feat: add sigterm handler to gracefully shutdown worker and log

Author: YunchuWang

azure_functions_worker/logging.py

@@ -91,6 +91,9 @@ def enable_console_logging() -> None:
     if logger and handler:
         logger.addHandler(handler)
 
+def flush_logger(logger: logging.Logger):
+    for handler in logger.handlers:
+        handler.flush()
 
 def is_system_log_category(ctg: str) -> bool:
     """Check if the logging namespace belongs to system logs. Category starts

azure_functions_worker/main.py

@@ -47,12 +47,16 @@ def main():
 
     import asyncio
 
+
     from . import logging
     from .logging import error_logger, format_exception, logger
 
     args = parse_args()
     logging.setup(log_level=args.log_level, log_destination=args.log_to)
 
+    # register sigterm handler
+    register_sigterm_handler()
+
     logger.info('Starting Azure Functions Python Worker.')
     logger.info('Worker ID: %s, Request ID: %s, Host Address: %s:%s',
                 args.worker_id, args.request_id, args.host, args.port)
@@ -66,6 +70,46 @@ def main():
                 format_exception(ex)))
         raise
 
+def register_sigterm_handler():
+    import signal
+    """
+    Registers a custom handler for the SIGTERM signal.
+
+    This function will set up a signal handler to intercept the SIGTERM signal,
+    which is typically sent to gracefully terminate a process. When SIGTERM is
+    received, the program will log the signal and perform a graceful shutdown
+    by calling sys.exit().
+
+    Windows Python Function is not supported and Windows does not support
+    SIGTERM.
+    """
+
+    def handle_sigterm(signum, frame):
+        from . import dispatcher
+        import sys
+        from .logging import logger, flush_logger
+        import traceback
+        from azure_functions_worker.dispatcher import DispatcherMeta
+        from azure_functions_worker import loader
+        # Log the received signal
+        logger.info(f"SIGTERM received (signal: {signum}). "
+                    "Shutting down gracefully...")
+        
+        # Log the frame details to see whats executed when the signal was received
+        logger.info("Frame details at signal receipt:"
+                     f"\n{''.join(traceback.format_stack(frame))}")
+
+        DispatcherMeta.__current_dispatcher__ = None
+
+        loader.uninstall()
+
+        flush_logger()
+
+        dispatcher.Dispatcher.stop()
+        sys.exit(0)  # Exit the program gracefully
+
+    signal.signal(signal.SIGTERM, handle_sigterm)
+
 
 async def start_async(host, port, worker_id, request_id):
     from . import dispatcher