google.py
index 4c3a9e0c..070de014 100644
--- a/oauthenticator/tests/test_google.py
+++ b/oauthenticator/tests/test_google.py
@@ -3,6 +3,7 @@
 import logging
 import re
 from unittest import mock
+from unittest.mock import AsyncMock
 
 from pytest import fixture, mark, raises
 from traitlets.config import Config
@@ -211,7 +212,7 @@ async def test_google(
     handled_user_model = user_model("user1@example.com", "user1")
     handler = google_client.handler_for_user(handled_user_model)
     with mock.patch.object(
-        authenticator, "_fetch_member_groups", lambda *args: {"group1"}
+        authenticator, "_fetch_member_groups", AsyncMock(return_value={"group1"})
     ):
         auth_model = await authenticator.get_authenticated_user(handler, None)