#!/usr/bin/env python # Copyright 2018 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. """Returns a timestamp that approximates the build date. build_type impacts the timestamp generated, both relative to the date of the last recent commit: - default: the build date is set to the most recent first Sunday of a month at 5:00am. The reason is that it is a time where invalidating the build cache shouldn't have major repercussions (due to lower load). - official: the build date is set to the time of the most recent commit. Either way, it is guaranteed to be in the past and always in UTC. """ # The requirements for the timestamp: # (1) for the purposes of continuous integration, longer duration # between cache invalidation is better, but >=1mo is preferable. # (2) for security purposes, timebombs would ideally be as close to # the actual time of the build as possible. It must be in the past. # (3) HSTS certificate pinning is valid for 70 days. To make CI builds enforce # HTST pinning, <=1mo is preferable. # # On Windows, the timestamp is also written in the PE/COFF file header of # executables of dlls. That timestamp and the executable's file size are # the only two pieces of information that identify a given executable on # the symbol server, so rarely changing timestamps can cause conflicts there # as well. We only upload symbols for official builds to the symbol server. from __future__ import print_function import argparse import calendar import datetime import doctest import os import sys THIS_DIR = os.path.abspath(os.path.dirname(__file__)) def GetFirstSundayOfMonth(year, month): """Returns the first sunday of the given month of the given year. >>> GetFirstSundayOfMonth(2016, 2) 7 >>> GetFirstSundayOfMonth(2016, 3) 6 >>> GetFirstSundayOfMonth(2000, 1) 2 """ weeks = calendar.Calendar().monthdays2calendar(year, month) # Return the first day in the first week that is a Sunday. return [date_day[0] for date_day in weeks[0] if date_day[1] == 6][0] def GetUnofficialBuildDate(build_date): """Gets the approximate build date given the specific build type. >>> GetUnofficialBuildDate(datetime.datetime(2016, 2, 6, 1, 2, 3)) datetime.datetime(2016, 1, 3, 5, 0) >>> GetUnofficialBuildDate(datetime.datetime(2016, 2, 7, 5)) datetime.datetime(2016, 2, 7, 5, 0) >>> GetUnofficialBuildDate(datetime.datetime(2016, 2, 8, 5)) datetime.datetime(2016, 2, 7, 5, 0) """ if build_date.hour < 5: # The time is locked at 5:00 am in UTC to cause the build cache # invalidation to not happen exactly at midnight. Use the same calculation # as the day before. # See //base/build_time.cc. build_date = build_date - datetime.timedelta(days=1) build_date = datetime.datetime(build_date.year, build_date.month, build_date.day, 5, 0, 0) day = build_date.day month = build_date.month year = build_date.year first_sunday = GetFirstSundayOfMonth(year, month) # If our build is after the first Sunday, we've already refreshed our build # cache on a quiet day, so just use that day. # Otherwise, take the first Sunday of the previous month. if day >= first_sunday: day = first_sunday else: month -= 1 if month == 0: month = 12 year -= 1 day = GetFirstSundayOfMonth(year, month) return datetime.datetime( year, month, day, build_date.hour, build_date.minute, build_date.second) def main(): if doctest.testmod()[0]: return 1 argument_parser = argparse.ArgumentParser() argument_parser.add_argument( 'build_type', help='The type of build', choices=('official', 'default')) args = argument_parser.parse_args() # The mtime of the revision in build/util/LASTCHANGE is stored in a file # next to it. Read it, to get a deterministic time close to "now". # That date is then modified as described at the top of the file so that # it changes less frequently than with every commit. # This intentionally always uses build/util/LASTCHANGE's commit time even if # use_dummy_lastchange is set. lastchange_file = os.path.join(THIS_DIR, 'util', 'LASTCHANGE.committime') last_commit_timestamp = int(open(lastchange_file).read()) build_date = datetime.datetime.utcfromtimestamp(last_commit_timestamp) # For official builds we want full fidelity time stamps because official # builds are typically added to symbol servers and Windows symbol servers # use the link timestamp as the prime differentiator, but for unofficial # builds we do lots of quantization to avoid churn. if args.build_type != 'official': build_date = GetUnofficialBuildDate(build_date) print(int(calendar.timegm(build_date.utctimetuple()))) return 0 if __name__ == '__main__': sys.exit(main())