fix: retry flags only on transport errors

Author: marandaneto

posthog/__init__.py

@@ -67,6 +67,7 @@
     FlagDefinitionCacheProvider as FlagDefinitionCacheProvider,
 )
 from posthog.request import (
+    DEFAULT_FEATURE_FLAGS_REQUEST_MAX_RETRIES as DEFAULT_FEATURE_FLAGS_REQUEST_MAX_RETRIES,
     disable_connection_reuse as disable_connection_reuse,
     enable_keep_alive as enable_keep_alive,
     set_socket_options as set_socket_options,
@@ -322,6 +323,9 @@ def get_tags() -> Dict[str, Any]:
         attributed to the person normally.
     feature_flags_request_timeout_seconds: Timeout in seconds for feature flag
         and remote config requests.
+    feature_flags_request_max_retries: Number of retries for feature flag
+        requests after network, transport, or timeout failures. Defaults to 1.
+        Set to 0 to disable retries.
     super_properties: Properties merged into every captured event.
     enable_exception_autocapture: Automatically capture uncaught exceptions.
     log_captured_exceptions: Also log exceptions captured by error tracking.
@@ -365,6 +369,7 @@ def get_tags() -> Dict[str, Any]:
 disable_geoip = True  # type: bool
 is_server = True  # type: bool
 feature_flags_request_timeout_seconds = 3  # type: int
+feature_flags_request_max_retries = DEFAULT_FEATURE_FLAGS_REQUEST_MAX_RETRIES  # type: int
 super_properties = None  # type: Optional[Dict]
 enable_exception_autocapture = False  # type: bool
 log_captured_exceptions = False  # type: bool
@@ -1156,6 +1161,7 @@ def setup() -> Client:
             disable_geoip=disable_geoip,
             is_server=is_server,
             feature_flags_request_timeout_seconds=feature_flags_request_timeout_seconds,
+            feature_flags_request_max_retries=feature_flags_request_max_retries,
             super_properties=super_properties,
             # TODO: Currently this monitoring begins only when the Client is initialised (which happens when you do something with the SDK)
             # This kind of initialisation is very annoying for exception capture. We need to figure out a way around this,

posthog/client.py

@@ -69,6 +69,7 @@
     AI_EVENTS_ENDPOINT,
     EVENTS_ENDPOINT,
     APIError,
+    DEFAULT_FEATURE_FLAGS_REQUEST_MAX_RETRIES,
     QuotaLimitError,
     RequestsConnectionError,
     RequestsTimeout,
@@ -240,6 +241,7 @@ def __init__(
         is_server=True,
         historical_migration=False,
         feature_flags_request_timeout_seconds=3,
+        feature_flags_request_max_retries=DEFAULT_FEATURE_FLAGS_REQUEST_MAX_RETRIES,
         super_properties=None,
         enable_exception_autocapture=False,
         log_captured_exceptions=False,
@@ -296,6 +298,9 @@ def __init__(
             historical_migration: Mark events as historical migration imports.
             feature_flags_request_timeout_seconds: Timeout in seconds for feature
                 flag and remote config requests.
+            feature_flags_request_max_retries: Number of retries for feature flag
+                requests after network, transport, or timeout failures. Defaults
+                to 1. Set to 0 to disable retries.
             super_properties: Properties merged into every captured event.
             enable_exception_autocapture: Automatically capture uncaught
                 exceptions.
@@ -376,6 +381,9 @@ def __init__(
         self.feature_flags_request_timeout_seconds = (
             feature_flags_request_timeout_seconds
         )
+        self.feature_flags_request_max_retries = max(
+            0, feature_flags_request_max_retries
+        )
         self.poller: Optional[Poller] = None
         self.distinct_ids_feature_flags_reported = SizeLimitedDict(MAX_DICT_SIZE, set)
         self.flag_fallback_cache_url = flag_fallback_cache_url
@@ -895,10 +903,18 @@ def _get_flags_decision(
         if flag_keys_to_evaluate:
             request_data["flag_keys_to_evaluate"] = flag_keys_to_evaluate
 
+        flag_request_options: Dict[str, Any] = {}
+        if (
+            self.feature_flags_request_max_retries
+            != DEFAULT_FEATURE_FLAGS_REQUEST_MAX_RETRIES
+        ):
+            flag_request_options["max_retries"] = self.feature_flags_request_max_retries
+
         resp_data = flags(
             self.api_key,
             self.host,
             timeout=self.feature_flags_request_timeout_seconds,
+            **flag_request_options,
             **request_data,
         )
 

posthog/request.py

@@ -2,6 +2,7 @@
 import logging
 import re
 import socket
+import time
 from dataclasses import dataclass
 from datetime import date, datetime, timezone
 from gzip import GzipFile
@@ -41,8 +42,8 @@
     if hasattr(socket, attr):
         KEEP_ALIVE_SOCKET_OPTIONS.append((socket.SOL_TCP, getattr(socket, attr), value))
 
-# Status codes that indicate transient server errors worth retrying
-RETRY_STATUS_FORCELIST = [408, 500, 502, 503, 504]
+DEFAULT_FEATURE_FLAGS_REQUEST_MAX_RETRIES = 1
+FEATURE_FLAGS_RETRY_BACKOFF_SECONDS = 0.3
 
 
 def _mask_tokens_in_url(url: str) -> str:
@@ -90,23 +91,14 @@ def _build_session(socket_options: Optional[SocketOptions] = None) -> requests.S
 def _build_flags_session(
     socket_options: Optional[SocketOptions] = None,
 ) -> requests.Session:
-    """
-    Build a session for feature flag requests with POST retries.
+    """Build a session for feature flag requests.
 
-    Feature flag requests are idempotent (read-only), so retrying POST
-    requests is safe. This session retries on transient server errors
-    (408, 5xx) and network failures with exponential backoff
-    (0.5s, 1s delays between retries).
+    /flags retries are handled explicitly in ``flags()`` so that only
+    transport failures are retried. HTTP status responses must surface as API
+    errors without retrying.
     """
     adapter = HTTPAdapterWithSocketOptions(
-        max_retries=Retry(
-            total=2,
-            connect=2,
-            read=2,
-            backoff_factor=0.5,
-            status_forcelist=RETRY_STATUS_FORCELIST,
-            allowed_methods=["POST"],
-        ),
+        max_retries=Retry(total=0, connect=0, read=0, status=0),
         socket_options=socket_options,
     )
     session = requests.Session()
@@ -306,26 +298,41 @@ def _process_response(
         raise APIError(res.status_code, res.text, retry_after=retry_after)
 
 
+def _feature_flags_retry_delay(failed_attempt: int) -> float:
+    return FEATURE_FLAGS_RETRY_BACKOFF_SECONDS * (2**failed_attempt)
+
+
 def flags(
     api_key: str,
     host: Optional[str] = None,
     gzip: bool = False,
     timeout: int = 15,
+    max_retries: int = DEFAULT_FEATURE_FLAGS_REQUEST_MAX_RETRIES,
     **kwargs,
 ) -> Any:
-    """Post the kwargs to the flags API endpoint with automatic retries."""
-    res = post(
-        api_key,
-        host,
-        "/flags/?v=2",
-        gzip,
-        timeout,
-        session=_get_flags_session(),
-        **kwargs,
-    )
-    return _process_response(
-        res, success_message="Feature flags evaluated successfully"
-    )
+    """Post the kwargs to the flags API endpoint with transport retries."""
+    retries = max(0, max_retries)
+    failed_attempt = 0
+
+    while True:
+        try:
+            res = post(
+                api_key,
+                host,
+                "/flags/?v=2",
+                gzip,
+                timeout,
+                session=_get_flags_session(),
+                **kwargs,
+            )
+            return _process_response(
+                res, success_message="Feature flags evaluated successfully"
+            )
+        except (requests.exceptions.ConnectionError, requests.exceptions.Timeout):
+            if failed_attempt >= retries:
+                raise
+            time.sleep(_feature_flags_retry_delay(failed_attempt))
+            failed_attempt += 1
 
 
 def remote_config(

posthog/test/test_client.py

@@ -984,6 +984,21 @@ def test_basic_capture_with_feature_flags_returns_active_only(self, patch_flags)
                 device_id=None,
             )
 
+    @mock.patch("posthog.client.flags")
+    def test_feature_flags_request_max_retries_is_forwarded_when_configured(
+        self, patch_flags
+    ):
+        patch_flags.return_value = {"featureFlags": {}, "featureFlagPayloads": {}}
+        client = Client(
+            FAKE_TEST_API_KEY,
+            feature_flags_request_max_retries=0,
+            personal_api_key=FAKE_TEST_API_KEY,
+        )
+
+        client.get_all_flags("distinct_id")
+
+        self.assertEqual(patch_flags.call_args.kwargs["max_retries"], 0)
+
     @mock.patch("posthog.client.flags")
     def test_basic_capture_with_feature_flags_and_disable_geoip_returns_correctly(
         self, patch_flags