feat(flags): add Unleash feature flagging integration (#3888)

Adds an integration for tracking flag evaluations from [Unleash](https://www.getunleash.io/) customers. 

Implementation
Unleash has no native support for evaluation hooks/listeners, unless the user opts in for each flag. Therefore we decided to patch the `is_enabled` and `get_variant` methods on the `UnleashClient` class. The methods are wrapped and the only side effect is writing to Sentry scope, so users shouldn't see any change in behavior. 

We patch one `UnleashClient` instance instead of the whole class. The reasons for this are described in
- #3895

It's also safer to not modify the unleash import.

References
- https://develop.sentry.dev/sdk/expected-features/#feature-flags
- https://docs.getunleash.io/reference/sdks/python for methods we're patching/wrapping

---------

Co-authored-by: Anton Pirker <[email protected]>
Co-authored-by: Colton Allen <[email protected]>

Author: 3 people

Diff for: .github/workflows/test-integrations-misc.yml

@@ -79,6 +79,10 @@ jobs:
         run: |
           set -x # print commands that are executed
           ./scripts/runtox.sh "py${{ matrix.python-version }}-typer-latest"
+      - name: Test unleash latest
+        run: |
+          set -x # print commands that are executed
+          ./scripts/runtox.sh "py${{ matrix.python-version }}-unleash-latest"
       - name: Generate coverage XML (Python 3.6)
         if: ${{ !cancelled() && matrix.python-version == '3.6' }}
         run: |
@@ -163,6 +167,10 @@ jobs:
         run: |
           set -x # print commands that are executed
           ./scripts/runtox.sh --exclude-latest "py${{ matrix.python-version }}-typer"
+      - name: Test unleash pinned
+        run: |
+          set -x # print commands that are executed
+          ./scripts/runtox.sh --exclude-latest "py${{ matrix.python-version }}-unleash"
       - name: Generate coverage XML (Python 3.6)
         if: ${{ !cancelled() && matrix.python-version == '3.6' }}
         run: |

Diff for: requirements-linting.txt

@@ -17,4 +17,5 @@ pre-commit # local linting
 httpcore
 openfeature-sdk
 launchdarkly-server-sdk
+UnleashClient
 typer

Diff for: scripts/split_tox_gh_actions/split_tox_gh_actions.py

@@ -133,6 +133,7 @@
         "pure_eval",
         "trytond",
         "typer",
+        "unleash",
     ],
 }
 

Diff for: sentry_sdk/integrations/unleash.py

@@ -0,0 +1,55 @@
+from functools import wraps
+from typing import Any
+
+import sentry_sdk
+from sentry_sdk.flag_utils import flag_error_processor
+from sentry_sdk.integrations import Integration, DidNotEnable
+
+try:
+    from UnleashClient import UnleashClient
+except ImportError:
+    raise DidNotEnable("UnleashClient is not installed")
+
+
+class UnleashIntegration(Integration):
+    identifier = "unleash"
+
+    @staticmethod
+    def setup_once():
+        # type: () -> None
+        # Wrap and patch evaluation methods (instance methods)
+        old_is_enabled = UnleashClient.is_enabled
+        old_get_variant = UnleashClient.get_variant
+
+        @wraps(old_is_enabled)
+        def sentry_is_enabled(self, feature, *args, **kwargs):
+            # type: (UnleashClient, str, *Any, **Any) -> Any
+            enabled = old_is_enabled(self, feature, *args, **kwargs)
+
+            # We have no way of knowing what type of unleash feature this is, so we have to treat
+            # it as a boolean / toggle feature.
+            flags = sentry_sdk.get_current_scope().flags
+            flags.set(feature, enabled)
+
+            return enabled
+
+        @wraps(old_get_variant)
+        def sentry_get_variant(self, feature, *args, **kwargs):
+            # type: (UnleashClient, str, *Any, **Any) -> Any
+            variant = old_get_variant(self, feature, *args, **kwargs)
+            enabled = variant.get("enabled", False)
+
+            # Payloads are not always used as the feature's value for application logic. They
+            # may be used for metrics or debugging context instead. Therefore, we treat every
+            # variant as a boolean toggle, using the `enabled` field.
+            flags = sentry_sdk.get_current_scope().flags
+            flags.set(feature, enabled)
+
+            return variant
+
+        UnleashClient.is_enabled = sentry_is_enabled  # type: ignore
+        UnleashClient.get_variant = sentry_get_variant  # type: ignore
+
+        # Error processor
+        scope = sentry_sdk.get_current_scope()
+        scope.add_error_processor(flag_error_processor)

Diff for: setup.py

@@ -80,6 +80,7 @@ def get_file_text(file_name):
         "starlette": ["starlette>=0.19.1"],
         "starlite": ["starlite>=1.48"],
         "tornado": ["tornado>=6"],
+        "unleash": ["UnleashClient>=6.0.1"],
     },
     entry_points={
         "opentelemetry_propagator": [

Diff for: tests/conftest.py

@@ -10,6 +10,7 @@
 import pytest
 import jsonschema
 
+
 try:
     import gevent
 except ImportError:

Diff for: tests/integrations/unleash/__init__.py

@@ -0,0 +1,3 @@
+import pytest
+
+pytest.importorskip("UnleashClient")