feat: add SIGTERM handling and update typer dependency (#4548)

* Update `typer` dependency to version 0.13.0 in `pyproject.toml`

* refactor: Simplify exception handling in the CLI

* Enhance lifespan function with clean shutdown and logging improvements

* Add graceful shutdown handling for SIGTERM and SIGINT signals

- Introduce signal handlers to manage SIGTERM and SIGINT for graceful server shutdown.
- Update exception handling to ensure processes terminate properly and log shutdown events.
- Modify server run logic to support signal-based shutdowns, improving reliability.

---------

Co-authored-by: Nadir J <31660040+NadirJ@users.noreply.github.com>

src/backend/base/langflow/__main__.py

@@ -1,6 +1,7 @@
 import asyncio
 import inspect
 import platform
+import signal
 import socket
 import sys
 import time
@@ -24,9 +25,7 @@ from sqlmodel import select
 
 from langflow.logging.logger import configure, logger
 from langflow.main import setup_app
-from langflow.services.database.models.folder.utils import (
-    create_default_folder_if_it_doesnt_exist,
-)
+from langflow.services.database.models.folder.utils import create_default_folder_if_it_doesnt_exist
 from langflow.services.database.utils import session_getter
 from langflow.services.deps import async_session_scope, get_db_service, get_settings_service
 from langflow.services.settings.constants import DEFAULT_SUPERUSER
@@ -77,6 +76,13 @@ def set_var_for_macos_issue() -> None:
         logger.debug("Set OBJC_DISABLE_INITIALIZE_FORK_SAFETY to YES to avoid error")
 
 
+def handle_sigterm(signum, frame):  # noqa: ARG001
+    """Handle SIGTERM signal gracefully."""
+    logger.info("Received SIGTERM signal. Performing graceful shutdown...")
+    # Raise SystemExit to trigger graceful shutdown
+    sys.exit(0)
+
+
 @app.command()
 def run(
     *,
@@ -150,6 +156,9 @@ def run(
     ),
 ) -> None:
     """Run Langflow."""
+    # Register SIGTERM handler
+    signal.signal(signal.SIGTERM, handle_sigterm)
+
     if env_file:
         load_dotenv(env_file, override=True)
 
@@ -211,13 +220,20 @@ def run(
             click.launch(f"http://{host}:{port}")
         if process:
             process.join()
-    except KeyboardInterrupt:
+    except (KeyboardInterrupt, SystemExit) as e:
+        logger.info("Shutting down server...")
         if process is not None:
             process.terminate()
-        sys.exit(0)
-    except Exception as e:  # noqa: BLE001
+            process.join(timeout=15)  # Wait up to 15 seconds for process to terminate
+            if process.is_alive():
+                logger.warning("Process did not terminate gracefully, forcing...")
+                process.kill()
+        raise typer.Exit(0) from e
+    except Exception as e:
         logger.exception(e)
-        sys.exit(1)
+        if process is not None:
+            process.terminate()
+        raise typer.Exit(1) from e
 
 
 def wait_for_server_ready(host, port) -> None:
@@ -359,9 +375,6 @@ def print_banner(host: str, port: int) -> None:
 def run_langflow(host, port, log_level, options, app) -> None:
     """Run Langflow server on localhost."""
     if platform.system() == "Windows":
-        # Run using uvicorn on MacOS and Windows
-        # Windows doesn't support gunicorn
-        # MacOS requires an env variable to be set to use gunicorn
         import uvicorn
 
         uvicorn.run(
@@ -374,7 +387,28 @@ def run_langflow(host, port, log_level, options, app) -> None:
     else:
         from langflow.server import LangflowApplication
 
-        LangflowApplication(app, options).run()
+        server = LangflowApplication(app, options)
+
+        def graceful_shutdown(signum, frame):  # noqa: ARG001
+            """Gracefully shutdown the server when receiving SIGTERM."""
+            # Suppress click exceptions during shutdown
+            import click
+
+            click.echo = lambda *args, **kwargs: None  # noqa: ARG005
+
+            logger.info("Gracefully shutting down server...")
+            # For Gunicorn workers, we raise SystemExit to trigger graceful shutdown
+            raise SystemExit(0)
+
+        # Register signal handlers
+        signal.signal(signal.SIGTERM, graceful_shutdown)
+        signal.signal(signal.SIGINT, graceful_shutdown)
+
+        try:
+            server.run()
+        except (KeyboardInterrupt, SystemExit):
+            # Suppress the exception output
+            sys.exit(0)
 
 
 @app.command()
@@ -499,10 +533,7 @@ def api_key(
                 )
                 return None
             from langflow.services.database.models.api_key import ApiKey, ApiKeyCreate
-            from langflow.services.database.models.api_key.crud import (
-                create_api_key,
-                delete_api_key,
-            )
+            from langflow.services.database.models.api_key.crud import create_api_key, delete_api_key
 
             api_key = (await session.exec(select(ApiKey).where(ApiKey.user_id == superuser.id))).first()
             if api_key:
@@ -568,4 +599,8 @@ def main() -> None:
 
 
 if __name__ == "__main__":
-    main()
+    try:
+        main()
+    except Exception as e:
+        logger.exception(e)
+        raise typer.Exit(1) from e

src/backend/base/langflow/main.py

@@ -97,6 +97,7 @@ def get_lifespan(*, fix_migration=False, version=None):
     @asynccontextmanager
     async def lifespan(_app: FastAPI):
         configure(async_file=True)
+
         # Startup message
         if version:
             rprint(f"[bold green]Starting Langflow v{version}...[/bold green]")
@@ -108,15 +109,20 @@ def get_lifespan(*, fix_migration=False, version=None):
             await asyncio.to_thread(create_or_update_starter_projects, all_types_dict)
             telemetry_service.start()
             await asyncio.to_thread(load_flows_from_directory)
+
             yield
+
         except Exception as exc:
             if "langflow migration --fix" not in str(exc):
                 logger.exception(exc)
             raise
-        # Shutdown message
-        rprint("[bold red]Shutting down Langflow...[/bold red]")
-        await teardown_services()
-        await logger.complete()
+        finally:
+            # Clean shutdown
+            logger.info("Cleaning up resources...")
+            await teardown_services()
+            await logger.complete()
+            # Final message
+            rprint("[bold red]Langflow shutdown complete[/bold red]")
 
     return lifespan
 

src/backend/base/pyproject.toml

@@ -119,7 +119,7 @@ dependencies = [
     "langchain-experimental>=0.0.61",
     "pydantic>=2.7.0",
     "pydantic-settings>=2.2.0",
-    "typer>=0.12.0",
+    "typer>=0.13.0",
     "cachetools>=5.3.1",
     "platformdirs>=4.2.0",
     "python-multipart>=0.0.12",