chore: update endpoint for flags local eval (#509)

* chore: update endpoint for flags local eval

* remove imports

Author: patricio-posthog

.sampo/changesets/flags-definitions-endpoint.md

@@ -0,0 +1,5 @@
+---
+pypi/posthog: patch
+---
+
+feat(flags): switch local evaluation polling from `/api/feature_flag/local_evaluation` to `/flags/definitions`

posthog/client.py

@@ -1287,55 +1287,19 @@ def _load_feature_flags(self):
         if should_fetch:
             self._fetch_feature_flags_from_api()
 
-    # Default (Django) endpoint for local evaluation
-    _DEFAULT_LOCAL_EVAL_ENDPOINT = "/api/feature_flag/local_evaluation/"
-
-    def _get_local_eval_endpoint(self):
-        """Get the local evaluation endpoint URL, configurable via env var."""
-        return os.environ.get(
-            "POSTHOG_LOCAL_EVALUATION_ENDPOINT",
-            self._DEFAULT_LOCAL_EVAL_ENDPOINT,
-        )
-
     def _fetch_feature_flags_from_api(self):
         """Fetch feature flags from the PostHog API."""
         try:
             # Store old flags to detect changes
             old_flags_by_key: dict[str, dict] = self.feature_flags_by_key or {}
 
-            endpoint = self._get_local_eval_endpoint()
-            url = f"{endpoint}?token={self.api_key}&send_cohorts"
-            # Ensure URL has leading slash
-            if not url.startswith("/"):
-                url = f"/{url}"
-
-            try:
-                response = get(
-                    self.personal_api_key,
-                    url,
-                    self.host,
-                    timeout=10,
-                    etag=self._flags_etag,
-                )
-            except Exception as e:
-                # Fall back to the stable Django endpoint when the custom endpoint
-                # (e.g. the Rust-backed /flags/definitions) fails. This enables a
-                # zero-downtime gradual migration: the custom endpoint is tried first
-                # and, on any error, flag evaluation degrades transparently to the
-                # default rather than being blocked entirely.
-                if endpoint != self._DEFAULT_LOCAL_EVAL_ENDPOINT:
-                    self.log.warning(
-                        f"[FEATURE FLAGS] Custom endpoint {endpoint} failed ({e}), falling back to {self._DEFAULT_LOCAL_EVAL_ENDPOINT}"
-                    )
-                    response = get(
-                        self.personal_api_key,
-                        f"{self._DEFAULT_LOCAL_EVAL_ENDPOINT}?token={self.api_key}&send_cohorts",
-                        self.host,
-                        timeout=10,
-                        etag=self._flags_etag,
-                    )
-                else:
-                    raise
+            response = get(
+                self.personal_api_key,
+                f"/flags/definitions?token={self.api_key}&send_cohorts",
+                self.host,
+                timeout=10,
+                etag=self._flags_etag,
+            )
 
             # Update stored ETag (clear if server stops sending one)
             self._flags_etag = response.etag

posthog/test/test_feature_flags.py

@@ -1,11 +1,9 @@
 import datetime
-import os
 import unittest
 
 import mock
 from dateutil import parser, tz
 from freezegun import freeze_time
-from parameterized import parameterized
 
 from posthog.client import Client
 from posthog.feature_flags import (
@@ -3782,80 +3780,6 @@ def test_get_all_flags_fallback_when_device_id_missing_for_some_flags(
         self.assertEqual(patch_flags.call_count, 1)
 
 
-class TestLocalEvalEndpointConfig(unittest.TestCase):
-    @classmethod
-    def setUpClass(cls):
-        cls.capture_patch = mock.patch.object(Client, "capture")
-        cls.capture_patch.start()
-
-    @classmethod
-    def tearDownClass(cls):
-        cls.capture_patch.stop()
-
-    @parameterized.expand(
-        [
-            ("custom_endpoint", "/flags/definitions", "/flags/definitions?"),
-            ("default_endpoint", None, "/api/feature_flag/local_evaluation/"),
-        ]
-    )
-    @mock.patch("posthog.client.get")
-    def test_endpoint_selection(self, _name, env_value, expected_prefix, patch_get):
-        patch_get.return_value = GetResponse(
-            data={"flags": [], "group_type_mapping": {}},
-            etag=None,
-            not_modified=False,
-        )
-        env = {"POSTHOG_LOCAL_EVALUATION_ENDPOINT": env_value} if env_value else {}
-        with mock.patch.dict("os.environ", env, clear=False):
-            if env_value is None:
-                os.environ.pop("POSTHOG_LOCAL_EVALUATION_ENDPOINT", None)
-            client = Client(FAKE_TEST_API_KEY, personal_api_key="test-key")
-            client._fetch_feature_flags_from_api()
-            call_url = patch_get.call_args[0][1]
-            self.assertTrue(
-                call_url.startswith(expected_prefix),
-                f"Expected URL starting with {expected_prefix}, got: {call_url}",
-            )
-
-    @parameterized.expand(
-        [
-            ("custom_endpoint_falls_back", "/flags/definitions", 2),
-            ("default_endpoint_no_fallback", None, 1),
-        ]
-    )
-    @mock.patch("posthog.client.get")
-    def test_endpoint_fallback_on_failure(
-        self, _name, env_value, expected_call_count, patch_get
-    ):
-        success_response = GetResponse(
-            data={"flags": [], "group_type_mapping": {}},
-            etag=None,
-            not_modified=False,
-        )
-        if expected_call_count == 2:
-            patch_get.side_effect = [Exception("connection refused"), success_response]
-        else:
-            patch_get.side_effect = Exception("connection refused")
-
-        env = {"POSTHOG_LOCAL_EVALUATION_ENDPOINT": env_value} if env_value else {}
-        with mock.patch.dict("os.environ", env, clear=False):
-            if env_value is None:
-                os.environ.pop("POSTHOG_LOCAL_EVALUATION_ENDPOINT", None)
-            client = Client(FAKE_TEST_API_KEY, personal_api_key="test-key")
-            client._fetch_feature_flags_from_api()
-            self.assertEqual(patch_get.call_count, expected_call_count)
-            if expected_call_count == 2:
-                # First call used custom endpoint, second fell back to default
-                self.assertTrue(
-                    patch_get.call_args_list[0][0][1].startswith("/flags/definitions?")
-                )
-                self.assertTrue(
-                    patch_get.call_args_list[1][0][1].startswith(
-                        "/api/feature_flag/local_evaluation/"
-                    )
-                )
-
-
 class TestMatchProperties(unittest.TestCase):
     def property(self, key, value, operator=None):
         result = {"key": key, "value": value}