Refactor the devserver to make it easier to control caching

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

 # Copyright (c) 2012 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 object_store
 import operator
 
+from object_store_creator import ObjectStoreCreator
+
 class BranchUtility(object):
-  def __init__(self, base_path, fetcher, object_store):
-    self._base_path = base_path
+  def __init__(self, fetch_url, fetcher, object_store=None):
+    self._fetch_url = fetch_url
     self._fetcher = fetcher
+    if object_store is None:
+      object_store = ObjectStoreCreator(BranchUtility).Create()
     self._object_store = object_store
 
   @staticmethod
   def GetAllBranchNames():
     return ['stable', 'beta', 'dev', 'trunk']
 
   def GetAllBranchNumbers(self):
     return [(branch, self.GetBranchNumberForChannelName(branch))
             for branch in BranchUtility.GetAllBranchNames()]
 
-  def SplitChannelNameFromPath(self, path):
+  @staticmethod
+  def SplitChannelNameFromPath(path):
     """Splits the channel name out of |path|, returning the tuple
     (channel_name, real_path). If the channel cannot be determined then returns
     (None, path).
     """
     if '/' in path:
       first, second = path.split('/', 1)
     else:
       first, second = (path, '')
     if first in ['trunk', 'dev', 'beta', 'stable']:
       return (first, second)
     return (None, path)
 
   def GetBranchNumberForChannelName(self, channel_name):
     """Returns the branch number for a channel name.
     """
     if channel_name == 'trunk':
       return 'trunk'
 
-    branch_number = self._object_store.Get(channel_name + '.' + self._base_path,
-                                           object_store.BRANCH_UTILITY).Get()
+    branch_number = self._object_store.Get(channel_name).Get()
     if branch_number is not None:
       return branch_number
 
     try:
-      version_json = json.loads(self._fetcher.Fetch(self._base_path).content)
+      version_json = json.loads(self._fetcher.Fetch(self._fetch_url).content)
     except Exception as e:
       # This can happen if omahaproxy is misbehaving, which we've seen before.
       # Quick hack fix: just serve from trunk until it's fixed.
       logging.error('Failed to fetch or parse branch from omahaproxy: %s! '
                     'Falling back to "trunk".' % e)
       return 'trunk'
 
     branch_numbers = {}
     for entry in version_json:
       if entry['os'] not in ['win', 'linux', 'mac', 'cros']:
         continue
       for version in entry['versions']:
         if version['channel'] != channel_name:
           continue
         branch = version['version'].split('.')[2]
         if branch not in branch_numbers:
           branch_numbers[branch] = 0
         else:
           branch_numbers[branch] += 1
 
     sorted_branches = sorted(branch_numbers.iteritems(),
                              None,
                              operator.itemgetter(1),
                              True)
-    self._object_store.Set(channel_name + '.' + self._base_path,
-                           sorted_branches[0][0],
-                           object_store.BRANCH_UTILITY)
+    self._object_store.Set(channel_name, sorted_branches[0][0])
 
     return sorted_branches[0][0]