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#!/usr/bin/env python3
# Copyright 2018 The Chromium Authors
# 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.
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.fromtimestamp(last_commit_timestamp,
datetime.timezone.utc)
# 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.
offset = 0
if args.build_type == 'official':
if os.name == 'nt':
version_path = os.path.join(THIS_DIR, os.pardir, 'chrome', 'VERSION')
with open(version_path) as f:
patch_line = f.readlines()[3].strip()
# Use the patch number as an offset to the build date so that multiple
# versions with different patch numbers built from the same source code
# will get different build_date values. This is critical for Windows
# symbol servers, to avoid collisions.
assert patch_line.startswith('PATCH=')
offset = int(patch_line[6:])
else:
build_date = GetUnofficialBuildDate(build_date)
print(offset + int(calendar.timegm(build_date.utctimetuple())))
return 0
if __name__ == '__main__':
sys.exit(main())
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