include conditional MyApp proxy for dash

app/my_app.py

+import sys 
+sys.path.append("/home/jovyan/")
+
+import argparse
+import logging
+
+from urllib.parse import urlparse, urljoin
+
+from dash import Dash
+
+from jupyter_server.serverapp import list_running_servers
+
+try: 
+    from my_layout import layout
+    from my_callbacks import register_callbacks
+except ModuleNotFoundError:
+    # do not let Dash start
+    exit()
+
+
+logging.basicConfig(level=logging.INFO)
+
+# weird trick to find base_url for the jupyterlab
+def find_jupyterlab_base_url():
+    servers = list_running_servers()
+    for server in servers:
+        if server["port"] == 8888:
+            return server['url']
+    return None
+
+
+# get the correct port from proxy
+parser = argparse.ArgumentParser()
+parser.add_argument("--port", type=int)
+args = parser.parse_args()
+port: int = args.port
+
+if not port:
+    raise ValueError(f"Port of proxy server for Dash not found in {args}.")
+else: 
+    logging.debug(f"Dash app running on port {port}.")
+
+
+base_url = find_jupyterlab_base_url()
+if base_url is None:
+    raise ValueError("Base URL of Jupyterlab could not be detected.")
+logging.debug(f"Base URL: {base_url}")
+
+proxy_base_path = urlparse(urljoin(base_url + "/", f"proxy/{port}/")).path
+logging.debug(f"Proxy base path: {proxy_base_path}")
+
+# define Dash app
+app = Dash(
+    name=__name__, 
+    requests_pathname_prefix=proxy_base_path
+)
+
+# define layout
+app.layout = layout
+
+# register all callback functions
+register_callbacks(app=app)
+
+# Run Dash app in the notebook
+app.run(
+    jupyter_mode="jupyterlab", 
+    port=port, 
+    host="0.0.0.0",
+    debug=True
+)

dash_proxy/my_app_proxy.py

+def setup_my_app_proxy():
+    command = [
+        'python',
+        '/dash/app/my_app.py',
+        '--port',
+        '{port}'
+    ]
+    
+    return {
+        "command": command,
+        "new_browser_tab": False,
+        "launcher_entry": {
+            "enabled": True,
+            'title': 'MyApp'
+        }
+    }

dash_proxy/setup.py

@@ -5,11 +5,12 @@ setuptools.setup(
     author_email="julian.rasch@fh-muenster.de",
     description="A small module to run Dash inside a dockerized Jupyterlab.",
     name="jupyter-dash-proxy",
-    py_modules=["dash_proxy"],
+    py_modules=["dash_proxy", "my_app_proxy"],
     entry_points={
         "jupyter_serverproxy_servers": [
             # name = packagename:function_name
             "Dash = dash_proxy:setup_dash_proxy",
+            "MyApp = my_app_proxy:setup_my_app_proxy"
         ]
     },
     install_requires=["jupyter-server-proxy==4.0.0"],