[Feature] Introduce new Credential Strategies for Agents

databricks/sdk/credentials_provider.py

@@ -9,6 +9,7 @@
 import platform
 import subprocess
 import sys
+import threading
 import time
 from datetime import datetime
 from typing import Callable, Dict, List, Optional, Tuple, Union
@@ -723,14 +724,17 @@ def inner() -> Dict[str, str]:
 # This Code is derived from Mlflow DatabricksModelServingConfigProvider
 # https://github.com/mlflow/mlflow/blob/1219e3ef1aac7d337a618a352cd859b336cf5c81/mlflow/legacy_databricks_cli/configure/provider.py#L332
 class ModelServingAuthProvider():
+    USER_CREDENTIALS = "user_credentials"
+
     _MODEL_DEPENDENCY_OAUTH_TOKEN_FILE_PATH = "/var/credentials-secret/model-dependencies-oauth-token"
 
-    def __init__(self):
+    def __init__(self, credential_type: Optional[str]):
         self.expiry_time = -1
         self.current_token = None
         self.refresh_duration = 300 # 300 Seconds
+        self.credential_type = credential_type
 
-    def should_fetch_model_serving_environment_oauth(self) -> bool:
+    def should_fetch_model_serving_environment_oauth() -> bool:
         """
         Check whether this is the model serving environment
         Additionally check if the oauth token file path exists
@@ -739,15 +743,15 @@ def should_fetch_model_serving_environment_oauth(self) -> bool:
         is_in_model_serving_env = (os.environ.get("IS_IN_DB_MODEL_SERVING_ENV")
                                    or os.environ.get("IS_IN_DATABRICKS_MODEL_SERVING_ENV") or "false")
         return (is_in_model_serving_env == "true"
-                and os.path.isfile(self._MODEL_DEPENDENCY_OAUTH_TOKEN_FILE_PATH))
+                and os.path.isfile(ModelServingAuthProvider._MODEL_DEPENDENCY_OAUTH_TOKEN_FILE_PATH))
 
-    def get_model_dependency_oauth_token(self, should_retry=True) -> str:
+    def _get_model_dependency_oauth_token(self, should_retry=True) -> str:
         # Use Cached value if it is valid
         if self.current_token is not None and self.expiry_time > time.time():
             return self.current_token
 
         try:
-            with open(self._MODEL_DEPENDENCY_OAUTH_TOKEN_FILE_PATH) as f:
+            with open(ModelServingAuthProvider._MODEL_DEPENDENCY_OAUTH_TOKEN_FILE_PATH) as f:
                 oauth_dict = json.load(f)
                 self.current_token = oauth_dict["OAUTH_TOKEN"][0]["oauthTokenValue"]
                 self.expiry_time = time.time() + self.refresh_duration
@@ -757,32 +761,43 @@ def get_model_dependency_oauth_token(self, should_retry=True) -> str:
                 logger.warning("Unable to read oauth token on first attmept in Model Serving Environment",
                                exc_info=e)
                 time.sleep(0.5)
-                return self.get_model_dependency_oauth_token(should_retry=False)
+                return self._get_model_dependency_oauth_token(should_retry=False)
             else:
                 raise RuntimeError(
                     "Unable to read OAuth credentials from the file mounted in Databricks Model Serving"
                 ) from e
         return self.current_token
 
+    def _get_invokers_token(self):
+        current_thread = threading.current_thread()
+        thread_data = current_thread.__dict__
+        invokers_token = None
+        if "invokers_token" in thread_data:
+            invokers_token = thread_data["invokers_token"]
+
+        if invokers_token is None:
+            raise RuntimeError("Unable to read Invokers Token in Databricks Model Serving")
+
+        return invokers_token
+
     def get_databricks_host_token(self) -> Optional[Tuple[str, str]]:
-        if not self.should_fetch_model_serving_environment_oauth():
+        if not ModelServingAuthProvider.should_fetch_model_serving_environment_oauth():
             return None
 
         # read from DB_MODEL_SERVING_HOST_ENV_VAR if available otherwise MODEL_SERVING_HOST_ENV_VAR
         host = os.environ.get("DATABRICKS_MODEL_SERVING_HOST_URL") or os.environ.get(
             "DB_MODEL_SERVING_HOST_URL")
-        token = self.get_model_dependency_oauth_token()
 
-        return (host, token)
+        if self.credential_type == ModelServingAuthProvider.USER_CREDENTIALS:
+            return (host, self._get_invokers_token())
+        else:
+            return (host, self._get_model_dependency_oauth_token())
 
 
-@credentials_strategy('model-serving', [])
-def model_serving_auth(cfg: 'Config') -> Optional[CredentialsProvider]:
+def model_serving_auth_visitor(cfg: 'Config',
+                               credential_type: Optional[str] = None) -> Optional[CredentialsProvider]:
     try:
-        model_serving_auth_provider = ModelServingAuthProvider()
-        if not model_serving_auth_provider.should_fetch_model_serving_environment_oauth():
-            logger.debug("model-serving: Not in Databricks Model Serving, skipping")
-            return None
+        model_serving_auth_provider = ModelServingAuthProvider(credential_type)
         host, token = model_serving_auth_provider.get_databricks_host_token()
         if token is None:
             raise ValueError(
@@ -793,7 +808,6 @@ def model_serving_auth(cfg: 'Config') -> Optional[CredentialsProvider]:
     except Exception as e:
         logger.warning("Unable to get auth from Databricks Model Serving Environment", exc_info=e)
         return None
-
     logger.info("Using Databricks Model Serving Authentication")
 
     def inner() -> Dict[str, str]:
@@ -804,6 +818,15 @@ def inner() -> Dict[str, str]:
     return inner
 
 
+@credentials_strategy('model-serving', [])
+def model_serving_auth(cfg: 'Config') -> Optional[CredentialsProvider]:
+    if not ModelServingAuthProvider.should_fetch_model_serving_environment_oauth():
+        logger.debug("model-serving: Not in Databricks Model Serving, skipping")
+        return None
+
+    return model_serving_auth_visitor(cfg)
+
+
 class DefaultCredentials:
     """ Select the first applicable credential provider from the chain """
 
@@ -846,3 +869,35 @@ def __call__(self, cfg: 'Config') -> CredentialsProvider:
         raise ValueError(
             f'cannot configure default credentials, please check {auth_flow_url} to configure credentials for your preferred authentication method.'
         )
+
+
+class ModelServingUserCredentials(CredentialsStrategy):
+    """
+    This credential strategy is designed for authenticating the Databricks SDK in the model serving environment using user-specific rights. 
+    In the model serving environment, the strategy retrieves a downscoped user token from the thread-local variable. 
+    In any other environments, the class defaults to the DefaultCredentialStrategy. 
+    To use this credential strategy, instantiate the WorkspaceClient with the ModelServingUserCredentials strategy as follows:
+
+    invokers_client = WorkspaceClient(credential_strategy = ModelServingUserCredentials())
+    """
+
+    def __init__(self):
+        self.credential_type = ModelServingAuthProvider.USER_CREDENTIALS
+        self.default_credentials = DefaultCredentials()
+
+    def auth_type(self):
+        if ModelServingAuthProvider.should_fetch_model_serving_environment_oauth():
+            return "model_serving_" + self.credential_type
+        else:
+            return self.default_credentials.auth_type()
+
+    def __call__(self, cfg: 'Config') -> CredentialsProvider:
+        if ModelServingAuthProvider.should_fetch_model_serving_environment_oauth():
+            header_factory = model_serving_auth_visitor(cfg, self.credential_type)
+            if not header_factory:
+                raise ValueError(
+                    f"Unable to authenticate using {self.credential_type} in Databricks Model Serving Environment"
+                )
+            return header_factory
+        else:
+            return self.default_credentials(cfg)

tests/test_model_serving_auth.py

@@ -1,8 +1,10 @@
+import threading
 import time
 
 import pytest
 
 from databricks.sdk.core import Config
+from databricks.sdk.credentials_provider import ModelServingUserCredentials
 
 from .conftest import raises
 
@@ -39,7 +41,6 @@ def test_model_serving_auth(env_values, del_env_values, oauth_file_name, monkeyp
     mocker.patch('databricks.sdk.config.Config._known_file_config_loader')
 
     cfg = Config()
-
     assert cfg.auth_type == 'model-serving'
     headers = cfg.authenticate()
     assert (cfg.host == 'x')
@@ -93,7 +94,6 @@ def test_model_serving_auth_refresh(monkeypatch, mocker):
     assert (cfg.host == 'x')
     assert headers.get(
         "Authorization") == 'Bearer databricks_sdk_unit_test_token' # Token defined in the test file
-
     # Simulate refreshing the token by patching to to a new file
     monkeypatch.setattr(
         "databricks.sdk.credentials_provider.ModelServingAuthProvider._MODEL_DEPENDENCY_OAUTH_TOKEN_FILE_PATH",
@@ -113,3 +113,49 @@ def test_model_serving_auth_refresh(monkeypatch, mocker):
     assert (cfg.host == 'x')
     # Read V2 now
     assert headers.get("Authorization") == 'Bearer databricks_sdk_unit_test_token_v2'
+
+
+def test_agent_user_credentials(monkeypatch, mocker):
+    monkeypatch.setenv('IS_IN_DB_MODEL_SERVING_ENV', 'true')
+    monkeypatch.setenv('DB_MODEL_SERVING_HOST_URL', 'x')
+    monkeypatch.setattr(
+        "databricks.sdk.credentials_provider.ModelServingAuthProvider._MODEL_DEPENDENCY_OAUTH_TOKEN_FILE_PATH",
+        "tests/testdata/model-serving-test-token")
+
+    invokers_token_val = "databricks_invokers_token"
+    current_thread = threading.current_thread()
+    thread_data = current_thread.__dict__
+    thread_data["invokers_token"] = invokers_token_val
+
+    cfg = Config(credentials_strategy=ModelServingUserCredentials())
+    assert cfg.auth_type == 'model_serving_user_credentials'
+
+    headers = cfg.authenticate()
+
+    assert (cfg.host == 'x')
+    assert headers.get("Authorization") == f'Bearer {invokers_token_val}'
+
+    # Test updates of invokers token
+    invokers_token_val = "databricks_invokers_token_v2"
+    current_thread = threading.current_thread()
+    thread_data = current_thread.__dict__
+    thread_data["invokers_token"] = invokers_token_val
+
+    headers = cfg.authenticate()
+    assert (cfg.host == 'x')
+    assert headers.get("Authorization") == f'Bearer {invokers_token_val}'
+
+
+# If this credential strategy is being used in a non model serving environments then use default credential strategy instead
+def test_agent_user_credentials_in_non_model_serving_environments(monkeypatch):
+
+    monkeypatch.setenv('DATABRICKS_HOST', 'x')
+    monkeypatch.setenv('DATABRICKS_TOKEN', 'token')
+
+    cfg = Config(credentials_strategy=ModelServingUserCredentials())
+    assert cfg.auth_type == 'pat' # Auth type is PAT as it is no longer in a model serving environment
+
+    headers = cfg.authenticate()
+
+    assert (cfg.host == 'https://x')
+    assert headers.get("Authorization") == f'Bearer token'