Socket binding implemented properly for IPv6 and UNIX sockets. (#1641)

* Socket binding implemented properly for IPv6 and UNIX sockets.

- app.run("::1") for IPv6
- app.run("unix:/tmp/server.sock") for UNIX sockets
- app.run("localhost") retains old functionality (randomly either IPv4 or IPv6)

Do note that IPv6 and UNIX sockets are not fully supported by other Sanic facilities.
In particular, request.server_name and request.server_port are currently unreliable.

* Fix Windows compatibility by not referring to socket.AF_UNIX unless needed.

* Compatibility fix.

* Fix test of existing unix socket.

* Cleaner unix socket removal.

* Remove unix socket on exit also with workers=1.

* More pedantic UNIX socket implementation.

* Refactor app to take unix= argument instead of unix:-prefixed host. Goin' fast @ unix-socket fixed.

* Linter

* Proxy properties cleanup. Slight changes of semantics. SERVER_NAME now overrides everything.

* Have server fill in connection info instead of request asking the socket.

- Would be a good idea to remove request.transport entirely but I didn't dare to touch it yet.

* Linter 💣🌟✊💀

* Fix typing issues. request.server_name returns empty string if host header is missing.

* Fix tests

* Tests were failing, fix connection info.

* Linter nazi says you need that empty line.

* Rename a to addr, leave client empty for unix sockets.

* Add --unix support when sanic is run as module.

* Remove remove_route, deprecated in 19.6.

* Improved unix socket binding.

* More robust creating and unlinking of sockets. Show proper and not temporary name in conn_info.

* Add comprehensive tests for unix socket mode.

* Hide some imports inside functions to avoid Windows failure.

* Mention unix socket mode in deployment docs.

* Fix merge commit.

* Make test_unix_connection_multiple_workers pickleable for spawn mode multiprocessing.

Co-authored-by: L. Kärkkäinen <tronic@users.noreply.github.com>
Co-authored-by: Adam Hopkins <admhpkns@gmail.com>

sanic/app.py

@@ -1033,6 +1033,7 @@ class Sanic:
         stop_event: Any = None,
         register_sys_signals: bool = True,
         access_log: Optional[bool] = None,
+        unix: Optional[str] = None,
         loop: None = None,
     ) -> None:
         """Run the HTTP Server and listen until keyboard interrupt or term
@@ -1066,6 +1067,8 @@ class Sanic:
         :type register_sys_signals: bool
         :param access_log: Enables writing access logs (slows server)
         :type access_log: bool
+        :param unix: Unix socket to listen on instead of TCP port
+        :type unix: str
         :return: Nothing
         """
         if loop is not None:
@@ -1104,6 +1107,7 @@ class Sanic:
             debug=debug,
             ssl=ssl,
             sock=sock,
+            unix=unix,
             workers=workers,
             protocol=protocol,
             backlog=backlog,
@@ -1151,6 +1155,7 @@ class Sanic:
         backlog: int = 100,
         stop_event: Any = None,
         access_log: Optional[bool] = None,
+        unix: Optional[str] = None,
         return_asyncio_server=False,
         asyncio_server_kwargs=None,
     ) -> Optional[AsyncioServer]:
@@ -1220,6 +1225,7 @@ class Sanic:
             debug=debug,
             ssl=ssl,
             sock=sock,
+            unix=unix,
             loop=get_event_loop(),
             protocol=protocol,
             backlog=backlog,
@@ -1285,6 +1291,7 @@ class Sanic:
         debug=False,
         ssl=None,
         sock=None,
+        unix=None,
         workers=1,
         loop=None,
         protocol=HttpProtocol,
@@ -1326,6 +1333,7 @@ class Sanic:
             "host": host,
             "port": port,
             "sock": sock,
+            "unix": unix,
             "ssl": ssl,
             "app": self,
             "signal": Signal(),
@@ -1372,7 +1380,10 @@ class Sanic:
             proto = "http"
             if ssl is not None:
                 proto = "https"
-            logger.info(f"Goin' Fast @ {proto}://{host}:{port}")
+            if unix:
+                logger.info(f"Goin' Fast @ {unix} {proto}://...")
+            else:
+                logger.info(f"Goin' Fast @ {proto}://{host}:{port}")
 
         return server_settings