| # 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 |
| |
| _APP_YAML_CONTAINER = ''' |
| application: chrome-apps-doc |
| version: %s |
| runtime: python27 |
| api_version: 1 |
| threadsafe: false |
| ''' |
| |
| class AppYamlHelper(object): |
| '''Parses the app.yaml file, and is able to step back in the host file |
| system's revision history to find when it changed to some given version. |
| ''' |
| def __init__(self, |
| app_yaml_path, |
| file_system_at_head, |
| object_store_creator, |
| host_file_system_creator): |
| self._app_yaml_path = app_yaml_path |
| self._file_system_at_head = file_system_at_head |
| self._store = object_store_creator.Create( |
| AppYamlHelper, |
| category=file_system_at_head.GetIdentity(), |
| start_empty=False) |
| self._host_file_system_creator = host_file_system_creator |
| |
| @staticmethod |
| def ExtractVersion(app_yaml, key='version'): |
| '''Extracts the 'version' key from the contents of an app.yaml file. |
| Allow overriding the key to parse e.g. the cron file ('target'). |
| ''' |
| # We could properly parse this using a yaml library but Python doesn't have |
| # one built in so whatevs. |
| key_colon = '%s:' % key |
| versions = [line.strip()[len(key_colon):].strip() |
| for line in app_yaml.split('\n') |
| if line.strip().startswith(key_colon)] |
| if not versions: |
| raise ValueError('No versions found for %s in %s' % ( |
| key, app_yaml)) |
| if len(set(versions)) > 1: |
| raise ValueError('Inconsistent versions found for %s in %s: %s' % ( |
| key, app_yaml, versions)) |
| return versions[0] |
| |
| @staticmethod |
| def IsGreater(lhs, rhs): |
| '''Return whether the app.yaml version |lhs| > |rhs|. This is tricky |
| because versions are typically not numbers but rather 2-0-9, 2-0-12, |
| 2-1-0, etc - and 2-1-0 > 2-0-10 > 2-0-9. |
| ''' |
| lhs_parts = lhs.replace('-', '.').split('.') |
| rhs_parts = rhs.replace('-', '.').split('.') |
| while lhs_parts and rhs_parts: |
| lhs_msb = int(lhs_parts.pop(0)) |
| rhs_msb = int(rhs_parts.pop(0)) |
| if lhs_msb != rhs_msb: |
| return lhs_msb > rhs_msb |
| return len(lhs) > len(rhs) |
| |
| @staticmethod |
| def GenerateAppYaml(version): |
| '''Probably only useful for tests. |
| ''' |
| return _APP_YAML_CONTAINER % version |
| |
| def IsUpToDate(self, app_version): |
| '''Returns True if the |app_version| is up to date with respect to the one |
| checked into the host file system. |
| ''' |
| checked_in_app_version = AppYamlHelper.ExtractVersion( |
| self._file_system_at_head.ReadSingle(self._app_yaml_path)) |
| if app_version == checked_in_app_version: |
| return True |
| if AppYamlHelper.IsGreater(app_version, checked_in_app_version): |
| logging.warning( |
| 'Server is too new! Checked in %s < currently running %s' % ( |
| checked_in_app_version, app_version)) |
| return True |
| return False |
| |
| def GetFirstRevisionGreaterThan(self, app_version): |
| '''Finds the first revision that the version in app.yaml was greater than |
| |app_version|. |
| |
| WARNING: if there is no such revision (e.g. the app is up to date, or |
| *oops* the app is even newer) then this will throw a ValueError. Use |
| IsUpToDate to validate the input before calling this method. |
| ''' |
| stored = self._store.Get(app_version).Get() |
| if stored is None: |
| stored = self._GetFirstRevisionGreaterThanImpl(app_version) |
| assert stored is not None |
| self._store.Set(app_version, stored) |
| return stored |
| |
| def _GetFirstRevisionGreaterThanImpl(self, app_version): |
| def get_app_yaml_revision(file_system): |
| return int(file_system.Stat(self._app_yaml_path).version) |
| |
| def has_greater_app_version(file_system): |
| app_version_in_file_system = AppYamlHelper.ExtractVersion( |
| file_system.ReadSingle(self._app_yaml_path)) |
| return AppYamlHelper.IsGreater(app_version_in_file_system, app_version) |
| |
| found = None |
| next_file_system = self._file_system_at_head |
| |
| while has_greater_app_version(next_file_system): |
| found = get_app_yaml_revision(next_file_system) |
| # Back up a revision then find when app.yaml was last updated before then. |
| if found == 0: |
| logging.warning('All revisions are greater than %s' % app_version) |
| return 0 |
| next_file_system = self._host_file_system_creator.Create( |
| revision=found - 1) |
| |
| if found is None: |
| raise ValueError('All revisions are less than %s' % app_version) |
| return found |