compute_build_timestamp.py (5467B)
1 #!/usr/bin/env python3 2 # Copyright 2018 The Chromium Authors 3 # Use of this source code is governed by a BSD-style license that can be 4 # found in the LICENSE file. 5 """Returns a timestamp that approximates the build date. 6 7 build_type impacts the timestamp generated, both relative to the date of the 8 last recent commit: 9 - default: the build date is set to the most recent first Sunday of a month at 10 5:00am. The reason is that it is a time where invalidating the build cache 11 shouldn't have major repercussions (due to lower load). 12 - official: the build date is set to the time of the most recent commit. 13 Either way, it is guaranteed to be in the past and always in UTC. 14 """ 15 16 # The requirements for the timestamp: 17 # (1) for the purposes of continuous integration, longer duration 18 # between cache invalidation is better, but >=1mo is preferable. 19 # (2) for security purposes, timebombs would ideally be as close to 20 # the actual time of the build as possible. It must be in the past. 21 # (3) HSTS certificate pinning is valid for 70 days. To make CI builds enforce 22 # HTST pinning, <=1mo is preferable. 23 # 24 # On Windows, the timestamp is also written in the PE/COFF file header of 25 # executables of dlls. That timestamp and the executable's file size are 26 # the only two pieces of information that identify a given executable on 27 # the symbol server, so rarely changing timestamps can cause conflicts there 28 # as well. We only upload symbols for official builds to the symbol server. 29 30 31 import argparse 32 import calendar 33 import datetime 34 import doctest 35 import os 36 import sys 37 38 39 THIS_DIR = os.path.abspath(os.path.dirname(__file__)) 40 41 42 def GetFirstSundayOfMonth(year, month): 43 """Returns the first sunday of the given month of the given year. 44 45 >>> GetFirstSundayOfMonth(2016, 2) 46 7 47 >>> GetFirstSundayOfMonth(2016, 3) 48 6 49 >>> GetFirstSundayOfMonth(2000, 1) 50 2 51 """ 52 weeks = calendar.Calendar().monthdays2calendar(year, month) 53 # Return the first day in the first week that is a Sunday. 54 return [date_day[0] for date_day in weeks[0] if date_day[1] == 6][0] 55 56 57 def GetUnofficialBuildDate(build_date): 58 """Gets the approximate build date given the specific build type. 59 60 >>> GetUnofficialBuildDate(datetime.datetime(2016, 2, 6, 1, 2, 3)) 61 datetime.datetime(2016, 1, 3, 5, 0) 62 >>> GetUnofficialBuildDate(datetime.datetime(2016, 2, 7, 5)) 63 datetime.datetime(2016, 2, 7, 5, 0) 64 >>> GetUnofficialBuildDate(datetime.datetime(2016, 2, 8, 5)) 65 datetime.datetime(2016, 2, 7, 5, 0) 66 """ 67 68 if build_date.hour < 5: 69 # The time is locked at 5:00 am in UTC to cause the build cache 70 # invalidation to not happen exactly at midnight. Use the same calculation 71 # as the day before. 72 # See //base/build_time.cc. 73 build_date = build_date - datetime.timedelta(days=1) 74 build_date = datetime.datetime(build_date.year, build_date.month, 75 build_date.day, 5, 0, 0) 76 77 day = build_date.day 78 month = build_date.month 79 year = build_date.year 80 first_sunday = GetFirstSundayOfMonth(year, month) 81 # If our build is after the first Sunday, we've already refreshed our build 82 # cache on a quiet day, so just use that day. 83 # Otherwise, take the first Sunday of the previous month. 84 if day >= first_sunday: 85 day = first_sunday 86 else: 87 month -= 1 88 if month == 0: 89 month = 12 90 year -= 1 91 day = GetFirstSundayOfMonth(year, month) 92 return datetime.datetime( 93 year, month, day, build_date.hour, build_date.minute, build_date.second) 94 95 96 def main(): 97 if doctest.testmod()[0]: 98 return 1 99 argument_parser = argparse.ArgumentParser() 100 argument_parser.add_argument( 101 'build_type', help='The type of build', choices=('official', 'default')) 102 args = argument_parser.parse_args() 103 104 # The mtime of the revision in build/util/LASTCHANGE is stored in a file 105 # next to it. Read it, to get a deterministic time close to "now". 106 # That date is then modified as described at the top of the file so that 107 # it changes less frequently than with every commit. 108 # This intentionally always uses build/util/LASTCHANGE's commit time even if 109 # use_dummy_lastchange is set. 110 lastchange_file = os.path.join(THIS_DIR, 'util', 'LASTCHANGE.committime') 111 last_commit_timestamp = int(open(lastchange_file).read()) 112 build_date = datetime.datetime.fromtimestamp(last_commit_timestamp, 113 datetime.timezone.utc) 114 115 # For official builds we want full fidelity time stamps because official 116 # builds are typically added to symbol servers and Windows symbol servers 117 # use the link timestamp as the prime differentiator, but for unofficial 118 # builds we do lots of quantization to avoid churn. 119 offset = 0 120 if args.build_type == 'official': 121 if os.name == 'nt': 122 version_path = os.path.join(THIS_DIR, os.pardir, 'chrome', 'VERSION') 123 with open(version_path) as f: 124 patch_line = f.readlines()[3].strip() 125 # Use the patch number as an offset to the build date so that multiple 126 # versions with different patch numbers built from the same source code 127 # will get different build_date values. This is critical for Windows 128 # symbol servers, to avoid collisions. 129 assert patch_line.startswith('PATCH=') 130 offset = int(patch_line[6:]) 131 else: 132 build_date = GetUnofficialBuildDate(build_date) 133 print(offset + int(calendar.timegm(build_date.utctimetuple()))) 134 return 0 135 136 137 if __name__ == '__main__': 138 sys.exit(main())