Better handle initialization if cache not present and Unleash server not accessible (#30)

* Add logging documentation.

* Better handles cases where cache is not present and Unleash server is not accessible during startup.

* Update changelog.

* Fix flake8 issues.

* Make integration scrip generic again.

* Make integration scrip generic again.

Author: ivanklee86

UnleashClient/loader.py

@@ -45,32 +45,36 @@ def load_features(cache: FileCache,
     :return:
     """
     # Pull raw provisioning from cache.
-    feature_provisioning = cache[FEATURES_URL]
-
-    # Parse provisioning
-    parsed_features = {}
-    feature_names = [d["name"] for d in feature_provisioning["features"]]
-
-    for provisioning in feature_provisioning["features"]:
-        parsed_features[provisioning["name"]] = provisioning
-
-    # Delete old features/cache
-    for feature in list(feature_toggles.keys()):
-        if feature not in feature_names:
-            del feature_toggles[feature]
-
-    # Update existing objects
-    for feature in feature_toggles.keys():
-        feature_for_update = feature_toggles[feature]
-        strategies = parsed_features[feature]["strategies"]
-
-        feature_for_update.enabled = parsed_features[feature]["enabled"]
-        if strategies:
-            parsed_strategies = _create_strategies(parsed_features[feature], strategy_mapping)
-            feature_for_update.strategies = parsed_strategies
-
-    # Handle creation or deletions
-    new_features = list(set(feature_names) - set(feature_toggles.keys()))
-
-    for feature in new_features:
-        feature_toggles[feature] = _create_feature(parsed_features[feature], strategy_mapping)
+    try:
+        feature_provisioning = cache[FEATURES_URL]
+
+        # Parse provisioning
+        parsed_features = {}
+        feature_names = [d["name"] for d in feature_provisioning["features"]]
+
+        for provisioning in feature_provisioning["features"]:
+            parsed_features[provisioning["name"]] = provisioning
+
+        # Delete old features/cache
+        for feature in list(feature_toggles.keys()):
+            if feature not in feature_names:
+                del feature_toggles[feature]
+
+        # Update existing objects
+        for feature in feature_toggles.keys():
+            feature_for_update = feature_toggles[feature]
+            strategies = parsed_features[feature]["strategies"]
+
+            feature_for_update.enabled = parsed_features[feature]["enabled"]
+            if strategies:
+                parsed_strategies = _create_strategies(parsed_features[feature], strategy_mapping)
+                feature_for_update.strategies = parsed_strategies
+
+        # Handle creation or deletions
+        new_features = list(set(feature_names) - set(feature_toggles.keys()))
+
+        for feature in new_features:
+            feature_toggles[feature] = _create_feature(parsed_features[feature], strategy_mapping)
+    except KeyError as cache_exception:
+        LOGGER.warning("Cache Exception: %s", cache_exception)
+        LOGGER.warning("Unleash client does not have cached features.  Please make sure client can communicate with Unleash server!")

UnleashClient/periodic_tasks/fetch_and_load.py

@@ -18,6 +18,6 @@ def fetch_and_load_features(url: str,
         cache[FEATURES_URL] = feature_provisioning
         cache.sync()
     else:
-        LOGGER.info("Unable to get feature flag toggles, using cached values.")
+        LOGGER.warning("Unable to get feature flag toggles, using cached provisioning.")
 
     load_features(cache, features, strategy_mapping)

docs/changelog.md

@@ -1,3 +1,8 @@
+## Next
+
+**General**
+* (Minor) Unleash client will not error if cache is not present and Unleash server not accessible during initialization.
+
 ## v2.4.0
 
 **General**

docs/index.md

@@ -40,3 +40,25 @@ Supplying application context:
 app_context = {"userId": "test@email.com"}
 client.is_enabled("User ID Toggle", app_context)
 ```
+
+## Logging
+
+Unleash Client uses the built-in logging facility to show information about errors, background jobs (feature-flag updates and metrics), et cetera.
+
+It's highly recommended that users implement
+
+To see what's going on when PoCing code, you can use the following:
+```python
+import logging
+import sys
+
+root = logging.getLogger()
+root.setLevel(logging.INFO)
+
+handler = logging.StreamHandler(sys.stdout)
+handler.setLevel(logging.DEBUG)
+formatter = logging.Formatter('%(asctime)s - %(name)s - %(levelname)s - %(message)s')
+handler.setFormatter(formatter)
+root.addHandler(handler)
+
+``` 

tests/integration_tests/integration.py

@@ -15,7 +15,6 @@
 root.addHandler(handler)
 # ---
 
-
 my_client = UnleashClient(
     url="http://localhost:4242/api",
     app_name="pyIvan"

tests/unit_tests/test_client.py

@@ -30,20 +30,41 @@ def __call__(self, context: dict = None) -> bool:
 
 
 @pytest.fixture()
-def unleash_client():
-    unleash_client = UnleashClient(URL, APP_NAME, refresh_interval=REFRESH_INTERVAL, metrics_interval=METRICS_INTERVAL)
+def unleash_client(tmpdir):
+    unleash_client = UnleashClient(
+        URL,
+        APP_NAME,
+        refresh_interval=REFRESH_INTERVAL,
+        metrics_interval=METRICS_INTERVAL,
+        cache_directory=tmpdir.dirname
+    )
     yield unleash_client
     unleash_client.destroy()
 
 
 @pytest.fixture()
-def unleash_client_toggle_only():
-    unleash_client = UnleashClient(URL,
-                                   APP_NAME,
-                                   refresh_interval=REFRESH_INTERVAL,
-                                   metrics_interval=METRICS_INTERVAL,
-                                   disable_registration=True,
-                                   disable_metrics=True)
+def unleash_client_nodestroy(tmpdir):
+    unleash_client = UnleashClient(
+        URL,
+        APP_NAME,
+        refresh_interval=REFRESH_INTERVAL,
+        metrics_interval=METRICS_INTERVAL,
+        cache_directory=tmpdir.dirname
+    )
+    yield unleash_client
+
+
+@pytest.fixture()
+def unleash_client_toggle_only(tmpdir):
+    unleash_client = UnleashClient(
+        URL,
+        APP_NAME,
+        refresh_interval=REFRESH_INTERVAL,
+        metrics_interval=METRICS_INTERVAL,
+        disable_registration=True,
+        disable_metrics=True,
+        cache_directory=str(tmpdir)
+    )
     yield unleash_client
     unleash_client.destroy()
 
@@ -112,6 +133,26 @@ def test_uc_is_enabled(unleash_client):
     assert unleash_client.is_enabled("testFlag")
 
 
+@responses.activate
+def test_uc_dirty_cache(unleash_client_nodestroy):
+    unleash_client = unleash_client_nodestroy
+    # Set up API
+    responses.add(responses.POST, URL + REGISTER_URL, json={}, status=202)
+    responses.add(responses.GET, URL + FEATURES_URL, json=MOCK_FEATURE_RESPONSE, status=200)
+    responses.add(responses.POST, URL + METRICS_URL, json={}, status=202)
+
+    # Create Unleash client and check initial load
+    unleash_client.initialize_client()
+    time.sleep(5)
+    assert unleash_client.is_enabled("testFlag")
+    unleash_client.scheduler.shutdown()
+
+    # Check that everything works if previous cache exists.
+    unleash_client.initialize_client()
+    time.sleep(5)
+    assert unleash_client.is_enabled("testFlag")
+
+
 @responses.activate
 def test_uc_is_enabled_with_context():
     # Set up API
@@ -185,3 +226,41 @@ def test_uc_disabled_registration(unleash_client_toggle_only):
 
     for api_call in responses.calls:
         assert '/api/client/features' in api_call.request.url
+
+
+@responses.activate
+def test_uc_server_error(unleash_client):
+    # Verify that Unleash Client will still fall back gracefully if SERVER ANGRY RAWR, and then recover gracefully.
+
+    unleash_client = unleash_client
+    # Set up APIs
+    responses.add(responses.POST, URL + REGISTER_URL, json={}, status=401)
+    responses.add(responses.GET, URL + FEATURES_URL, status=500)
+    responses.add(responses.POST, URL + METRICS_URL, json={}, status=401)
+
+    unleash_client.initialize_client()
+    assert not unleash_client.is_enabled("testFlag")
+
+    responses.remove(responses.GET, URL + FEATURES_URL)
+    responses.add(responses.GET, URL + FEATURES_URL, json=MOCK_FEATURE_RESPONSE, status=200)
+    time.sleep(20)
+    assert unleash_client.is_enabled("testFlag")
+
+
+@responses.activate
+def test_uc_server_error_recovery(unleash_client):
+    # Verify that Unleash Client will still fall back gracefully if SERVER ANGRY RAWR, and then recover gracefully.
+
+    unleash_client = unleash_client
+    # Set up APIs
+    responses.add(responses.POST, URL + REGISTER_URL, json={}, status=401)
+    responses.add(responses.GET, URL + FEATURES_URL, status=500)
+    responses.add(responses.POST, URL + METRICS_URL, json={}, status=401)
+
+    unleash_client.initialize_client()
+    assert not unleash_client.is_enabled("testFlag")
+
+    responses.remove(responses.GET, URL + FEATURES_URL)
+    responses.add(responses.GET, URL + FEATURES_URL, json=MOCK_FEATURE_RESPONSE, status=200)
+    time.sleep(20)
+    assert unleash_client.is_enabled("testFlag")