Gateway only: Ensure launch and request timeouts are in sync (#5317)

Prior to this change, the request timeout for a Gateway request
was synchronized with KERNEL_LAUNCH_TIMEOUT only if KLT
was greater. However, the two are closely associated and KLT
should be adjusted if the configurable request_timeout is greater.
This change ensures that the two values are synchronized to the
greater value. It changes the two configurable timeouts to default
to 40 (to match that of KLT) and removes the 2-second pad,
since that wasn't helpful and only confused the situation.

These changes were prompted by this issue: jupyter-server/enterprise_gateway#792

jupyter_server/gateway/managers.py

@@ -102,7 +102,7 @@ def _kernelspecs_endpoint_default(self):
     def _kernelspecs_resource_endpoint_default(self):
         return os.environ.get(self.kernelspecs_resource_endpoint_env, self.kernelspecs_resource_endpoint_default_value)
 
-    connect_timeout_default_value = 60.0
+    connect_timeout_default_value = 40.0
     connect_timeout_env = 'JUPYTER_GATEWAY_CONNECT_TIMEOUT'
     connect_timeout = Float(default_value=connect_timeout_default_value, config=True,
         help="""The time allowed for HTTP connection establishment with the Gateway server.
@@ -112,7 +112,7 @@ def _kernelspecs_resource_endpoint_default(self):
     def connect_timeout_default(self):
         return float(os.environ.get('JUPYTER_GATEWAY_CONNECT_TIMEOUT', self.connect_timeout_default_value))
 
-    request_timeout_default_value = 60.0
+    request_timeout_default_value = 40.0
     request_timeout_env = 'JUPYTER_GATEWAY_REQUEST_TIMEOUT'
     request_timeout = Float(default_value=request_timeout_default_value, config=True,
         help="""The time allowed for HTTP request completion. (JUPYTER_GATEWAY_REQUEST_TIMEOUT env var)""")
@@ -226,18 +226,20 @@ def gateway_enabled(self):
 
     # Ensure KERNEL_LAUNCH_TIMEOUT has a default value.
     KERNEL_LAUNCH_TIMEOUT = int(os.environ.get('KERNEL_LAUNCH_TIMEOUT', 40))
-    os.environ['KERNEL_LAUNCH_TIMEOUT'] = str(KERNEL_LAUNCH_TIMEOUT)
-
-    LAUNCH_TIMEOUT_PAD = int(os.environ.get('LAUNCH_TIMEOUT_PAD', 2))
 
     def init_static_args(self):
         """Initialize arguments used on every request.  Since these are static values, we'll
         perform this operation once.
 
         """
-        # Ensure that request timeout is at least "pad" greater than launch timeout.
-        if self.request_timeout < float(GatewayClient.KERNEL_LAUNCH_TIMEOUT + GatewayClient.LAUNCH_TIMEOUT_PAD):
-            self.request_timeout = float(GatewayClient.KERNEL_LAUNCH_TIMEOUT + GatewayClient.LAUNCH_TIMEOUT_PAD)
+        # Ensure that request timeout and KERNEL_LAUNCH_TIMEOUT are the same, taking the
+        #  greater value of the two.
+        if self.request_timeout < float(GatewayClient.KERNEL_LAUNCH_TIMEOUT):
+            self.request_timeout = float(GatewayClient.KERNEL_LAUNCH_TIMEOUT)
+        elif self.request_timeout > float(GatewayClient.KERNEL_LAUNCH_TIMEOUT):
+            GatewayClient.KERNEL_LAUNCH_TIMEOUT = int(self.request_timeout)
+        # Ensure any adjustments are reflected in env.
+        os.environ['KERNEL_LAUNCH_TIMEOUT'] = str(GatewayClient.KERNEL_LAUNCH_TIMEOUT)
 
         self._static_args['headers'] = json.loads(self.headers)
         if 'Authorization' not in self._static_args['headers'].keys():

tests/test_gateway.py

@@ -152,24 +152,28 @@ async def test_gateway_env_options(init_gateway, jp_serverapp):
     assert jp_serverapp.gateway_config.connect_timeout == jp_serverapp.gateway_config.request_timeout
     assert jp_serverapp.gateway_config.connect_timeout == 44.4
 
+    GatewayClient.instance().init_static_args()
+    assert GatewayClient.instance().KERNEL_LAUNCH_TIMEOUT == int(jp_serverapp.gateway_config.request_timeout)
+
 
 async def test_gateway_cli_options(jp_configurable_serverapp):
     argv = [
         '--gateway-url=' + mock_gateway_url,
         '--GatewayClient.http_user=' + mock_http_user,
         '--GatewayClient.connect_timeout=44.4',
-        '--GatewayClient.request_timeout=44.4'
+        '--GatewayClient.request_timeout=96.0'
     ]
 
-
     GatewayClient.clear_instance()
     app = jp_configurable_serverapp(argv=argv)
 
     assert app.gateway_config.gateway_enabled is True
     assert app.gateway_config.url == mock_gateway_url
     assert app.gateway_config.http_user == mock_http_user
-    assert app.gateway_config.connect_timeout == app.gateway_config.request_timeout
     assert app.gateway_config.connect_timeout == 44.4
+    assert app.gateway_config.request_timeout == 96.0
+    GatewayClient.instance().init_static_args()
+    assert GatewayClient.instance().KERNEL_LAUNCH_TIMEOUT == 96  # Ensure KLT gets set from request-timeout
     GatewayClient.clear_instance()