ServiceApiClient: refactor construction, use thread-local instances

app/__init__.py

@@ -1,4 +1,6 @@
 import os
+from collections.abc import Callable
+from contextvars import ContextVar
 
 import jinja2
 from flask import current_app, make_response, render_template
@@ -7,6 +9,8 @@
 from notifications_utils import logging, request_helper
 from notifications_utils.base64_uuid import base64_to_uuid, uuid_to_base64
 from notifications_utils.clients.statsd.statsd_client import StatsdClient
+from notifications_utils.local_vars import LazyLocalGetter
+from werkzeug.local import LocalProxy
 from werkzeug.routing import BaseConverter, ValidationError
 
 from app.asset_fingerprinter import AssetFingerprinter
@@ -16,7 +20,20 @@
 metrics = GDSMetrics()
 statsd_client = StatsdClient()
 asset_fingerprinter = AssetFingerprinter()
-service_api_client = ServiceApiClient()
+
+memo_resetters: list[Callable] = []
+
+#
+# "clients" that need thread-local copies
+#
+
+_service_api_client_context_var: ContextVar[ServiceApiClient] = ContextVar("service_api_client")
+get_service_api_client: LazyLocalGetter[ServiceApiClient] = LazyLocalGetter(
+    _service_api_client_context_var,
+    lambda: ServiceApiClient(app=current_app),
+)
+memo_resetters.append(lambda: get_service_api_client.clear())
+service_api_client = LocalProxy(get_service_api_client)
 
 
 class Base64UUIDConverter(BaseConverter):
@@ -61,8 +78,6 @@ def create_app(application):
 
     register_errorhandlers(application)
 
-    service_api_client.init_app(application)
-
 
 def init_app(application):
     application.after_request(useful_headers_after_request)
@@ -76,6 +91,14 @@ def inject_global_template_variables():
         }
 
 
+def reset_memos():
+    """
+    Reset all memos registered in memo_resetters
+    """
+    for resetter in memo_resetters:
+        resetter()
+
+
 #  https://www.owasp.org/index.php/List_of_useful_HTTP_headers
 def useful_headers_after_request(response):
     response.headers.add("X-Robots-Tag", "noindex, nofollow")

app/notify_client/service_api_client.py

@@ -17,16 +17,15 @@ def generate_headers(self, api_token):
 
 
 class ServiceApiClient:
-    def __init__(self):
-        self.api_client = None
-
-    def init_app(self, application):
+    def __init__(self, app):
         self.api_client = OnwardsRequestNotificationsAPIClient(
-            base_url=application.config["API_HOST_NAME"],
-            api_key="a" * 75,
+            "x" * 100,
+            base_url=app.config["API_HOST_NAME"],
         )
-        self.api_client.service_id = application.config["ADMIN_CLIENT_USER_NAME"]
-        self.api_client.api_key = application.config["ADMIN_CLIENT_SECRET"]
+        # our credential lengths aren't what NotificationsAPIClient's __init__ will expect
+        # given it's designed for destructuring end-user api keys
+        self.api_client.service_id = app.config["ADMIN_CLIENT_USER_NAME"]
+        self.api_client.api_key = app.config["ADMIN_CLIENT_SECRET"]
 
     def get_service(self, service_id):
         """

requirements.in

@@ -5,10 +5,10 @@ Flask-WTF==1.2.1
 
 whitenoise==6.2.0  #manages static assets
 
-notifications-python-client==8.0.1
+notifications-python-client==10.0.0
 
 # Run `make bump-utils` to update to the latest version
-notifications-utils @ git+https://github.com/alphagov/notifications-utils.git@82.1.1
+notifications-utils @ git+https://github.com/alphagov/notifications-utils.git@82.6.1
 
 # gds-metrics requires prometheseus 0.2.0, override that requirement as later versions bring significant performance gains
 prometheus-client==0.15.0

requirements.txt

@@ -78,9 +78,9 @@ markupsafe==2.1.1
     #   wtforms
 mistune==0.8.4
     # via notifications-utils
-notifications-python-client==8.0.1
+notifications-python-client==10.0.0
     # via -r requirements.in
-notifications-utils @ git+https://github.com/alphagov/notifications-utils.git@82.1.1
+notifications-utils @ git+https://github.com/alphagov/notifications-utils.git@82.6.1
     # via -r requirements.in
 ordered-set==4.1.0
     # via notifications-utils

tests/app/notify_client/test_service_api_client.py

@@ -6,16 +6,15 @@
 
 
 def test_client_gets_service(mocker):
-    client = ServiceApiClient()
+    client = ServiceApiClient(mocker.MagicMock())
     mock_api_client = mocker.patch.object(client, "api_client")
 
     client.get_service("foo")
     mock_api_client.get.assert_called_once_with("/service/foo")
 
 
 def test_client_onward_headers(app_, rmock, service_id, sample_service):
-    client = ServiceApiClient()
-    client.init_app(app_)
+    client = ServiceApiClient(app_)
 
     rmock.get(
         "{}/service/{}".format(
@@ -41,8 +40,7 @@ def test_client_onward_headers(app_, rmock, service_id, sample_service):
 
 
 def test_client_no_onward_headers(app_, rmock, service_id, sample_service):
-    client = ServiceApiClient()
-    client.init_app(app_)
+    client = ServiceApiClient(app_)
 
     rmock.get(
         "{}/service/{}".format(

tests/conftest.py

@@ -5,20 +5,22 @@
 import requests_mock
 from flask import Flask, current_app
 
-from app import create_app
+from app import create_app, reset_memos
 
 
 @pytest.fixture
 def app_(request):
     app = Flask("app")
     create_app(app)
 
+    reset_memos()
     ctx = app.app_context()
     ctx.push()
 
     yield app
 
     ctx.pop()
+    reset_memos()
 
 
 @pytest.fixture(scope="function")