update streamlit example to not use tunnels

10_integrations/streamlit/serve_streamlit.py

@@ -4,24 +4,24 @@
 #
 # # Run and share Streamlit apps
 #
-# This example supports running the Streamlit app ephemerally with `modal run`, and
-# deploying a web endpoint from which others can spin up isolated instances of the Streamlit
-# app, each accessible in the browser via URL!
+# This example shows you how to run a Streamlit app with `modal serve`, and then deploy it as a serverless web app.
 #
 # ![example streamlit app](./streamlit.png)
 #
-# The example is structured as two files:
+# This example is structured as two files:
 #
 # 1. This module, which defines the Modal objects (name the script `serve_streamlit.py` locally).
-# 2. `app.py`, which is a Streamlit script and is mounted into a Modal function ([download script](https://github.com/modal-labs/modal-examples/blob/main/10_integrations/streamlit/app.py)).
+# 2. `app.py`, which is any Streamlit script to be mounted into the Modal
+# function ([download script](https://github.com/modal-labs/modal-examples/blob/main/10_integrations/streamlit/app.py)).
+
 import pathlib
 
 import modal
 
 # ## Define container dependencies
 #
 # The `app.py` script imports three third-party packages, so we include these in the example's
-# image definition.
+# image definition. We also install `asgiproxy` to proxy the Streamlit server.
 
 image = (
     modal.Image.debian_slim()
@@ -33,15 +33,29 @@
 
 stub = modal.Stub(name="example-modal-streamlit", image=image)
 
+# ## Mounting the `app.py` script
+#
+# We can just mount the `app.py` script inside the container at a pre-defined path using a Modal
+# [`Mount`](https://modal.com/docs/guide/local-data#mounting-directories).
+
 streamlit_script_local_path = pathlib.Path(__file__).parent / "app.py"
 streamlit_script_remote_path = pathlib.Path("/root/app.py")
 
-# ## Mounting the `app.py` script
-#
-# As the Modal code and Streamlit code are isolated, we can just mount the latter into the container
-# at a configured path, and pass that path to the Streamlit server.
+if not streamlit_script_local_path.exists():
+    raise RuntimeError(
+        "app.py not found! Place the script with your streamlit app in the same directory."
+    )
+
+streamlit_script_mount = modal.Mount.from_local_file(
+    streamlit_script_local_path,
+    streamlit_script_remote_path,
+)
+
+# ## Spawning the Streamlit server
 #
-# We could also import the module, and then pass `app.__path__` to Streamlit.
+# Inside the container, we will run the Streamlit server in a background subprocess using
+# `subprocess.Popen`. Here we define `spawn_server()` to do this and then poll until the server
+# is ready to accept connections.
 
 HOST = "127.0.0.1"
 PORT = "8000"
@@ -83,13 +97,17 @@ def spawn_server():
                 )
 
 
-streamlit_script_mount = modal.Mount.from_local_file(
-    streamlit_script_local_path,
-    streamlit_script_remote_path,
-)
+# ## Wrap it in an ASGI app
+#
+# Finally, Modal can only serve apps that speak the [ASGI](https://modal.com/docs/guide/webhooks#asgi) or
+# [WSGI](https://modal.com/docs/guide/webhooks#wsgi) protocols. Since the Streamlit server is neither,
+# we run a separate ASGI app that proxies requests to the Streamlit server using the `asgiproxy` package.
+# Note that at this point `asgiproxy` has a bug with websocket handling, so we are using a
+# [fork](https://github.com/modal-labs/asgiproxy) with the fix for this.
 
 
 @stub.function(
+    # Allows 100 concurrent requests per container.
     allow_concurrent_inputs=100,
     mounts=[streamlit_script_mount],
 )
@@ -111,3 +129,22 @@ def run():
     )()
     proxy_context = ProxyContext(config)
     return make_simple_proxy_app(proxy_context)
+
+
+# ## Iterate and Deploy
+#
+# While you're iterating on your screamlit app, you can run it "ephemerally" with `modal serve`. This will
+# run a local process that watches your files and updates the app if anything changes.
+#
+# ```shell
+# modal serve serve_streamlit.py
+# ```
+#
+# Once you're happy with your changes, you can deploy your application with
+#
+# ```shell
+# modal deploy serve_streamlit.py
+# ```
+#
+# If successful, this will print a URL for your app, that you can navigate to from
+# your browser 🎉 .