[FSSDK-12273] Add support for custom headers in polling datafile managers

This change adds support for custom headers in PollingConfigManager and
AuthDatafilePollingConfigManager. Users can now pass custom headers when
initializing the SDK client instance, which will be included in HTTP
requests to fetch the datafile.

Key changes:
- Added custom_headers parameter to PollingConfigManager.__init__()
- Added custom_headers parameter to AuthDatafilePollingConfigManager (inherited)
- Added custom_headers parameter to Optimizely.__init__() and passed to config managers
- Updated fetch_datafile() methods to merge custom headers with internal headers
- User-provided headers take precedence over SDK internal headers
- Added comprehensive test coverage for custom headers functionality

Reference: optimizely/javascript-sdk#1107

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: raju-opti

optimizely/config_manager.py

@@ -203,6 +203,7 @@ def __init__(
         notification_center: Optional[NotificationCenter] = None,
         skip_json_validation: Optional[bool] = False,
         retries: Optional[int] = 3,
+        custom_headers: Optional[dict[str, str]] = None,
     ):
         """ Initialize config manager. One of sdk_key or datafile has to be set to be able to use.
 
@@ -223,9 +224,12 @@ def __init__(
             skip_json_validation: Optional boolean param which allows skipping JSON schema
                                   validation upon object invocation. By default
                                   JSON schema validation will be performed.
+            custom_headers: Optional dictionary of custom headers to include in datafile fetch requests.
+                           User-provided headers take precedence over SDK internal headers.
 
         """
         self.retries = retries
+        self.custom_headers = custom_headers or {}
         self._config_ready_event = threading.Event()
         super().__init__(
             datafile=datafile,
@@ -394,6 +398,9 @@ def fetch_datafile(self) -> None:
         if self.last_modified:
             request_headers[enums.HTTPHeaders.IF_MODIFIED_SINCE] = self.last_modified
 
+        # Merge custom headers, with user-provided headers taking precedence
+        request_headers.update(self.custom_headers)
+
         try:
             session = requests.Session()
 
@@ -487,6 +494,9 @@ def fetch_datafile(self) -> None:
         if self.last_modified:
             request_headers[enums.HTTPHeaders.IF_MODIFIED_SINCE] = self.last_modified
 
+        # Merge custom headers, with user-provided headers taking precedence
+        request_headers.update(self.custom_headers)
+
         try:
             session = requests.Session()
 

optimizely/optimizely.py

@@ -76,6 +76,7 @@ def __init__(
             event_processor_options: Optional[dict[str, Any]] = None,
             settings: Optional[OptimizelySdkSettings] = None,
             cmab_service: Optional[DefaultCmabService] = None,
+            custom_headers: Optional[dict[str, str]] = None,
     ) -> None:
         """ Optimizely init method for managing Custom projects.
 
@@ -104,6 +105,8 @@ def __init__(
           default_decide_options: Optional list of decide options used with the decide APIs.
           event_processor_options: Optional dict of options to be passed to the default batch event processor.
           settings: Optional instance of OptimizelySdkSettings for sdk configuration.
+          custom_headers: Optional dictionary of custom headers to include in datafile fetch requests.
+                         User-provided headers take precedence over SDK internal headers.
         """
         self.logger_name = '.'.join([__name__, self.__class__.__name__])
         self.is_valid = True
@@ -163,6 +166,8 @@ def __init__(
         if not self.config_manager:
             if sdk_key:
                 config_manager_options['sdk_key'] = sdk_key
+                if custom_headers:
+                    config_manager_options['custom_headers'] = custom_headers
                 if datafile_access_token:
                     config_manager_options['datafile_access_token'] = datafile_access_token
                     self.config_manager = AuthDatafilePollingConfigManager(**config_manager_options)

tests/test_config_manager.py

@@ -531,6 +531,80 @@ def test_is_running(self, _):
 
         project_config_manager.stop()
 
+    def test_custom_headers(self, _):
+        """ Test that custom headers are included in datafile fetch requests. """
+        sdk_key = 'some_key'
+        custom_headers = {
+            'X-Custom-Header': 'custom_value',
+            'X-Another-Header': 'another_value'
+        }
+
+        expected_datafile_url = enums.ConfigManager.DATAFILE_URL_TEMPLATE.format(sdk_key=sdk_key)
+        test_headers = {'Last-Modified': 'New Time'}
+        test_datafile = json.dumps(self.config_dict_with_features)
+        test_response = requests.Response()
+        test_response.status_code = 200
+        test_response.headers = test_headers
+        test_response._content = test_datafile
+
+        with mock.patch('requests.Session.get', return_value=test_response) as mock_request:
+            project_config_manager = config_manager.PollingConfigManager(
+                sdk_key=sdk_key,
+                custom_headers=custom_headers
+            )
+            project_config_manager.stop()
+
+        # Assert that custom headers were included in the request
+        mock_request.assert_called_once_with(
+            expected_datafile_url,
+            headers=custom_headers,
+            timeout=enums.ConfigManager.REQUEST_TIMEOUT
+        )
+        self.assertEqual(test_headers['Last-Modified'], project_config_manager.last_modified)
+        self.assertIsInstance(project_config_manager.get_config(), project_config.ProjectConfig)
+
+    def test_custom_headers_override_internal_headers(self, _):
+        """ Test that custom headers override internal SDK headers. """
+        sdk_key = 'some_key'
+        custom_last_modified = 'Custom Last Modified Time'
+        custom_headers = {
+            'If-Modified-Since': custom_last_modified,
+            'X-Custom-Header': 'custom_value'
+        }
+
+        expected_datafile_url = enums.ConfigManager.DATAFILE_URL_TEMPLATE.format(sdk_key=sdk_key)
+        test_headers = {'Last-Modified': 'New Time'}
+        test_datafile = json.dumps(self.config_dict_with_features)
+        test_response = requests.Response()
+        test_response.status_code = 200
+        test_response.headers = test_headers
+        test_response._content = test_datafile
+
+        # First request to set last_modified
+        with mock.patch('requests.Session.get', return_value=test_response):
+            project_config_manager = config_manager.PollingConfigManager(
+                sdk_key=sdk_key,
+                custom_headers=custom_headers
+            )
+            project_config_manager.stop()
+
+        # Second request should use custom header value instead of internal last_modified
+        with mock.patch('requests.Session.get', return_value=test_response) as mock_request:
+            project_config_manager._initialize_thread()
+            project_config_manager.start()
+            project_config_manager.stop()
+
+        # Assert that custom If-Modified-Since header overrides the internal one
+        expected_headers = {
+            'If-Modified-Since': custom_last_modified,  # User's value should be used
+            'X-Custom-Header': 'custom_value'
+        }
+        mock_request.assert_called_once_with(
+            expected_datafile_url,
+            headers=expected_headers,
+            timeout=enums.ConfigManager.REQUEST_TIMEOUT
+        )
+
 
 @mock.patch('requests.Session.get')
 class AuthDatafilePollingConfigManagerTest(base.BaseTest):
@@ -637,3 +711,88 @@ def test_fetch_datafile__request_exception_raised(self, _):
         )
         self.assertEqual(test_headers['Last-Modified'], project_config_manager.last_modified)
         self.assertIsInstance(project_config_manager.get_config(), project_config.ProjectConfig)
+
+    def test_custom_headers(self, _):
+        """ Test that custom headers are included in authenticated datafile fetch requests. """
+        datafile_access_token = 'some_token'
+        sdk_key = 'some_key'
+        custom_headers = {
+            'X-Custom-Header': 'custom_value',
+            'X-Another-Header': 'another_value'
+        }
+
+        with mock.patch('optimizely.config_manager.AuthDatafilePollingConfigManager.fetch_datafile'), mock.patch(
+            'optimizely.config_manager.AuthDatafilePollingConfigManager._run'
+        ):
+            project_config_manager = config_manager.AuthDatafilePollingConfigManager(
+                datafile_access_token=datafile_access_token,
+                sdk_key=sdk_key,
+                custom_headers=custom_headers
+            )
+
+        expected_datafile_url = enums.ConfigManager.AUTHENTICATED_DATAFILE_URL_TEMPLATE.format(sdk_key=sdk_key)
+        test_headers = {'Last-Modified': 'New Time'}
+        test_datafile = json.dumps(self.config_dict_with_features)
+        test_response = requests.Response()
+        test_response.status_code = 200
+        test_response.headers = test_headers
+        test_response._content = test_datafile
+
+        # Call fetch_datafile and assert that request was sent with both authorization and custom headers
+        with mock.patch('requests.Session.get', return_value=test_response) as mock_request:
+            project_config_manager.fetch_datafile()
+
+        expected_headers = {
+            'Authorization': f'Bearer {datafile_access_token}',
+            'X-Custom-Header': 'custom_value',
+            'X-Another-Header': 'another_value'
+        }
+        mock_request.assert_called_once_with(
+            expected_datafile_url,
+            headers=expected_headers,
+            timeout=enums.ConfigManager.REQUEST_TIMEOUT,
+        )
+        self.assertIsInstance(project_config_manager.get_config(), project_config.ProjectConfig)
+
+    def test_custom_headers_override_authorization(self, _):
+        """ Test that custom Authorization header overrides internal SDK authorization header. """
+        datafile_access_token = 'some_token'
+        custom_auth = 'Bearer custom_token'
+        sdk_key = 'some_key'
+        custom_headers = {
+            'Authorization': custom_auth,
+            'X-Custom-Header': 'custom_value'
+        }
+
+        with mock.patch('optimizely.config_manager.AuthDatafilePollingConfigManager.fetch_datafile'), mock.patch(
+            'optimizely.config_manager.AuthDatafilePollingConfigManager._run'
+        ):
+            project_config_manager = config_manager.AuthDatafilePollingConfigManager(
+                datafile_access_token=datafile_access_token,
+                sdk_key=sdk_key,
+                custom_headers=custom_headers
+            )
+
+        expected_datafile_url = enums.ConfigManager.AUTHENTICATED_DATAFILE_URL_TEMPLATE.format(sdk_key=sdk_key)
+        test_headers = {'Last-Modified': 'New Time'}
+        test_datafile = json.dumps(self.config_dict_with_features)
+        test_response = requests.Response()
+        test_response.status_code = 200
+        test_response.headers = test_headers
+        test_response._content = test_datafile
+
+        # Call fetch_datafile and assert that custom Authorization header is used
+        with mock.patch('requests.Session.get', return_value=test_response) as mock_request:
+            project_config_manager.fetch_datafile()
+
+        expected_headers = {
+            'Authorization': custom_auth,  # User's custom auth should override
+            'X-Custom-Header': 'custom_value'
+        }
+        mock_request.assert_called_once_with(
+            expected_datafile_url,
+            headers=expected_headers,
+            timeout=enums.ConfigManager.REQUEST_TIMEOUT,
+        )
+        self.assertIsInstance(project_config_manager.get_config(), project_config.ProjectConfig)
+