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# 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
|
