Find available kernelspecs more efficiently

Closes gh-3135

Author: takluyver

notebook/services/kernelspecs/handlers.py

@@ -16,17 +16,19 @@
 from ...base.handlers import APIHandler
 from ...utils import url_path_join, url_unescape
 
-def kernelspec_model(handler, name):
+def kernelspec_model(handler, name, spec_dict, resource_dir):
     """Load a KernelSpec by name and return the REST API model"""
-    ksm = handler.kernel_spec_manager
-    spec = ksm.get_kernel_spec(name)
-    d = {'name': name}
-    d['spec'] = spec.to_dict()
-    d['resources'] = resources = {}
-    resource_dir = spec.resource_dir
+    d = {
+        'name': name,
+        'spec': spec_dict,
+        'resources': {}
+    }
+
+    # Add resource files if they exist
+    resource_dir = resource_dir
     for resource in ['kernel.js', 'kernel.css']:
         if os.path.exists(pjoin(resource_dir, resource)):
-            resources[resource] = url_path_join(
+            d['resources'][resource] = url_path_join(
                 handler.base_url,
                 'kernelspecs',
                 name,
@@ -35,7 +37,7 @@ def kernelspec_model(handler, name):
     for logo_file in glob.glob(pjoin(resource_dir, 'logo-*')):
         fname = os.path.basename(logo_file)
         no_ext, _ = os.path.splitext(fname)
-        resources[no_ext] = url_path_join(
+        d['resources'][no_ext] = url_path_join(
             handler.base_url,
             'kernelspecs',
             name,
@@ -52,9 +54,10 @@ def get(self):
         model = {}
         model['default'] = km.default_kernel_name
         model['kernelspecs'] = specs = {}
-        for kernel_name in ksm.find_kernel_specs():
+        for kernel_name, kernel_info in ksm.get_all_specs().items():
             try:
-                d = kernelspec_model(self, kernel_name)
+                d = kernelspec_model(self, kernel_name, kernel_info['spec'],
+                                     kernel_info['resource_dir'])
             except Exception:
                 self.log.error("Failed to load kernel spec: '%s'", kernel_name, exc_info=True)
                 continue
@@ -67,10 +70,13 @@ class KernelSpecHandler(APIHandler):
 
     @web.authenticated
     def get(self, kernel_name):
+        ksm = self.kernel_spec_manager
+        kernel_name = url_unescape(kernel_name)
         try:
-            model = kernelspec_model(self, url_unescape(kernel_name))
+            spec = ksm.get_kernel_spec(kernel_name)
         except KeyError:
             raise web.HTTPError(404, u'Kernel spec %s not found' % kernel_name)
+        model = kernelspec_model(self, kernel_name, spec.to_dict(), spec.resource_dir)
         self.set_header("Content-Type", 'application/json')
         self.finish(json.dumps(model))
 

setup.py

@@ -148,7 +148,7 @@
     'ipython_genutils',
     'traitlets>=4.2.1',
     'jupyter_core>=4.4.0',
-    'jupyter_client',
+    'jupyter_client>=4.2.0',
     'nbformat',
     'nbconvert',
     'ipykernel', # bless IPython kernel for now