Docserver: refactor the Handler/ServerInstance relationship into a servlet

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

+# Copyright 2013 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 logging
+import time
+import traceback
+
+from appengine_wrappers import DeadlineExceededError, logservice
+from branch_utility import BranchUtility
+from render_servlet import RenderServlet
+from server_instance import ServerInstance
+from servlet import Servlet, Request, Response
+import svn_constants
+
+class CronServlet(Servlet):
+  '''Servlet which runs a cron job.
+  '''
+  def Get(self):
+    # Crons often time out, and when they do *and* then eventually try to
+    # flush logs they die. Turn off autoflush and manually do so at the end.
+    logservice.AUTOFLUSH_ENABLED = False
+    try:
+      return self._GetImpl()
+    finally:
+      logservice.flush()
+
+  def _GetImpl(self):
+    # Cron strategy:
+    #
+    # Find all public template files and static files, and render them. Most of
+    # the time these won't have changed since the last cron run, so it's a
+    # little wasteful, but hopefully rendering is really fast (if it isn't we
+    # have a problem).
+    channel = self._request.path.strip('/')
+    logging.info('cron/%s: starting' % channel)
+
+    server_instance = ServerInstance.CreateOnline(channel)
+
+    def run_cron_for_dir(d, path_prefix=''):
+      success = True
+      start_time = time.time()
+      files = [f for f in server_instance.content_cache.GetFromFileListing(d)
+               if not f.endswith('/')]
+      logging.info('cron/%s: rendering %s files from %s...' % (
+          channel, len(files), d))
+      try:
+        for i, f in enumerate(files):
+          error = None
+          path = '%s%s' % (path_prefix, f)
+          try:
+            response = RenderServlet(Request(path, self._request.headers)).Get(
+                server_instance=server_instance)
+            if response.status != 200:
+              error = 'Got %s response' % response.status
+          except DeadlineExceededError:
+            logging.error(
+                'cron/%s: deadline exceeded rendering %s (%s of %s): %s' % (
+                    channel, path, i + 1, len(files), traceback.format_exc()))
+            raise
+          except error:
+            pass
+          if error:
+            logging.error('cron/%s: error rendering %s: %s' % (
+                channel, path, error))
+            success = False
+      finally:
+        logging.info('cron/%s: rendering %s files from %s took %s seconds' % (
+            channel, len(files), d, time.time() - start_time))
+      return success
+
+    success = True
+    for path, path_prefix in (
+        # Note: rendering the public templates will pull in all of the private
+        # templates.
+        (svn_constants.PUBLIC_TEMPLATE_PATH, ''),
+        # Note: rendering the public templates will have pulled in the .js and
+        # manifest.json files (for listing examples on the API reference pages),
+        # but there are still images, CSS, etc.
+        (svn_constants.STATIC_PATH, 'static/'),
+        (svn_constants.EXAMPLES_PATH, 'extensions/examples/')):
+      try:
+        # Note: don't try to short circuit any of this stuff. We want to run
+        # the cron for all the directories regardless of intermediate failures.
+        success = run_cron_for_dir(path, path_prefix=path_prefix) and success
+      except DeadlineExceededError:
+        success = False
+        break
+
+    logging.info('cron/%s: finished' % channel)
+
+    return (Response.Ok('Success') if success else
+            Response.InternalError('Failure'))