allow different internal and public hub_url

binderhub/app.py

@@ -352,7 +352,15 @@ def _default_hub_token(self):
         """,
         config=True,
     )
-    @validate('hub_url')
+
+    hub_url_public = Unicode(
+        help="""
+        The public base URL of the JupyterHub instance where users will run if different from hub_url
+        """,
+        config=True,
+    )
+
+    @validate('hub_url', 'hub_url_public')
     def _add_slash(self, proposal):
         """trait validator to ensure hub_url ends with a trailing slash"""
         if proposal.value is not None and not proposal.value.endswith('/'):
@@ -549,6 +557,7 @@ def initialize(self, *args, **kwargs):
         self.launcher = Launcher(
             parent=self,
             hub_url=self.hub_url,
+            hub_url_public=self.hub_url_public,
             hub_api_token=self.hub_api_token,
             create_user=not self.auth_enabled,
         )

binderhub/launcher.py

@@ -32,6 +32,7 @@ class Launcher(LoggingConfigurable):
 
     hub_api_token = Unicode(help="The API token for the Hub")
     hub_url = Unicode(help="The URL of the Hub")
+    hub_url_public = Unicode(help="The public URL of the Hub if different")
     create_user = Bool(True, help="Create a new Hub user")
     retries = Integer(
         4,
@@ -196,5 +197,5 @@ async def launch(self, image, username, server_name='', repo_url=''):
                           format(_server_name, username, e, body))
             raise web.HTTPError(500, "Failed to launch image %s" % image)
 
-        data['url'] = self.hub_url + 'user/%s/%s' % (username, server_name)
+        data['url'] = (self.hub_url_public or self.hub_url) + 'user/%s/%s' % (username, server_name)
         return data