Modal run timestamps (#3882)

* Add --timestamps flag to modal run, serve and deploy

This adds support for the same --timestamps flag that exists in
`modal app logs` to the `modal run` command. When enabled, each
log line from stdout/stderr will be prefixed with a timestamp.

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>

Author: freider

modal/_output.py

@@ -169,9 +169,9 @@ def get(cls) -> OutputManager | None:
 
     @classmethod
     @contextlib.contextmanager
-    def enable_output(cls, show_progress: bool = True) -> Generator[None]:
+    def enable_output(cls, show_progress: bool = True, show_timestamps: bool = False) -> Generator[None]:
         if show_progress:
-            cls._instance = OutputManager()
+            cls._instance = OutputManager(show_timestamps=show_timestamps)
         try:
             yield
         finally:

modal/cli/run.py

@@ -185,7 +185,8 @@ def f(ctx, **kwargs):
         _validate_interactive_quiet_params(ctx)
 
         show_progress: bool = ctx.obj["show_progress"]
-        with enable_output(show_progress):
+        show_timestamps: bool = ctx.obj["show_timestamps"]
+        with enable_output(show_progress, show_timestamps=show_timestamps):
             with run_app(
                 app,
                 detach=ctx.obj["detach"],
@@ -314,7 +315,8 @@ def f(ctx, *args, **kwargs):
         _validate_interactive_quiet_params(ctx)
 
         show_progress: bool = ctx.obj["show_progress"]
-        with enable_output(show_progress):
+        show_timestamps: bool = ctx.obj["show_timestamps"]
+        with enable_output(show_progress, show_timestamps=show_timestamps):
             with run_app(
                 app,
                 detach=ctx.obj["detach"],
@@ -404,8 +406,9 @@ def get_command(self, ctx, func_ref):
 @click.option("-i", "--interactive", is_flag=True, help="Run the app in interactive mode.")
 @click.option("-e", "--env", help=ENV_OPTION_HELP, default=None)
 @click.option("-m", is_flag=True, help="Interpret argument as a Python module path instead of a file/script path")
+@click.option("--timestamps", is_flag=True, help="Show timestamps for each log line.")
 @click.pass_context
-def run(ctx, write_result, detach, quiet, interactive, env, m):
+def run(ctx, write_result, detach, quiet, interactive, env, m, timestamps):
     """Run a Modal function or local entrypoint.
 
     `FUNC_REF` should be of the format `{file or module}::{function name}`.
@@ -442,6 +445,7 @@ def run(ctx, write_result, detach, quiet, interactive, env, m):
     ctx.obj["detach"] = detach  # if subcommand would be a click command...
     ctx.obj["show_progress"] = False if quiet else True
     ctx.obj["interactive"] = interactive
+    ctx.obj["show_timestamps"] = timestamps
 
 
 def deploy(
@@ -453,6 +457,7 @@ def deploy(
     use_module_mode: bool = typer.Option(
         False, "-m", help="Interpret argument as a Python module path instead of a file/script path"
     ),
+    timestamps: bool = typer.Option(False, "--timestamps", help="Show timestamps for each log line."),
 ):
     """Deploy a Modal application.
 
@@ -477,11 +482,11 @@ def deploy(
             "modal deploy ... --name=some-name"
         )
 
-    with enable_output():
+    with enable_output(show_timestamps=timestamps):
         res = deploy_app(app, name=name, environment_name=env or "", tag=tag)
 
     if stream_logs:
-        stream_app_logs(app_id=res.app_id, app_logs_url=res.app_logs_url)
+        stream_app_logs(app_id=res.app_id, app_logs_url=res.app_logs_url, show_timestamps=timestamps)
 
 
 def serve(
@@ -491,6 +496,7 @@ def serve(
     use_module_mode: bool = typer.Option(
         False, "-m", help="Interpret argument as a Python module path instead of a file/script path"
     ),
+    timestamps: bool = typer.Option(False, "--timestamps", help="Show timestamps for each log line."),
 ):
     """Run a web endpoint(s) associated with a Modal app and hot-reload code.
 
@@ -512,7 +518,7 @@ def serve(
     if app.description is None:
         app.set_description(_get_clean_app_description(app_ref))
 
-    with enable_output():
+    with enable_output(show_timestamps=timestamps):
         with serve_app(app, import_ref, environment_name=env):
             if timeout is None:
                 timeout = config["serve_timeout"]

modal/output.py

@@ -19,7 +19,7 @@
 
 
 @contextlib.contextmanager
-def enable_output(show_progress: bool = True) -> Generator[None, None, None]:
+def enable_output(show_progress: bool = True, show_timestamps: bool = False) -> Generator[None, None, None]:
     """Context manager that enable output when using the Python SDK.
 
     This will print to stdout and stderr things such as
@@ -47,7 +47,7 @@ def enable_output(show_progress: bool = True) -> Generator[None, None, None]:
     global OUTPUT_ENABLED
 
     try:
-        with OutputManager.enable_output(show_progress):
+        with OutputManager.enable_output(show_progress, show_timestamps=show_timestamps):
             OUTPUT_ENABLED = True
             yield
     finally:

test/cli_test.py

@@ -558,6 +558,43 @@ async def app_done(self, stream):
     )
 
 
+def test_run_timestamps(servicer, server_url_env, set_env_client, test_dir, monkeypatch):
+    from datetime import timezone
+
+    # Use a known timestamp (2025-01-15 12:00:45 UTC)
+    known_timestamp = 1736942445.0
+
+    # Mock locale_tz to return UTC for predictable timestamp formatting
+    monkeypatch.setattr("modal._utils.time_utils.locale_tz", lambda: timezone.utc)
+
+    async def app_logs_with_timestamp(self, stream):
+        await stream.recv_message()
+        log = api_pb2.TaskLogs(
+            data="test log message\n",
+            file_descriptor=api_pb2.FILE_DESCRIPTOR_STDOUT,
+            timestamp=known_timestamp,
+        )
+        await stream.send_message(api_pb2.TaskLogsBatch(entry_id="1", items=[log]))
+        await stream.send_message(api_pb2.TaskLogsBatch(app_done=True))
+
+    with servicer.intercept() as ctx:
+        ctx.set_responder("AppGetLogs", app_logs_with_timestamp)
+
+        app_file = test_dir / "supports" / "app_run_tests" / "default_app.py"
+
+        # Test without --timestamps flag - should not include timestamp
+        res = run_cli_command(["run", app_file.as_posix()])
+        assert "test log message" in res.stdout
+        # The timestamp string format is "YYYY-MM-DD HH:MM:SS+TZ" - check that it's NOT there
+        assert "2025-01-15 12:00:45" not in res.stdout
+
+        # Test with --timestamps flag - should include timestamp prefix
+        res = run_cli_command(["run", "--timestamps", app_file.as_posix()])
+        # Check for the full formatted line: "YYYY-MM-DD HH:MM:SS+00:00 <message>"
+        expected_line = "2025-01-15 12:00:45+00:00 test log message"
+        assert expected_line in res.stdout
+
+
 def test_app_stop(servicer, mock_dir, set_env_client):
     with mock_dir({"myapp.py": dummy_app_file, "other_module.py": dummy_other_module_file}):
         # Deploy as a module