Refactor the devserver to make it easier to control caching

chrome/common/extensions/docs/server2/server_instance.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.
 
 from fnmatch import fnmatch
 import mimetypes
 import os
 
+from api_data_source import APIDataSource
+from api_list_data_source import APIListDataSource
+from appengine_blobstore import AppEngineBlobstore
+from appengine_url_fetcher import AppEngineUrlFetcher
+from branch_utility import BranchUtility
+from compiled_file_system import CompiledFileSystem
+from example_zipper import ExampleZipper
 from file_system import FileNotFoundError
-import compiled_file_system as compiled_fs
-
-STATIC_DIR_PREFIX = 'docs'
-DOCS_PATH = 'docs'
+from github_file_system import GithubFileSystem
+from in_memory_object_store import InMemoryObjectStore
+from intro_data_source import IntroDataSource
+from local_file_system import LocalFileSystem
+from caching_file_system import CachingFileSystem
+from object_store_creator import ObjectStoreCreator
+from path_canonicalizer import PathCanonicalizer
+from reference_resolver import ReferenceResolver
+from samples_data_source import SamplesDataSource
+from sidenav_data_source import SidenavDataSource
+from subversion_file_system import SubversionFileSystem
+import svn_constants
+from template_data_source import TemplateDataSource
+from third_party.json_schema_compiler.model import UnixName
+import url_constants
 
 def _IsBinaryMimetype(mimetype):
   return any(mimetype.startswith(prefix)
              for prefix in ['audio', 'image', 'video'])
 
 class ServerInstance(object):
-  """This class is used to hold a data source and fetcher for an instance of a
-  server. Each new branch will get its own ServerInstance.
-  """
-  def __init__(self,
-               template_data_source_factory,
-               example_zipper,
-               cache_factory):
-    self._template_data_source_factory = template_data_source_factory
-    self._example_zipper = example_zipper
-    self._cache = cache_factory.Create(lambda _, x: x, compiled_fs.STATIC)
+  '''Per-instance per-branch state.
+  '''
+  _instances = {}
+
+  branch_utility = None
+  github_file_system = None
+
+  @staticmethod
+  def GetOrCreate(channel):
+    branch_utility = ServerInstance.branch_utility

[cduvall, 2013/04/08 07:09:24]

is it necessary to assign ServerInstance.branch_utility to a new var? Could you
just do:

if ServerInstance.branch_utility is None:
  ServerInstance.branch_utility = .

[not at google - send to devlin, 2013/04/08 12:21:21]

Done. For GithubFileSystem too.

+    if branch_utility is None:
+      branch_utility = BranchUtility(url_constants.OMAHA_PROXY_URL,
+                                     AppEngineUrlFetcher())
+      ServerInstance.branch_utility = branch_utility
+
+    branch = branch_utility.GetBranchNumberForChannelName(channel)
+
+    # Use the branch as the key to |_instances| since the branch data is
+    # predictable while the channel data (channels can swich branches) isn't.
+    instance = ServerInstance._instances.get(branch)
+    if instance is None:
+      instance = ServerInstance._CreateForProduction(channel, branch)
+      ServerInstance._instances[branch] = instance
+    return instance
+
+  @staticmethod
+  def _CreateForProduction(channel, branch):
+    if branch == 'trunk':
+      svn_url = '/'.join((url_constants.SVN_TRUNK_URL,
+                          'src',
+                          svn_constants.EXTENSIONS_PATH))
+    else:
+      svn_url = '/'.join((url_constants.SVN_BRANCH_URL,
+                          branch,
+                          'src',
+                          svn_constants.EXTENSIONS_PATH))
+
+    viewvc_url = svn_url.replace(url_constants.SVN_URL,
+                                 url_constants.VIEWVC_URL)
+
+    svn_file_system = CachingFileSystem(
+        SubversionFileSystem(AppEngineUrlFetcher(svn_url),
+                             AppEngineUrlFetcher(viewvc_url)))
+
+    github_file_system = ServerInstance.github_file_system
+    if github_file_system is None:
+      github_file_system = GithubFileSystem(
+          AppEngineUrlFetcher(url_constants.GITHUB_URL),
+          AppEngineBlobstore())
+      ServerInstance.github_file_system = github_file_system
+
+    return ServerInstance(channel, svn_file_system, github_file_system)
+
+  @staticmethod
+  def CreateForTest(file_system):
+    return ServerInstance('test', file_system, None)
+
+  def __init__(self, channel, svn_file_system, github_file_system):
+    self.svn_file_system = svn_file_system
+
+    self.github_file_system = github_file_system
+
+    self.compiled_fs_factory = CompiledFileSystem.Factory(svn_file_system)
+
+    self.api_list_data_source_factory = APIListDataSource.Factory(
+        self.compiled_fs_factory,
+        svn_constants.API_PATH,
+        svn_constants.PUBLIC_TEMPLATE_PATH)
+
+    self.api_data_source_factory = APIDataSource.Factory(
+        self.compiled_fs_factory,
+        svn_constants.API_PATH)
+
+    self.ref_resolver_factory = ReferenceResolver.Factory(
+        self.api_data_source_factory,
+        self.api_list_data_source_factory)
+
+    self.api_data_source_factory.SetReferenceResolverFactory(
+        self.ref_resolver_factory)
+
+    self.samples_data_source_factory = SamplesDataSource.Factory(
+        channel,
+        self.svn_file_system,
+        ServerInstance.github_file_system,
+        self.ref_resolver_factory,
+        svn_constants.EXAMPLES_PATH)
+
+    self.api_data_source_factory.SetSamplesDataSourceFactory(
+        self.samples_data_source_factory)
+
+    self.intro_data_source_factory = IntroDataSource.Factory(
+        self.compiled_fs_factory,
+        self.ref_resolver_factory,
+        [svn_constants.INTRO_PATH, svn_constants.ARTICLE_PATH])
+
+    self.sidenav_data_source_factory = SidenavDataSource.Factory(
+        self.compiled_fs_factory,
+        svn_constants.JSON_PATH)
+
+    self.template_data_source_factory = TemplateDataSource.Factory(
+        channel,
+        self.api_data_source_factory,
+        self.api_list_data_source_factory,
+        self.intro_data_source_factory,
+        self.samples_data_source_factory,
+        self.sidenav_data_source_factory,
+        self.compiled_fs_factory,
+        self.ref_resolver_factory,
+        svn_constants.PUBLIC_TEMPLATE_PATH,
+        svn_constants.PRIVATE_TEMPLATE_PATH)
+
+    self.example_zipper = ExampleZipper(
+        self.svn_file_system,
+        self.compiled_fs_factory,
+        svn_constants.DOCS_PATH)
+
+    self.path_canonicalizer = PathCanonicalizer(
+        channel,
+        self.compiled_fs_factory)
+
+    self.content_cache = self.compiled_fs_factory.GetOrCreateIdentity()
 
   def _FetchStaticResource(self, path, response):
     """Fetch a resource in the 'static' directory.
     """
     mimetype = mimetypes.guess_type(path)[0] or 'text/plain'
     try:
-      result = self._cache.GetFromFile(STATIC_DIR_PREFIX + '/' + path,
-                                       binary=_IsBinaryMimetype(mimetype))
+      result = self.content_cache.GetFromFile(
+          svn_constants.DOCS_PATH + '/' + path,
+          binary=_IsBinaryMimetype(mimetype))
     except FileNotFoundError:
       return None
     response.headers['content-type'] = mimetype
     return result
 
   def Get(self, path, request, response):
-    # TODO(cduvall): bundle up all the request-scoped data into a single object.
-    templates = self._template_data_source_factory.Create(request, path)
+    templates = self.template_data_source_factory.Create(request, path)
+
+    if path.rsplit('/', 1)[-1] in ('favicon.ico', 'robots.txt'):
+      response.set_status(404)
+      response.out.write(templates.Render('404'))
+      return
 
     content = None
     if fnmatch(path, 'extensions/examples/*.zip'):
       try:
-        content = self._example_zipper.Create(
+        content = self.example_zipper.Create(
             path[len('extensions/'):-len('.zip')])
         response.headers['content-type'] = 'application/zip'
       except FileNotFoundError:
         content = None
     elif path.startswith('extensions/examples/'):
       mimetype = mimetypes.guess_type(path)[0] or 'text/plain'
       try:
-        content = self._cache.GetFromFile(
-            '%s/%s' % (DOCS_PATH, path[len('extensions/'):]),
+        content = self.content_cache.GetFromFile(
+            '%s/%s' % (svn_constants.DOCS_PATH, path[len('extensions/'):]),
             binary=_IsBinaryMimetype(mimetype))
         response.headers['content-type'] = 'text/plain'
       except FileNotFoundError:
         content = None
     elif path.startswith('static/'):
       content = self._FetchStaticResource(path, response)
     elif path.endswith('.html'):
       content = templates.Render(path)
 
     response.headers['x-frame-options'] = 'sameorigin'
     if content:
       response.headers['cache-control'] = 'max-age=300'
       response.out.write(content)
     else:
       response.set_status(404);
       response.out.write(templates.Render('404'))