Fix Can't connect to compute local on some computers

Chicken and egg problem we try to connect to compute
before http was available. I rewrote the code to prevent
erase of settings and rollback the beta4 code for init.

Fix #946

gns3server/controller/__init__.py

@@ -248,7 +248,6 @@ class Controller:
         """
         Store settings shared by the different GUI will be replace by dedicated API later. Dictionnary
         """
-        assert self._settings is not None
         return self._settings
 
     @settings.setter

gns3server/handlers/api/controller/server_handler.py

@@ -103,7 +103,15 @@ class ServerHandler:
         description="Retrieve gui settings from the server. Temporary will we removed in later release")
     def read_settings(request, response):
 
-        response.json(Controller.instance().settings)
+        settings = None
+        while True:
+            # The init of the server could take some times
+            # we ensure settings are loaded before returning them
+            settings = Controller.instance().settings
+            if settings is not None:
+                break
+            yield from asyncio.sleep(0.5)
+        response.json(settings)
 
     @Route.post(
         r"/settings",
@@ -113,6 +121,8 @@ class ServerHandler:
         })
     def write_settings(request, response):
         controller = Controller.instance()
+        if controller.settings is None:  # Server is not loaded ignore settings update to prevent buggy client sync issue
+            return
         controller.settings = request.json
         try:
             controller.save()

gns3server/web/web_server.py

@@ -186,6 +186,13 @@ class WebServer:
 
         atexit.register(close_asyncio_loop)
 
+    @asyncio.coroutine
+    def _on_startup(self, *args):
+        """
+        Called when the HTTP server start
+        """
+        yield from Controller.instance().start()
+
     def run(self):
         """
         Starts the server.
@@ -225,8 +232,9 @@ class WebServer:
         for key, val in os.environ.items():
             log.debug("ENV %s=%s", key, val)
 
-        self._loop.run_until_complete(Controller.instance().start())
         self._app = aiohttp.web.Application()
+        # Background task started with the server
+        self._app.on_startup.append(self._on_startup)
 
         # Allow CORS for this domains
         cors = aiohttp_cors.setup(self._app, defaults={