Replace traceback.print_exc() with logger.exception() for proper logging (#160)

Using traceback.print_exc() and traceback.print_exception() writes directly
to stderr, bypassing the Python logging system. This prevents users from:
- Configuring log destinations (files, syslog, cloud services)
- Controlling log levels and filtering
- Using structured logging formats (JSON, etc.)
- Integrating with monitoring and alerting systems

PEP 337 explicitly recommends: "Replace traceback.print_exception with
_log.exception" and states that modules should "use the logging system
instead of print or sys.stdout.write."

Changes:
- Added logging.getLogger(__name__) to server.py and server_context.py
- Replaced traceback.print_exc() with logger.exception() in 2 locations
- Replaced traceback.print_exception() with logger.exception() in 2 locations

This allows applications using the SDK to properly control exception logging
through standard Python logging configuration.

References:
- PEP 337: https://peps.python.org/pep-0337/
- Python Logging HOWTO: https://docs.python.org/3/howto/logging.html

Author: Gustavo-Hagenbeck

python/restate/server.py

@@ -11,8 +11,8 @@
 """This module contains the ASGI server for the restate framework."""
 
 import asyncio
+import logging
 from typing import Dict, TypedDict, Literal
-import traceback
 
 from restate.discovery import compute_discovery_json
 from restate.endpoint import Endpoint
@@ -24,6 +24,8 @@
 from restate._internal import PyIdentityVerifier, IdentityVerificationException  # pylint: disable=import-error,no-name-in-module
 from restate._internal import SDK_VERSION  # pylint: disable=import-error,no-name-in-module
 
+logger = logging.getLogger(__name__)
+
 X_RESTATE_SERVER = header_to_binary([("x-restate-server", f"restate-sdk-python/{SDK_VERSION}")])
 
 
@@ -165,7 +167,7 @@ async def process_invocation_to_completion(
         return
     # pylint: disable=W0718
     except Exception:
-        traceback.print_exc()
+        logger.exception("Exception in Restate handler")
     try:
         await context.leave()
     finally:
@@ -272,7 +274,7 @@ async def app(scope: Scope, receive: Receive, send: Send):
         except LifeSpanNotImplemented as e:
             raise e
         except Exception as e:
-            traceback.print_exc()
+            logger.exception("Exception in ASGI app")
             raise e
 
     if is_running_on_lambda():

python/restate/server_context.py

@@ -24,6 +24,7 @@
 from datetime import timedelta
 import inspect
 import functools
+import logging
 from typing import Any, Awaitable, Callable, Dict, List, Optional, TypeVar, Union, Coroutine
 import typing
 import traceback
@@ -59,6 +60,7 @@
     DoWaitPendingRun,
 )
 
+logger = logging.getLogger(__name__)
 
 T = TypeVar("T")
 I = TypeVar("I")
@@ -448,8 +450,7 @@ async def must_take_notification(self, handle):
         if isinstance(res, Exception):
             # We might need to write out something at this point.
             await self.take_and_send_output()
-            # Print this exception, might be relevant for the user
-            traceback.print_exception(res)
+            logger.exception("Exception in take_notification", exc_info=res)
             raise SdkInternalException() from res
         if isinstance(res, Suspended):
             # We might need to write out something at this point.
@@ -469,8 +470,7 @@ async def create_poll_or_cancel_coroutine(self, handles: typing.List[int]) -> No
             await self.take_and_send_output()
             do_progress_response = self.vm.do_progress(handles)
             if isinstance(do_progress_response, BaseException):
-                # Print this exception, might be relevant for the user
-                traceback.print_exception(do_progress_response)
+                logger.exception("Exception in do_progress", exc_info=do_progress_response)
                 raise SdkInternalException() from do_progress_response
             if isinstance(do_progress_response, Suspended):
                 raise SuspendedException()