Work/fix firewall for localhost (#8868)

Co-authored-by: Hendrik Makait <hendrik@makait.com>

distributed/deploy/local.py

@@ -62,6 +62,9 @@ class LocalCluster(SpecCluster):
         'localhost:8787' or '0.0.0.0:8787'.  Defaults to ':8787'.
         Set to ``None`` to disable the dashboard.
         Use ':0' for a random port.
+        When specifying only a port like ':8787', the dashboard will bind to the given interface from the ``host`` parameter.
+        If ``host`` is empty, binding will occur on all interfaces '0.0.0.0'.
+        To avoid firewall issues when deploying locally, set ``host`` to 'localhost'.
     worker_dashboard_address: str
         Address on which to listen for the Bokeh worker diagnostics server like
         'localhost:8787' or '0.0.0.0:8787'.  Defaults to None which disables the dashboard.

distributed/node.py

@@ -143,9 +143,14 @@ def start_http_server(
         self.http_server = HTTPServer(self.http_application, ssl_options=ssl_options)
 
         http_addresses = clean_dashboard_address(dashboard_address or default_port)
-
         for http_address in http_addresses:
-            if http_address["address"] is None:
+            # Handle default case for dashboard address
+            # In case dashboard_address is given, e.g. ":8787"
+            # the address is empty and it is intended to listen to all interfaces
+            if dashboard_address is not None and http_address["address"] == "":
+                http_address["address"] = "0.0.0.0"
+
+            if http_address["address"] is None or http_address["address"] == "":
                 address = self._start_address
                 if isinstance(address, (list, tuple)):
                     address = address[0]

distributed/tests/test_scheduler.py

@@ -1969,7 +1969,7 @@ async def test_scheduler_file():
 @pytest.mark.parametrize(
     "dashboard_address,expect",
     [
-        (None, ("::", "0.0.0.0")),
+        (None, ("::", "0.0.0.0", "127.0.0.1")),
         ("127.0.0.1:0", ("127.0.0.1",)),
     ],
 )

distributed/tests/test_worker.py

@@ -1115,7 +1115,7 @@ async def test_service_hosts_match_worker(s):
 
     async with Worker(s.address, host="tcp://127.0.0.1") as w:
         sock = first(w.http_server._sockets.values())
-        assert sock.getsockname()[0] in ("::", "0.0.0.0")
+        assert sock.getsockname()[0] in ("::", "127.0.0.1")
 
     # See what happens with e.g. `dask worker --listen-address tcp://:8811`
     async with Worker(s.address, host="") as w: