Move environment variables to SingletonConfigurable

Created a singleton class `Gateway` to store all configuration options
for a Gateway.  This class also holds some help methods to make it easier
to use the options and determine if the gateway option is enabled.

Updated the NotebookTestBase class to allow for subclasses to infuence
the patched environment as well as command line options via argv.

Added a test to ensure various gateway configuration items can be
set via the environment or command-line.

notebook/gateway/handlers.py

@@ -21,27 +21,7 @@
 from jupyter_client.session import Session
 from traitlets.config.configurable import LoggingConfigurable
 
-# Note: Although some of these are available via NotebookApp (command line), we will
-# take the approach of using environment variables to enable separate sets of values
-# for use with the local Notebook server (via command-line) and remote Gateway server
-# (via environment variables).
-
-GATEWAY_HEADERS = json.loads(os.getenv('GATEWAY_HEADERS', '{}'))
-GATEWAY_HEADERS.update({
-    'Authorization': 'token {}'.format(os.getenv('GATEWAY_AUTH_TOKEN', ''))
-})
-VALIDATE_GATEWAY_CERT = os.getenv('VALIDATE_GATEWAY_CERT') not in ['no', 'false']
-
-GATEWAY_CLIENT_KEY = os.getenv('GATEWAY_CLIENT_KEY')
-GATEWAY_CLIENT_CERT = os.getenv('GATEWAY_CLIENT_CERT')
-GATEWAY_CLIENT_CA = os.getenv('GATEWAY_CLIENT_CA')
-
-GATEWAY_HTTP_USER = os.getenv('GATEWAY_HTTP_USER')
-GATEWAY_HTTP_PASS = os.getenv('GATEWAY_HTTP_PASS')
-
-# Get env variables to handle timeout of request and connection
-GATEWAY_CONNECT_TIMEOUT = float(os.getenv('GATEWAY_CONNECT_TIMEOUT', 20.0))
-GATEWAY_REQUEST_TIMEOUT = float(os.getenv('GATEWAY_REQUEST_TIMEOUT', 20.0))
+from .managers import Gateway
 
 
 class WebSocketChannelsHandler(WebSocketHandler, IPythonHandler):
@@ -77,7 +57,7 @@ def authenticate(self):
     def initialize(self):
         self.log.debug("Initializing websocket connection %s", self.request.path)
         self.session = Session(config=self.config)
-        self.gateway = GatewayWebSocketClient(gateway_url=self.kernel_manager.parent.gateway_url)
+        self.gateway = GatewayWebSocketClient(gateway_url=Gateway.instance().url)
 
     @gen.coroutine
     def get(self, kernel_id, *args, **kwargs):
@@ -135,7 +115,6 @@ class GatewayWebSocketClient(LoggingConfigurable):
 
     def __init__(self, **kwargs):
         super(GatewayWebSocketClient, self).__init__(**kwargs)
-        self.gateway_url = kwargs['gateway_url']
         self.kernel_id = None
         self.ws = None
         self.ws_future = Future()
@@ -145,29 +124,14 @@ def __init__(self, **kwargs):
     def _connect(self, kernel_id):
         self.kernel_id = kernel_id
         ws_url = url_path_join(
-            os.getenv('GATEWAY_WS_URL', self.gateway_url.replace('http', 'ws')),
-            '/api/kernels', 
-            url_escape(kernel_id),
-            'channels'
+            Gateway.instance().ws_url,
+            Gateway.instance().kernels_endpoint, url_escape(kernel_id), 'channels'
         )
         self.log.info('Connecting to {}'.format(ws_url))
-        parameters = {
-          "headers": GATEWAY_HEADERS,
-          "validate_cert": VALIDATE_GATEWAY_CERT,
-          "connect_timeout": GATEWAY_CONNECT_TIMEOUT,
-          "request_timeout": GATEWAY_REQUEST_TIMEOUT
-        }
-        if GATEWAY_HTTP_USER:
-            parameters["auth_username"] = GATEWAY_HTTP_USER
-        if GATEWAY_HTTP_PASS:
-            parameters["auth_password"] = GATEWAY_HTTP_PASS
-        if GATEWAY_CLIENT_KEY:
-            parameters["client_key"] = GATEWAY_CLIENT_KEY
-            parameters["client_cert"] = GATEWAY_CLIENT_CERT
-            if GATEWAY_CLIENT_CA:
-                parameters["ca_certs"] = GATEWAY_CLIENT_CA
-
-        request = HTTPRequest(ws_url, **parameters)
+        kwargs = {}
+        kwargs = Gateway.instance().load_connection_args(**kwargs)
+
+        request = HTTPRequest(ws_url, **kwargs)
         self.ws_future = websocket_connect(request)
         self.ws_future.add_done_callback(self._connection_done)
 
@@ -178,7 +142,7 @@ def _connection_done(self, fut):
         else:
             self.log.warning("Websocket connection has been cancelled via client disconnect before its establishment.  "
                              "Kernel with ID '{}' may not be terminated on Gateway: {}".
-                             format(self.kernel_id, self.gateway_url))
+                             format(self.kernel_id, Gateway.instance().url))
 
     def _disconnect(self):
         if self.ws is not None:
@@ -343,18 +307,15 @@ def get(self):
         # NOTE: We do this here since this handler is called during the Notebook's startup and subsequent refreshes
         # of the tree view.
         except ConnectionRefusedError:
-            gateway_url = ksm.parent.gateway_url
             self.log.error("Connection refused from Gateway server url '{}'.  "
-                         "Check to be sure the Gateway instance is running.".format(gateway_url))
+                         "Check to be sure the Gateway instance is running.".format(Gateway.instance().url))
         except HTTPTimeoutError:
             # This can occur if the host is valid (e.g., foo.com) but there's nothing there.
-            gateway_url = ksm.parent.gateway_url
             self.log.error("Timeout error attempting to connect to Gateway server url '{}'.  "
-                         "Ensure gateway_url is valid and the Gateway instance is running.".format(gateway_url))
+                         "Ensure gateway url is valid and the Gateway instance is running.".format(Gateway.instance().url))
         except gaierror as e:
-            gateway_url = ksm.parent.gateway_url
             self.log.error("The Gateway server specified in the gateway_url '{}' doesn't appear to be valid.  "
-                         "Ensure gateway_url is valid and the Gateway instance is running.".format(gateway_url))
+                         "Ensure gateway url is valid and the Gateway instance is running.".format(Gateway.instance().url))
 
         self.finish()