Docserver: Add @Cache annotation to CompiledFileSystem

This is the first in a series of CLs intended to reduce the amount of caching
in docserver code. The @Cache annotation is used to indicate that compiled data
should be cached in CompiledFileSystem.

NOTRY=True

Review URL: https://codereview.chromium.org/521693003

Cr-Commit-Position: refs/heads/master@{#292994}

6 files changed, 57 insertions, 25 deletions

diff --git a/chrome/common/extensions/docs/server2/api_models.py b/chrome/common/extensions/docs/server2/api_models.py
index 21d9329..69220ce 100644
--- a/chrome/common/extensions/docs/server2/api_models.py
+++ b/chrome/common/extensions/docs/server2/api_models.py
@@ -4,7 +4,7 @@
 
 import posixpath
 
-from compiled_file_system import SingleFile, Unicode
+from compiled_file_system import Cache, SingleFile, Unicode
 from extensions_paths import API_PATHS
 from features_bundle import HasParent, GetParentName
 from file_system import FileNotFoundError
@@ -64,6 +64,7 @@ class APIModels(object):
         file_system, self._CreateAPIModel, APIModels, category=self._platform)
     self._object_store = object_store_creator.Create(APIModels)
 
+  @Cache
   @SingleFile
   @Unicode
   def _CreateAPIModel(self, path, data):
diff --git a/chrome/common/extensions/docs/server2/compiled_file_system.py b/chrome/common/extensions/docs/server2/compiled_file_system.py
index 265391d..4729ccf 100644
--- a/chrome/common/extensions/docs/server2/compiled_file_system.py
+++ b/chrome/common/extensions/docs/server2/compiled_file_system.py
@@ -4,7 +4,6 @@
 
 import sys
 
-import schema_util
 from docs_server_utils import ToUnicode
 from file_system import FileNotFoundError
 from future import Future
@@ -14,9 +13,30 @@ from third_party.json_schema_compiler.memoize import memoize
 from third_party.motemplate import Motemplate
 
 
+_CACHEABLE_FUNCTIONS = set()
 _SINGLE_FILE_FUNCTIONS = set()
 
 
+def _GetUnboundFunction(fn):
+  '''Functions bound to an object are separate from the unbound
+  defintion. This causes issues when checking for cache membership,
+  so always get the unbound function, if possible.
+  '''
+  return getattr(fn, 'im_func', fn)
+
+
+def Cache(fn):
+  '''A decorator which can be applied to the compilation function
+  passed to CompiledFileSystem.Create, indicating that file/list data
+  should be cached.
+
+  This decorator should be listed first in any list of decorators, along
+  with the SingleFile decorator below.
+  '''
+  _CACHEABLE_FUNCTIONS.add(_GetUnboundFunction(fn))
+  return fn
+
+
 def SingleFile(fn):
   '''A decorator which can be optionally applied to the compilation function
   passed to CompiledFileSystem.Create, indicating that the function only
@@ -26,7 +46,7 @@ def SingleFile(fn):
   Note that this decorator must be listed first in any list of decorators to
   have any effect.
   '''
-  _SINGLE_FILE_FUNCTIONS.add(fn)
+  _SINGLE_FILE_FUNCTIONS.add(_GetUnboundFunction(fn))
   return fn
 
 
@@ -50,7 +70,7 @@ def Unicode(fn):
 class _CacheEntry(object):
   def __init__(self, cache_data, version):
 
-    self._cache_data = cache_data
+    self.cache_data = cache_data
     self.version = version
 
 
@@ -100,8 +120,8 @@ class CompiledFileSystem(object):
       These are memoized over file systems tied to different branches.
       '''
       return self.Create(file_system,
-                         SingleFile(lambda _, data:
-                             json_parse.Parse(ToUnicode(data))),
+                         Cache(SingleFile(lambda _, data:
+                             json_parse.Parse(ToUnicode(data)))),
                          CompiledFileSystem,
                          category='json')
 
@@ -134,6 +154,15 @@ class CompiledFileSystem(object):
     self._file_object_store = file_object_store
     self._list_object_store = list_object_store
 
+  def _Get(self, store, key):
+    if _GetUnboundFunction(self._compilation_function) in _CACHEABLE_FUNCTIONS:
+      return store.Get(key)
+    return Future(value=None)
+
+  def _Set(self, store, key, value):
+    if _GetUnboundFunction(self._compilation_function) in _CACHEABLE_FUNCTIONS:
+      store.Set(key, value)
+
   def _RecursiveList(self, path):
     '''Returns a Future containing the recursive directory listing of |path| as
     a flat list of paths.
@@ -179,7 +208,7 @@ class CompiledFileSystem(object):
         files += add_prefix(dir_name[len(path):], new_files)
       if dirs:
         files += self._file_system.Read(dirs).Then(
-            lambda results: get_from_future_listing(results)).Get()
+            get_from_future_listing).Get()
       return files
 
     return self._file_system.Read(add_prefix(path, first_layer_dirs)).Then(
@@ -199,13 +228,13 @@ class CompiledFileSystem(object):
       else:
         return Future(exc_info=sys.exc_info())
 
-    cache_entry = self._file_object_store.Get(path).Get()
+    cache_entry = self._Get(self._file_object_store, path).Get()
     if (cache_entry is not None) and (version == cache_entry.version):
-      return Future(value=cache_entry._cache_data)
+      return Future(value=cache_entry.cache_data)
 
     def compile_(files):
       cache_data = self._compilation_function(path, files)
-      self._file_object_store.Set(path, _CacheEntry(cache_data, version))
+      self._Set(self._file_object_store, path, _CacheEntry(cache_data, version))
       return cache_data
 
     return self._file_system.ReadSingle(
@@ -222,15 +251,15 @@ class CompiledFileSystem(object):
     except FileNotFoundError:
       return Future(exc_info=sys.exc_info())
 
-    cache_entry = self._list_object_store.Get(path).Get()
+    cache_entry = self._Get(self._list_object_store, path).Get()
     if (cache_entry is not None) and (version == cache_entry.version):
-      return Future(value=cache_entry._cache_data)
+      return Future(value=cache_entry.cache_data)
 
-    def next(files):
+    def compile_(files):
       cache_data = self._compilation_function(path, files)
-      self._list_object_store.Set(path, _CacheEntry(cache_data, version))
+      self._Set(self._list_object_store, path, _CacheEntry(cache_data, version))
       return cache_data
-    return self._RecursiveList(path).Then(next)
+    return self._RecursiveList(path).Then(compile_)
 
   # _GetFileVersionFromCache and _GetFileListingVersionFromCache are exposed
   # *only* so that ChainedCompiledFileSystem can optimise its caches. *Do not*
@@ -238,7 +267,7 @@ class CompiledFileSystem(object):
   # FileSystem.Stat on the FileSystem that this CompiledFileSystem uses.
 
   def _GetFileVersionFromCache(self, path):
-    cache_entry = self._file_object_store.Get(path).Get()
+    cache_entry = self._Get(self._file_object_store, path).Get()
     if cache_entry is not None:
       return Future(value=cache_entry.version)
     stat_future = self._file_system.StatAsync(path)
@@ -246,7 +275,7 @@ class CompiledFileSystem(object):
 
   def _GetFileListingVersionFromCache(self, path):
     path = ToDirectory(path)
-    cache_entry = self._list_object_store.Get(path).Get()
+    cache_entry = self._Get(self._list_object_store, path).Get()
     if cache_entry is not None:
       return Future(value=cache_entry.version)
     stat_future = self._file_system.StatAsync(path)
diff --git a/chrome/common/extensions/docs/server2/compiled_file_system_test.py b/chrome/common/extensions/docs/server2/compiled_file_system_test.py
index e1b930f..6564a43 100755
--- a/chrome/common/extensions/docs/server2/compiled_file_system_test.py
+++ b/chrome/common/extensions/docs/server2/compiled_file_system_test.py
@@ -6,7 +6,7 @@
 import functools
 import os
 
-from compiled_file_system import CompiledFileSystem
+from compiled_file_system import Cache, CompiledFileSystem
 from copy import deepcopy
 from environment import GetAppVersion
 from file_system import FileNotFoundError
@@ -87,7 +87,7 @@ class CompiledFileSystemTest(unittest.TestCase):
                      compiled_fs.GetFromFile('apps/fakedir/file.html').Get())
 
   def testPopulateFromFileListing(self):
-    def strip_ext(path, files):
+    def strip_ext(_, files):
       return [os.path.splitext(f)[0] for f in files]
     compiled_fs = _GetTestCompiledFsCreator()(strip_ext, CompiledFileSystemTest)
     expected_top_listing = [
@@ -121,7 +121,8 @@ class CompiledFileSystemTest(unittest.TestCase):
                          'apps/deepdir/deeper/').Get())
 
   def testCaching(self):
-    compiled_fs = _GetTestCompiledFsCreator()(identity, CompiledFileSystemTest)
+    compiled_fs = _GetTestCompiledFsCreator()(Cache(identity),
+                                              CompiledFileSystemTest)
     self.assertEqual('404.html contents',
                      compiled_fs.GetFromFile('404.html').Get())
     self.assertEqual(set(('file.html',)),
@@ -204,7 +205,7 @@ class CompiledFileSystemTest(unittest.TestCase):
     mock_fs = MockFileSystem(TestFileSystem(_TEST_DATA))
     compiled_fs = CompiledFileSystem.Factory(
         ObjectStoreCreator.ForTest()).Create(
-            mock_fs, lambda path, contents: contents, type(self))
+            mock_fs, Cache(lambda path, contents: contents), type(self))
 
     future = compiled_fs.GetFromFile('no_file', skip_not_found=True)
     # If the file doesn't exist, then the file system is not read.
diff --git a/chrome/common/extensions/docs/server2/redirector_test.py b/chrome/common/extensions/docs/server2/redirector_test.py
index 975c7be..caa4645 100755
--- a/chrome/common/extensions/docs/server2/redirector_test.py
+++ b/chrome/common/extensions/docs/server2/redirector_test.py
@@ -202,7 +202,7 @@ class RedirectorTest(unittest.TestCase):
           # the cron run. Returns strings parsed as JSON.
           # TODO(jshumway): Make a non hack version of this check.
           self._redirector._cache._file_object_store.Get(
-              path).Get()._cache_data)
+              path).Get().cache_data)
 
   def testDirectoryRedirection(self):
     # Simple redirect.
diff --git a/chrome/common/extensions/docs/server2/sidenav_data_source.py b/chrome/common/extensions/docs/server2/sidenav_data_source.py
index 1a7bae9..8521a45 100644
--- a/chrome/common/extensions/docs/server2/sidenav_data_source.py
+++ b/chrome/common/extensions/docs/server2/sidenav_data_source.py
@@ -6,7 +6,7 @@ import copy
 import logging
 import posixpath
 
-from compiled_file_system import SingleFile, Unicode
+from compiled_file_system import Cache, SingleFile, Unicode
 from data_source import DataSource
 from extensions_paths import JSON_TEMPLATES
 from future import Future
@@ -65,6 +65,7 @@ class SidenavDataSource(DataSource):
     self._server_instance = server_instance
     self._request = request
 
+  @Cache
   @SingleFile
   @Unicode
   def _CreateSidenavDict(self, _, content):
diff --git a/chrome/common/extensions/docs/server2/sidenav_data_source_test.py b/chrome/common/extensions/docs/server2/sidenav_data_source_test.py
index 4422acd..fc1b31a 100755
--- a/chrome/common/extensions/docs/server2/sidenav_data_source_test.py
+++ b/chrome/common/extensions/docs/server2/sidenav_data_source_test.py
@@ -149,11 +149,11 @@ class SamplesDataSourceTest(unittest.TestCase):
         ServerInstance.ForTest(file_system), request=None)
     sidenav_data_source.Cron().Get()
 
-    # If Cron fails, chrome_sidenav.json will not be cached, and the _cache_data
+    # If Cron fails, chrome_sidenav.json will not be cached, and the cache_data
     # access will fail.
     # TODO(jshumway): Make a non hack version of this check.
     sidenav_data_source._cache._file_object_store.Get(
-        '%schrome_sidenav.json' % JSON_TEMPLATES).Get()._cache_data
+        '%schrome_sidenav.json' % JSON_TEMPLATES).Get().cache_data
 
 
 if __name__ == '__main__':