Docserver: Cache the samples.

chrome/common/extensions/docs/server2/samples_model.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import json
 import logging
 import posixpath
 import re
 
 from extensions_paths import EXAMPLES
@@ skipping 40 matching lines @@
     self._text_cache = compiled_fs_factory.ForUnicode(self._samples_fs)
     self._reference_resolver = reference_resolver
     self._base_path = base_path
     self._platform = platform
 
   def GetCache(self):
     return self._samples_cache
 
   def FilterSamples(self, api_name):
     '''Fetches and filters the list of samples for this platform, returning
-    only the samples that use the API |api_name|.
+    a Future to the only the samples that use the API |api_name|.
     '''
-    try:
+    def filter_samples(samples_list):
+      return [sample for sample in samples_list
+          if any(call['name'].startswith(api_name + '.')
+          for call in sample['api_calls'])]
+    def handle_error(_):
       # TODO(rockot): This cache is probably not working as intended, since
       # it can still lead to underlying filesystem (e.g. gitiles) access
       # while processing live requests. Because this can fail, we at least
       # trap and log exceptions to prevent 500s from being thrown.
-      samples_list = self._samples_cache.GetFromFileListing(
-          '' if self._platform == 'apps' else EXAMPLES).Get()
-    except Exception as e:
       logging.warning('Unable to get samples listing. Skipping.')
-      samples_list = []
-
-    return [sample for sample in samples_list if any(
-        call['name'].startswith(api_name + '.')
-        for call in sample['api_calls'])]
+      return []
+    platform_for_samples = '' if self._platform == 'apps' else EXAMPLES
+    return (self._samples_cache.GetFromFileListing(platform_for_samples)
+            .Then(filter_samples, error_handler=handle_error))
 
   def _GetDataFromManifest(self, path, file_system):
     manifest = self._text_cache.GetFromFile(path + '/manifest.json').Get()
     try:
       manifest_json = json.loads(json_comment_eater.Nom(manifest))
     except ValueError as e:
       logging.error('Error parsing manifest.json for %s: %s' % (path, e))
       return None
     l10n_data = {
       'name': manifest_json.get('name', ''),
@@ skipping 83 matching lines @@
       manifest_data.update({
         'icon': icon_path,
         'download_url': download_url,
         'url': url,
         'files': [f.replace(sample_path + '/', '') for f in sample_files],
         'api_calls': api_calls
       })
       samples_list.append(manifest_data)
 
     return samples_list