Merge pull request #3075 from alphagov/cache-provider-lookup

Cache provider lookups for 10 seconds

app/delivery/send_to_providers.py

@@ -1,7 +1,7 @@
 import random
 from urllib import parse
 from datetime import datetime, timedelta
-
+from cachetools import TTLCache, cached
 from flask import current_app
 from notifications_utils.recipients import (
     validate_and_format_phone_number,
@@ -148,6 +148,10 @@ def update_notification_to_sending(notification, provider):
     dao_update_notification(notification)
 
 
+provider_cache = TTLCache(maxsize=8, ttl=10)
+
+
+@cached(cache=provider_cache)
 def provider_to_use(notification_type, international=False):
     active_providers = [
         p for p in get_provider_details_by_notification_type(notification_type, international) if p.active

tests/app/delivery/test_send_to_providers.py

@@ -34,6 +34,12 @@ from tests.app.db import (
 )
 
 
+def setup_function(_function):
+    # pytest will run this function before each test. It makes sure the
+    # state of the cache is not shared between tests.
+    send_to_providers.provider_cache.clear()
+
+
 def test_provider_to_use_should_return_random_provider(mocker, notify_db_session):
     mmg = get_provider_details_by_identifier('mmg')
     firetext = get_provider_details_by_identifier('firetext')
@@ -47,6 +53,21 @@ def test_provider_to_use_should_return_random_provider(mocker, notify_db_session
     assert ret.get_name() == 'mmg'
 
 
+def test_provider_to_use_should_cache_repeated_calls(mocker, notify_db_session):
+    mock_choices = mocker.patch(
+        'app.delivery.send_to_providers.random.choices',
+        wraps=send_to_providers.random.choices,
+    )
+
+    results = [
+        send_to_providers.provider_to_use('sms', international=False)
+        for _ in range(10)
+    ]
+
+    assert all(result == results[0] for result in results)
+    assert len(mock_choices.call_args_list) == 1
+
+
 def test_provider_to_use_should_only_return_mmg_for_international(mocker, notify_db_session):
     mmg = get_provider_details_by_identifier('mmg')
     mock_choices = mocker.patch('app.delivery.send_to_providers.random.choices', return_value=[mmg])