Slightly Less Painful Time Zones (RailsConf)

Abstract:
For developers, there are two things that are certain for time zones: you can’t avoid having to deal with them, and you will screw them up at some point. There are, however, some ways to mitigate the pain. This talk will discuss tactics for avoiding time zone mayhem, using a feature to send out weekly email reports in a customer’s local time zone as a case study. It will cover idiosyncrasies of how time zones are handled in Ruby and Rails, how to write tests to avoid false positives, and advice on how to release time zone-related code changes more safely.

This talk was presented at RailsConf 2015 in Atlanta, ~30 minutes: https://www.youtube.com/watch?v=VFDurYw6aZ8
Blog post: http://kwugirl.blogspot.com/2015/04/slightly-less-painful-time-zones.html

Transcript

1. Slightly Less Painful Time Zones Katherine Wu (KWu) @kwugirl. ! ! Software Engineer
2. ! @kwugirl why time is hard the problem the proposed solution the actual solution
3. ! @kwugirl why time is hard http://xkcd.com/1514/
4. ! @kwugirl https://twitter.com/endtwist/status/544598751449739265
5. ! @kwugirl wat
6. ! @kwugirl “in October 1582, since days 5..14 just do not exist.” http://guides.rubyonrails.org/v4.0.13/active_support_core_extensions.html#extensions-to-date
7. ! @kwugirl wat
8. ! @kwugirl
9. ! @kwugirl
10. ! @kwugirl falsehoods programmers believe about time http://infiniteundo.com/post/25326999628/falsehoods-programmers-believe-about-time http://infiniteundo.com/post/25509354022/more-falsehoods-programmers-believe-about-time
11. ! @kwugirl falsehoods programmers believe about time http://infiniteundo.com/post/25326999628/falsehoods-programmers-believe-about-time http://infiniteundo.com/post/25509354022/more-falsehoods-programmers-believe-about-time
12. ! @kwugirl falsehoods programmers believe about time • There are only 24 time zones. http://infiniteundo.com/post/25326999628/falsehoods-programmers-believe-about-time http://infiniteundo.com/post/25509354022/more-falsehoods-programmers-believe-about-time
13. ! @kwugirl falsehoods programmers believe about time • There are only 24 time zones. • Time zones always differ by a whole hour. http://infiniteundo.com/post/25326999628/falsehoods-programmers-believe-about-time http://infiniteundo.com/post/25509354022/more-falsehoods-programmers-believe-about-time
14. ! @kwugirl falsehoods programmers believe about time • There are only 24 time zones. • Time zones always differ by a whole hour. • Time always goes forwards. http://infiniteundo.com/post/25326999628/falsehoods-programmers-believe-about-time http://infiniteundo.com/post/25509354022/more-falsehoods-programmers-believe-about-time
15. ! @kwugirl
16. ! @kwugirl
17. ! @kwugirl wat
18. ! @kwugirl Lesson #1: Trust NOTHING
19. ! @kwugirl Lesson #1: Trust NOTHING (including Argentina)
20. ! @kwugirl
21. ! @kwugirl [1] pry(main)> 1.month == 30.days
22. ! @kwugirl [1] pry(main)> 1.month == 30.days => true
23. ! @kwugirl [1] pry(main)> 1.month == 30.days => true [2] pry(main)> Date.today
24. ! @kwugirl [1] pry(main)> 1.month == 30.days => true [2] pry(main)> Date.today => Thu, 09 Apr 2015
25. ! @kwugirl [1] pry(main)> 1.month == 30.days => true [2] pry(main)> Date.today => Thu, 09 Apr 2015 [3] pry(main)> Date.today - 1.month
26. ! @kwugirl [1] pry(main)> 1.month == 30.days => true [2] pry(main)> Date.today => Thu, 09 Apr 2015 [3] pry(main)> Date.today - 1.month => Mon, 09 Mar 2015
27. ! @kwugirl [1] pry(main)> 1.month == 30.days => true [2] pry(main)> Date.today => Thu, 09 Apr 2015 [3] pry(main)> Date.today - 1.month => Mon, 09 Mar 2015 [4] pry(main)> Date.today - 30.days
28. ! @kwugirl [1] pry(main)> 1.month == 30.days => true [2] pry(main)> Date.today => Thu, 09 Apr 2015 [3] pry(main)> Date.today - 1.month => Mon, 09 Mar 2015 [4] pry(main)> Date.today - 30.days => Tue, 10 Mar 2015
29. ! @kwugirl Lesson #1: Trust NOTHING (including Argentina)
30. ! @kwugirl Lesson #1: Trust NOTHING (including Argentina) (including math)
31. ! @kwugirl the problem
32. ! @kwugirl weekly email report
33. ! @kwugirl
34. ! @kwugirl cron job
35. ! @kwugirl cron job WeeklyEmailJob for account 1 WeeklyEmailJob for account 2 WeeklyEmailJob for account 3… enqueues
36. ! @kwugirl cron job WeeklyEmailJob for account 1 WeeklyEmailJob for account 2 WeeklyEmailJob for account 3… email for account 1 email for account 2 email for account 3… enqueues generates
37. ! @kwugirl cron job WeeklyEmailJob for account 1 WeeklyEmailJob for account 2 WeeklyEmailJob for account 3… email for account 1 email for account 2 email for account 3… enqueues SCHEDULING generates
38. ! @kwugirl cron job WeeklyEmailJob for account 1 WeeklyEmailJob for account 2 WeeklyEmailJob for account 3… email for account 1 email for account 2 email for account 3… enqueues SCHEDULING EXECUTING generates
39. ! @kwugirl cron job enqueues email for account 1 email for account 2 email for account 3… generates WeeklyEmailJob for account 1 WeeklyEmailJob for account 2 WeeklyEmailJob for account 3…
40. ! @kwugirl cron job enqueues Monday 10am Pacific time email for account 1 email for account 2 email for account 3… generates WeeklyEmailJob for account 1 WeeklyEmailJob for account 2 WeeklyEmailJob for account 3…
41. ! @kwugirl
42. ! @kwugirl however…
43. ! @kwugirl Monday 10am Pacific time == Tuesday 2am Tokyo Monday Tuesday
44. ! @kwugirl MOAR ACCOUNTS
45. ! @kwugirl MOAR ACCOUNTS
46. ! @kwugirl “Monday” report 
 received on Tuesday! Sun Mon Tues Wed Thurs Fri Sat
47. ! @kwugirl the proposed solution
48. ! @kwugirl set up report jobs to run Monday 1:01am local time Local time Pacific time WeeklyEmailJob for account 1 Mon 1:01am JST Sun 9:01am WeeklyEmailJob for account 2 Mon 1:01am EDT Sun 10:01pm WeeklyEmailJob for account 3 Mon 1:01am HAST Mon 4:01am
49. ! @kwugirl cron job WeeklyEmailJob for account 1 WeeklyEmailJob for account 2 WeeklyEmailJob for account 3… enqueues email for account 1 email for account 2 email for account 3… generates local
50. ! @kwugirl cron job WeeklyEmailJob for account 1 WeeklyEmailJob for account 2 WeeklyEmailJob for account 3… enqueues Saturday 10am Pacific time email for account 1 email for account 2 email for account 3… generates local
51. ! @kwugirl report processing spread out 0 25 50 75 100 8am PT 9am PT 10am PT 11am PT 12pm PT 1pm PT 2pm PT 3pm PT before
52. ! @kwugirl report processing spread out 0 25 50 75 100 8am PT 9am PT 10am PT 11am PT 12pm PT 1pm PT 2pm PT 3pm PT before 0 25 50 75 100 8am PT 9am PT 10am PT 11am PT 12pm PT 1pm PT 2pm PT 3pm PT after
53. ! @kwugirl first attempt
54. ! @kwugirl what date is the next Monday?
55. ! @kwugirl
56. ! @kwugirl [1] pry(main)> Date.today
57. ! @kwugirl [1] pry(main)> Date.today => Sun, 05 Apr 2015
58. ! @kwugirl [1] pry(main)> Date.today => Sun, 05 Apr 2015 [2] pry(main)> DateTime.parse("Monday, 1:01")
59. ! @kwugirl [1] pry(main)> Date.today => Sun, 05 Apr 2015 [2] pry(main)> DateTime.parse("Monday, 1:01") => Mon, 06 Apr 2015 01:01:00 +0000
60. ! @kwugirl how do I get that into 
 the local time zone?
61. ! @kwugirl Rails Time/Date classes
62. ! @kwugirl TZInfo daylight saving-aware time conversions
63. ! @kwugirl Internet Assigned Numbers Authority (IANA) Time Zone Database
64. ! @kwugirl April 2015 May 2012
65. ! @kwugirl ActiveRecord pins TZInfo version
66. ! @kwugirl ActiveRecord pins TZInfo version (need to upgrade Rails versions to get accurate data)
67. ! @kwugirl ActiveSupport::TimeZone
68. ! @kwugirl ActiveSupport::TimeZone TZInfo::Timezone instances
69. ! @kwugirl “a meaningful subset of 
 146 time zones” 
 (out of many more)
70. ! @kwugirl ~24 bands vs…
71. ! @kwugirl { "International Date Line West" => "Pacific/Midway", "Midway Island" => "Pacific/Midway", "American Samoa" => "Pacific/Pago_Pago", "Hawaii" => "Pacific/Honolulu", "Alaska" => "America/Juneau", "Pacific Time (US & Canada)" => "America/Los_Angeles", "Tijuana" => "America/Tijuana", "Mountain Time (US & Canada)" => "America/Denver", "Arizona" => "America/Phoenix", "Chihuahua" => "America/Chihuahua", "Mazatlan" => "America/Mazatlan", "Central Time (US & Canada)" => "America/Chicago", "Saskatchewan" => "America/Regina", "Guadalajara" => "America/Mexico_City", "Mexico City" => "America/Mexico_City", "Monterrey" => "America/Monterrey", "Central America" => "America/Guatemala", "Eastern Time (US & Canada)" => "America/New_York", "Indiana (East)" => "America/Indiana/Indianapolis", "Bogota" => "America/Bogota", "Lima" => "America/Lima", "Quito" => "America/Lima", "Atlantic Time (Canada)" => "America/Halifax", "Caracas" => "America/Caracas", "La Paz" => "America/La_Paz", "Santiago" => "America/Santiago", "Newfoundland" => "America/St_Johns", "Brasilia" => "America/Sao_Paulo", "Buenos Aires" => "America/Argentina/Buenos_Aires", "Montevideo" => "America/Montevideo", "Georgetown" => "America/Guyana", "Greenland" => "America/Godthab", "Mid-Atlantic" => "Atlantic/South_Georgia", "Azores" => "Atlantic/Azores", "Cape Verde Is." => "Atlantic/Cape_Verde", "Dublin" => "Europe/ Dublin", "Edinburgh" => "Europe/London", "Lisbon" => "Europe/Lisbon", "London" => "Europe/London", "Casablanca" => "Africa/Casablanca", "Monrovia" => "Africa/Monrovia", "UTC" => "Etc/UTC", "Belgrade" => "Europe/Belgrade", "Bratislava" => "Europe/Bratislava", "Budapest" => "Europe/Budapest", "Ljubljana" => "Europe/Ljubljana", "Prague" => "Europe/Prague", "Sarajevo" => "Europe/Sarajevo", "Skopje" => "Europe/Skopje", "Warsaw" => "Europe/Warsaw", "Zagreb" => "Europe/Zagreb", "Brussels" => "Europe/Brussels", "Copenhagen" => "Europe/Copenhagen", "Madrid" => "Europe/Madrid", "Paris" => "Europe/Paris", "Amsterdam" => "Europe/Amsterdam", "Berlin" => "Europe/Berlin", "Bern" => "Europe/ Berlin", "Rome" => "Europe/Rome", "Stockholm" => "Europe/Stockholm", "Vienna" => "Europe/Vienna", "West Central Africa" => "Africa/Algiers", "Bucharest" => "Europe/Bucharest", "Cairo" => "Africa/Cairo", "Helsinki" => "Europe/ Helsinki", "Kyiv" => "Europe/Kiev", "Riga" => "Europe/Riga", "Sofia" => "Europe/Sofia", "Tallinn" => "Europe/Tallinn", "Vilnius" => "Europe/Vilnius", "Athens" => "Europe/Athens", "Istanbul" => "Europe/Istanbul", "Minsk" => "Europe/ Minsk", "Jerusalem" => "Asia/Jerusalem", "Harare" => "Africa/Harare", "Pretoria" => "Africa/Johannesburg", "Kaliningrad" => "Europe/Kaliningrad", "Moscow" => "Europe/Moscow", "St. Petersburg" => "Europe/Moscow", "Volgograd" => "Europe/Volgograd", "Samara" => "Europe/Samara", "Kuwait" => "Asia/Kuwait", "Riyadh" => "Asia/Riyadh", "Nairobi" => "Africa/Nairobi", "Baghdad" => "Asia/Baghdad", "Tehran" => "Asia/Tehran", "Abu Dhabi" => "Asia/Muscat", "Muscat" => "Asia/Muscat", "Baku" => "Asia/Baku", "Tbilisi" => "Asia/Tbilisi", "Yerevan" => "Asia/Yerevan", "Kabul" => "Asia/Kabul", "Ekaterinburg" => "Asia/Yekaterinburg", "Islamabad" => "Asia/Karachi", "Karachi" => "Asia/Karachi", "Tashkent" => "Asia/Tashkent", "Chennai" => "Asia/Kolkata", "Kolkata" => "Asia/Kolkata", "Mumbai" => "Asia/Kolkata", "New Delhi" => "Asia/Kolkata", "Kathmandu" => "Asia/Kathmandu", "Astana" => "Asia/Dhaka", "Dhaka" => "Asia/Dhaka", "Sri Jayawardenepura" => "Asia/Colombo", "Almaty" => "Asia/Almaty", "Novosibirsk" => "Asia/Novosibirsk", "Rangoon" => "Asia/Rangoon", "Bangkok" => "Asia/Bangkok", "Hanoi" => "Asia/Bangkok", "Jakarta" => "Asia/Jakarta", "Krasnoyarsk" => "Asia/Krasnoyarsk", "Beijing" => "Asia/Shanghai", "Chongqing" => "Asia/Chongqing", "Hong Kong" => "Asia/Hong_Kong", "Urumqi" => "Asia/Urumqi", "Kuala Lumpur" => "Asia/Kuala_Lumpur", "Singapore" => "Asia/Singapore", "Taipei" => "Asia/ Taipei", "Perth" => "Australia/Perth", "Irkutsk" => "Asia/Irkutsk", "Ulaanbaatar" => "Asia/Ulaanbaatar", "Seoul" => "Asia/Seoul", "Osaka" => "Asia/Tokyo", "Sapporo" => "Asia/Tokyo", "Tokyo" => "Asia/Tokyo", "Yakutsk" => "Asia/ Yakutsk", "Darwin" => "Australia/Darwin", "Adelaide" => "Australia/Adelaide", "Canberra" => "Australia/Melbourne", "Melbourne" => "Australia/Melbourne", "Sydney" => "Australia/Sydney", "Brisbane" => "Australia/Brisbane", "Hobart" => "Australia/Hobart", "Vladivostok" => "Asia/Vladivostok", "Guam" => "Pacific/Guam", "Port Moresby" => "Pacific/Port_Moresby", "Magadan" => "Asia/Magadan", "Srednekolymsk" => "Asia/Srednekolymsk", "Solomon Is." => "Pacific/ Guadalcanal", "New Caledonia" => "Pacific/Noumea", "Fiji" => "Pacific/Fiji", "Kamchatka" => "Asia/Kamchatka", "Marshall Is." => "Pacific/Majuro", "Auckland" => "Pacific/Auckland", "Wellington" => "Pacific/Auckland", "Nuku'alofa" => "Pacific/Tongatapu", "Tokelau Is." => "Pacific/Fakaofo", "Chatham Is." => "Pacific/Chatham", "Samoa" => "Pacific/Apia" } ~24 bands vs…
72. ! @kwugirl friendlier zone names “Eastern Time (US & Canada)” vs “America/New_York”
73. ! @kwugirl getting time zone names
74. ! @kwugirl getting time zone names [1] pry(main)> ActiveSupport::TimeZone.zones_map.values.collect{|z| z.name if z.formatted_offset == "+12:00"}.compact!
75. ! @kwugirl getting time zone names [1] pry(main)> ActiveSupport::TimeZone.zones_map.values.collect{|z| z.name if z.formatted_offset == "+12:00"}.compact! => ["Fiji", "Kamchatka", "Marshall Is.", "Auckland", “Wellington"]
76. ! @kwugirl getting time zone names [1] pry(main)> ActiveSupport::TimeZone.zones_map.values.collect{|z| z.name if z.formatted_offset == "+12:00"}.compact! => ["Fiji", "Kamchatka", "Marshall Is.", "Auckland", “Wellington"] [2] pry(main)> ActiveSupport::TimeZone.zones_map.values.collect{|z| z.name if z.formatted_offset == "-11:00"}.compact!
77. ! @kwugirl getting time zone names [1] pry(main)> ActiveSupport::TimeZone.zones_map.values.collect{|z| z.name if z.formatted_offset == "+12:00"}.compact! => ["Fiji", "Kamchatka", "Marshall Is.", "Auckland", “Wellington"] [2] pry(main)> ActiveSupport::TimeZone.zones_map.values.collect{|z| z.name if z.formatted_offset == "-11:00"}.compact! => ["International Date Line West", "Midway Island", "American Samoa"]
78. ! @kwugirl (no UTC -12:00 offset)
79. ! @kwugirl (no UTC -12:00 offset) “The Baker and Howland islands are not there. 
 But as (wikipedia says) they are uninhabited, they would be a quite specific use case. 
 I don't think they're going to be added to TZInfo.” — dmathieu
 https://github.com/rails/rails/issues/11390
80. ! @kwugirl how do I get a DateTime 
 into the local time zone?
81. ! @kwugirl ActiveSupport::TimeZone ! local_to_utc(time, dst=true) Adjust the given time to the simultaneous time in UTC. Returns a Time.utc() instance. !
82. ! @kwugirl attempt #1’s code
83. ! @kwugirl attempt #1’s code def local_1am(account_time_zone)
84. ! @kwugirl attempt #1’s code def local_1am(account_time_zone) dt = DateTime.parse("Monday, 1:01”)
85. ! @kwugirl attempt #1’s code def local_1am(account_time_zone) dt = DateTime.parse("Monday, 1:01”) default = ActiveSupport::TimeZone['Pacific Time (US & Canada)']
86. ! @kwugirl attempt #1’s code def local_1am(account_time_zone) dt = DateTime.parse("Monday, 1:01”) default = ActiveSupport::TimeZone['Pacific Time (US & Canada)'] local_time_zone = account_time_zone || default

87. ! @kwugirl attempt #1’s code def local_1am(account_time_zone) dt = DateTime.parse("Monday, 1:01”) default = ActiveSupport::TimeZone['Pacific Time (US & Canada)'] local_time_zone = account_time_zone || default
 local_time_zone.local_to_utc(dt) end
88. ! @kwugirl attempt #1’s tests
89. ! @kwugirl
90. ! @kwugirl
91. ! @kwugirl context "enqueue time" do
92. ! @kwugirl context "enqueue time" do setup do
 saturday_pt = DateTime.parse("4th Apr 2015 10:05:00 AM -07:00")
 Timecop.freeze(saturday_pt)
 end

93. ! @kwugirl context "enqueue time" do setup do
 saturday_pt = DateTime.parse("4th Apr 2015 10:05:00 AM -07:00")
 Timecop.freeze(saturday_pt)
 end
 # your tests

94. ! @kwugirl context "enqueue time" do setup do
 saturday_pt = DateTime.parse("4th Apr 2015 10:05:00 AM -07:00")
 Timecop.freeze(saturday_pt)
 end
 # your tests
 teardown do
 Timecop.return
 end
 end
95. ! @kwugirl # Running: ! .. ! Finished in -37452054.639617s, -0.0000 runs/s, -0.0000 assertions/s. ! 2 runs, 4 assertions, 0 failures, 0 errors, 0 skips
96. ! @kwugirl # Running: ! .. ! Finished in -37452054.639617s, -0.0000 runs/s, -0.0000 assertions/s. ! 2 runs, 4 assertions, 0 failures, 0 errors, 0 skips
97. ! @kwugirl wat
98. ! @kwugirl
99. ! @kwugirl setup do
 saturday_pt = DateTime.parse("4th Apr 2015 10:05:00 AM -07:00")
 Timecop.freeze(saturday_pt)
 end

100. ! @kwugirl setup do
 saturday_pt = DateTime.parse("4th Apr 2015 10:05:00 AM -07:00")
 Timecop.freeze(saturday_pt)
 end
 should "be the next Monday 1:01am local time (west of UTC)" do
101. ! @kwugirl setup do
 saturday_pt = DateTime.parse("4th Apr 2015 10:05:00 AM -07:00")
 Timecop.freeze(saturday_pt)
 end
 should "be the next Monday 1:01am local time (west of UTC)" do mtn_tz = ActiveSupport::TimeZone["Mountain Time (US & Canada)"]
102. ! @kwugirl setup do
 saturday_pt = DateTime.parse("4th Apr 2015 10:05:00 AM -07:00")
 Timecop.freeze(saturday_pt)
 end
 should "be the next Monday 1:01am local time (west of UTC)" do mtn_tz = ActiveSupport::TimeZone["Mountain Time (US & Canada)"] expected = DateTime.parse("6th Apr 2015 01:01:00 AM -06:00")
103. ! @kwugirl setup do
 saturday_pt = DateTime.parse("4th Apr 2015 10:05:00 AM -07:00")
 Timecop.freeze(saturday_pt)
 end
 should "be the next Monday 1:01am local time (west of UTC)" do mtn_tz = ActiveSupport::TimeZone["Mountain Time (US & Canada)"] expected = DateTime.parse("6th Apr 2015 01:01:00 AM -06:00") assert_equal expected, local_1am(mtn_tz) end
104. ! @kwugirl UTC Mountain time Bangkok time
105. ! @kwugirl # Running: ! .. ! Finished in 0.059444s, 33.6451 runs/s, 33.6451 assertions/s ! 2 runs, 2 assertions, 0 failures, 0 errors, 0 skips
106. ! @kwugirl scheduling changes
107. ! @kwugirl before cron job enqueues Monday 10am Pacific time email for account 1 email for account 2 email for account 3… generates WeeklyEmailJob for account 1 WeeklyEmailJob for account 2 WeeklyEmailJob for account 3…
108. ! @kwugirl after cron job WeeklyEmailJob for account 1 WeeklyEmailJob for account 2 WeeklyEmailJob for account 3… enqueues Saturday 10am Pacific time email for account 1 email for account 2 email for account 3… generates local
109. ! @kwugirl start on Sat morning if pdt_day == SATURDAY base_email = 'script/run_weekly_email_report.rb' Async::Command::Bulk.new(base_email).enqueue end
110. ! @kwugirl queue up jobs with a time WeeklyEmailReportJob.new(account.id).enqueue_at(local_1am(tz))
111. ! @kwugirl
112. ! @kwugirl FAILURE
113. ! @kwugirl had to manually regenerate 
 all email reports
114. ! @kwugirl Lesson #2: Have a backup plan
115. ! @kwugirl unknown unknowns
116. ! @kwugirl
117. ! @kwugirl Lesson #3: Do an internal test run
118. ! @kwugirl so what happened?
119. ! @kwugirl that week’s emails were queued for 1:01am local time…last Monday
120. ! @kwugirl can’t tell whether it’s closest date or last date Sun Mon Tues Wed Thurs Fri Sat
121. ! @kwugirl [1] pry(main)> Date.today can’t tell whether it’s closest date or last date Sun Mon Tues Wed Thurs Fri Sat
122. ! @kwugirl [1] pry(main)> Date.today => Thu, 09 Apr 2015 can’t tell whether it’s closest date or last date Sun Mon Tues Wed Thurs Fri Sat
123. ! @kwugirl [1] pry(main)> Date.today => Thu, 09 Apr 2015 can’t tell whether it’s closest date or last date Sun Mon Tues Wed Thurs Fri Sat
124. ! @kwugirl [1] pry(main)> Date.today => Thu, 09 Apr 2015 [2] pry(main)> DateTime.parse("Monday 1:01") can’t tell whether it’s closest date or last date Sun Mon Tues Wed Thurs Fri Sat
125. ! @kwugirl [1] pry(main)> Date.today => Thu, 09 Apr 2015 [2] pry(main)> DateTime.parse("Monday 1:01") can’t tell whether it’s closest date or last date Sun Mon Tues Wed Thurs Fri Sat
126. ! @kwugirl [1] pry(main)> Date.today => Thu, 09 Apr 2015 [2] pry(main)> DateTime.parse("Monday 1:01") => Mon, 06 Apr 2015 01:01:00 +0000 can’t tell whether it’s closest date or last date Sun Mon Tues Wed Thurs Fri Sat
127. ! @kwugirl [1] pry(main)> Date.today => Thu, 09 Apr 2015 [2] pry(main)> DateTime.parse("Monday 1:01") => Mon, 06 Apr 2015 01:01:00 +0000 can’t tell whether it’s closest date or last date Sun Mon Tues Wed Thurs Fri Sat
128. ! @kwugirl Lesson #4: Today’s console results are not tomorrow’s console results
129. ! @kwugirl but…tests??
130. ! @kwugirl DateTime.parse not friends with Timecop
131. ! @kwugirl changed test setup
132. ! @kwugirl changed test setup saturday_pt = DateTime.parse("1st May 2015 10:05:00 AM -07:00")
133. ! @kwugirl changed test setup saturday_pt = DateTime.parse("1st May 2015 10:05:00 AM -07:00") Timecop.freeze(saturday_pt)
134. ! @kwugirl changed test setup saturday_pt = DateTime.parse("1st May 2015 10:05:00 AM -07:00") Timecop.freeze(saturday_pt) setting date to May 1st (Fri)! want to get May 4th (next Mon)
135. ! @kwugirl
136. ! @kwugirl [1] pry(#<SchedulingHelperTest>)> Time.now
137. ! @kwugirl [1] pry(#<SchedulingHelperTest>)> Time.now => 2015-05-01 10:05:00 -0700
 

138. ! @kwugirl [1] pry(#<SchedulingHelperTest>)> Time.now => 2015-05-01 10:05:00 -0700
 
 date set to May 1st
139. ! @kwugirl [1] pry(#<SchedulingHelperTest>)> Time.now => 2015-05-01 10:05:00 -0700
 
 [2] pry(#<SchedulingHelperTest>)> DateTime.parse("Monday, 1:01") date set to May 1st
140. ! @kwugirl [1] pry(#<SchedulingHelperTest>)> Time.now => 2015-05-01 10:05:00 -0700
 
 [2] pry(#<SchedulingHelperTest>)> DateTime.parse("Monday, 1:01") => Mon, 06 Apr 2015 01:01:00 +0000 date set to May 1st
141. ! @kwugirl [1] pry(#<SchedulingHelperTest>)> Time.now => 2015-05-01 10:05:00 -0700
 
 [2] pry(#<SchedulingHelperTest>)> DateTime.parse("Monday, 1:01") => Mon, 06 Apr 2015 01:01:00 +0000 date set to May 1st DateTime parses to Apr 6th?!?
142. ! @kwugirl
143. ! @kwugirl setup do
 saturday_pt = DateTime.parse("4th Apr 2015 10:05:00 AM -07:00")
 Timecop.freeze(saturday_pt)
 end
 should "be the next Monday 1:01am local time (west of UTC)" do mtn_tz = ActiveSupport::TimeZone["Mountain Time (US & Canada)"] expected = DateTime.parse("6th Apr 2015 01:01:00 AM -06:00") ! assert_equal expected, local_1am(mtn_tz) end
144. ! @kwugirl setup do
 saturday_pt = DateTime.parse("4th Apr 2015 10:05:00 AM -07:00")
 Timecop.freeze(saturday_pt)
 end
 should "be the next Monday 1:01am local time (west of UTC)" do mtn_tz = ActiveSupport::TimeZone["Mountain Time (US & Canada)"] expected = DateTime.parse("6th Apr 2015 01:01:00 AM -06:00") ! assert_equal expected, local_1am(mtn_tz) end
145. ! @kwugirl setup do
 saturday_pt = DateTime.parse("4th Apr 2015 10:05:00 AM -07:00")
 Timecop.freeze(saturday_pt)
 end
 should "be the next Monday 1:01am local time (west of UTC)" do mtn_tz = ActiveSupport::TimeZone["Mountain Time (US & Canada)"] expected = DateTime.parse("6th Apr 2015 01:01:00 AM -06:00") ! assert_equal expected, local_1am(mtn_tz) end Test only passed because happened to run in the same week of Apr 4th, not because of Timecop.freeze
146. ! @kwugirl
147. ! @kwugirl
148. ! @kwugirl
149. ! @kwugirl Lesson #5: Guard against writing false positive tests
150. ! @kwugirl actual solution
151. ! @kwugirl TDD, that’s a thing
152. ! @kwugirl setup do
 saturday_pt = DateTime.parse("4th Apr 2015 10:05:00 AM -07:00")
 Timecop.freeze(saturday_pt)
 end
 should "be the next Monday 1:01am local time (west of UTC)" do mtn_tz = ActiveSupport::TimeZone["Mountain Time (US & Canada)"] expected = DateTime.parse("6th Apr 2015 01:01:00 AM -06:00") ! assert_equal expected, local_1am(mtn_tz) end
153. ! @kwugirl setup do
 saturday_pt = DateTime.parse("8th Feb 2015 10:05:00 AM -07:00")
 Timecop.freeze(saturday_pt)
 end
 should "be the next Monday 1:01am local time (west of UTC)" do mtn_tz = ActiveSupport::TimeZone["Mountain Time (US & Canada)"] expected = DateTime.parse("10th Feb 2015 01:01:00 AM -06:00") ! assert_equal expected, local_1am(mtn_tz) end
154. ! @kwugirl setup do
 saturday_pt = DateTime.parse("8th Feb 2015 10:05:00 AM -07:00")
 Timecop.freeze(saturday_pt)
 end
 should "be the next Monday 1:01am local time (west of UTC)" do mtn_tz = ActiveSupport::TimeZone["Mountain Time (US & Canada)"] expected = DateTime.parse("10th Feb 2015 01:01:00 AM -06:00") assert_wday(expected, "Monday") ! assert_equal expected, local_1am(mtn_tz) end
155. ! @kwugirl # Running: ! FF ! Finished in 0.061686s, 32.4223 runs/s, 64.8445 assertions/s. ! 1) Failure: SchedulingHelperTest#test_: enqueue time should be the next Monday 1:01am local time (west of UTC). -Mon, 10 Feb 2015 01:01:00 -0600 +Mon, 06 Apr 2015 07:01:00 +0000 ! 2) Failure: SchedulingHelperTest#test_: enqueue time should be the next Monday 1:01am local time (east of UTC). -Mon, 10 Feb 2015 01:01:00 +0700 +Sun, 05 Apr 2015 18:01:00 +0000 ! ! 2 runs, 4 assertions, 2 failures, 0 errors, 0 skips
156. ! @kwugirl need another way to get “next Monday” 
 besides simple DateTime.parse
157. ! @kwugirl Lesson #2: Have a backup plan
158. ! @kwugirl might need to run script after Saturday, if Saturday job fails
159. ! @kwugirl Sun Mon Tues Wed Thurs Fri Sat
160. ! @kwugirl Sun Mon Tues Wed Thurs Fri Sat
161. ! @kwugirl Sun Mon Tues Wed Thurs Fri Sat
162. ! @kwugirl Sun Mon Tues Wed Thurs Fri Sat
163. ! @kwugirl Sun Mon Tues Wed Thurs Fri Sat
164. ! @kwugirl Sun Mon Tues Wed Thurs Fri Sat
165. ! @kwugirl Sun Mon Tues Wed Thurs Fri Sat
166. ! @kwugirl Sun Mon Tues Wed Thurs Fri Sat
167. ! @kwugirl Sun Mon Tues Wed Thurs Fri Sat
168. ! @kwugirl Sun Mon Tues Wed Thurs Fri Sat
169. ! @kwugirl Sun Mon Tues Wed Thurs Fri Sat
170. ! @kwugirl Sun Mon Tues Wed Thurs Fri Sat
171. ! @kwugirl distinguishing between “this” week and “next” week?
172. ! @kwugirl multiple time zones
173. ! @kwugirl multiple time zones • the time we’re used to thinking of (Pacific time)
174. ! @kwugirl multiple time zones • the time we’re used to thinking of (Pacific time) • server’s time zone (who even knows)
175. ! @kwugirl multiple time zones • the time we’re used to thinking of (Pacific time) • server’s time zone (who even knows) • the customer’s time zone (could be ahead of us or behind us when running script)
176. ! @kwugirl need logic to apply globally
177. ! @kwugirl if it’s still Monday somewhere, anywhere, we’ll think of it as “this” week still
178. ! @kwugirl once it’s at least Tuesday everywhere, script should schedule reports for the next Monday
179. ! @kwugirl Lesson #6: Figure out a consistent, global logic
180. ! @kwugirl
181. ! @kwugirl def local_1am(account_time_zone)
182. ! @kwugirl def local_1am(account_time_zone) last_day = ActiveSupport::TimeZone['International Date Line West'].today
183. ! @kwugirl def local_1am(account_time_zone) last_day = ActiveSupport::TimeZone['International Date Line West'].today days_until_monday = (8 - last_day.wday) % 7
184. ! @kwugirl def local_1am(account_time_zone) last_day = ActiveSupport::TimeZone['International Date Line West'].today days_until_monday = (8 - last_day.wday) % 7 next_monday = last_day + days_until_monday

185. ! @kwugirl def local_1am(account_time_zone) last_day = ActiveSupport::TimeZone['International Date Line West'].today days_until_monday = (8 - last_day.wday) % 7 next_monday = last_day + days_until_monday
 local_tz = account_time_zone || ActiveSupport::TimeZone['Pacific Time']
186. ! @kwugirl def local_1am(account_time_zone) last_day = ActiveSupport::TimeZone['International Date Line West'].today days_until_monday = (8 - last_day.wday) % 7 next_monday = last_day + days_until_monday
 local_tz = account_time_zone || ActiveSupport::TimeZone['Pacific Time'] current_tz_offset = local_timezone.formatted_offset
187. ! @kwugirl def local_1am(account_time_zone) last_day = ActiveSupport::TimeZone['International Date Line West'].today days_until_monday = (8 - last_day.wday) % 7 next_monday = last_day + days_until_monday
 local_tz = account_time_zone || ActiveSupport::TimeZone['Pacific Time'] current_tz_offset = local_timezone.formatted_offset like “+07:00”
188. ! @kwugirl def local_1am(account_time_zone) last_day = ActiveSupport::TimeZone['International Date Line West'].today days_until_monday = (8 - last_day.wday) % 7 next_monday = last_day + days_until_monday
 local_tz = account_time_zone || ActiveSupport::TimeZone['Pacific Time'] current_tz_offset = local_timezone.formatted_offset 
 DateTime.parse("#{next_monday} 01:01:00 AM #{current_tz_offset}") end
189. ! @kwugirl # Running: ! .. ! Finished in 0.041562s, 48.1209 runs/s, 96.2418 assertions/s. ! 2 runs, 4 assertions, 0 failures, 0 errors, 0 skips
190. ! @kwugirl MOAR TESTS
191. ! @kwugirl context "enqueue time" do context "during U.S. standard time" do… end ! context "during U.S. daylight saving" do… end
192. ! @kwugirl # Running: ! ..F. ! Finished in 0.061256s, 65.2997 runs/s, 130.5995 assertions/s. ! 1) Failure: SchedulingHelperTest#test_: enqueue time during U.S. daylight saving should be the next Monday 1:01am local time (west of UTC). --- expected +++ actual @@ -1 +1 @@ -Mon, 09 Jun 2014 01:01:00 -0600 +Mon, 09 Jun 2014 01:01:00 -0700 ! ! 4 runs, 8 assertions, 1 failures, 0 errors, 0 skips
193. ! @kwugirl # Running: ! ..F. ! Finished in 0.061256s, 65.2997 runs/s, 130.5995 assertions/s. ! 1) Failure: SchedulingHelperTest#test_: enqueue time during U.S. daylight saving should be the next Monday 1:01am local time (west of UTC). --- expected +++ actual @@ -1 +1 @@ -Mon, 09 Jun 2014 01:01:00 -0600 +Mon, 09 Jun 2014 01:01:00 -0700 ! ! 4 runs, 8 assertions, 1 failures, 0 errors, 0 skips off by 1…
194. ! @kwugirl def local_1am(account_time_zone) last_day = ActiveSupport::TimeZone['International Date Line West'].today days_until_monday = (8 - last_day.wday) % 7 next_monday = last_day + days_until_monday
 local_tz = account_time_zone || ActiveSupport::TimeZone['Pacific Time'] current_tz_offset = local_timezone.now.formatted_offset 
 DateTime.parse("#{next_monday} 01:01:00 AM #{current_tz_offset}") end
195. ! @kwugirl # Running: ! .... ! Finished in 0.043776s, 91.3743 runs/s, 182.7485 assertions/s. ! 4 runs, 8 assertions, 0 failures, 0 errors, 0 skips
196. ! @kwugirl Sun Mon Tues Wed Thurs Fri Sat
197. ! @kwugirl Sun Mon Tues Wed Thurs Fri Sat
198. ! @kwugirl context "when run on different days of the week" do setup do @samoa_tz = ActiveSupport::TimeZone[“American Samoa"] @wellington_tz = ActiveSupport::TimeZone["Wellington"] end
199. ! @kwugirl
200. ! @kwugirl should "be the next day when run on late Sunday night" do
201. ! @kwugirl should "be the next day when run on late Sunday night" do sunday_night = DateTime.parse("1st Jun 2014 11:30:00 PM #{@samoa_tz.formatted_offset}")
 Timecop.freeze(sunday_night)
 assert_wday(@samoa_tz.now, "Sunday")
202. ! @kwugirl should "be the next day when run on late Sunday night" do sunday_night = DateTime.parse("1st Jun 2014 11:30:00 PM #{@samoa_tz.formatted_offset}")
 Timecop.freeze(sunday_night)
 assert_wday(@samoa_tz.now, "Sunday")
203. ! @kwugirl should "be the next day when run on late Sunday night" do sunday_night = DateTime.parse("1st Jun 2014 11:30:00 PM #{@samoa_tz.formatted_offset}")
 Timecop.freeze(sunday_night)
 assert_wday(@samoa_tz.now, "Sunday") # It's already Monday in the customer account's time zone
 assert_wday(@wellington_tz.now, "Monday")

204. ! @kwugirl should "be the next day when run on late Sunday night" do sunday_night = DateTime.parse("1st Jun 2014 11:30:00 PM #{@samoa_tz.formatted_offset}")
 Timecop.freeze(sunday_night)
 assert_wday(@samoa_tz.now, "Sunday") # It's already Monday in the customer account's time zone
 assert_wday(@wellington_tz.now, "Monday")
 local_tz = ActiveSupport::TimeZone[@wellington_tz.name]
 expected = DateTime.parse("2nd Jun 2014 01:01:00 AM +12:00")

205. ! @kwugirl should "be the next day when run on late Sunday night" do sunday_night = DateTime.parse("1st Jun 2014 11:30:00 PM #{@samoa_tz.formatted_offset}")
 Timecop.freeze(sunday_night)
 assert_wday(@samoa_tz.now, "Sunday") # It's already Monday in the customer account's time zone
 assert_wday(@wellington_tz.now, "Monday")
 local_tz = ActiveSupport::TimeZone[@wellington_tz.name]
 expected = DateTime.parse("2nd Jun 2014 01:01:00 AM +12:00")
 assert_equal expected, local_1am(local_tz)
 end
206. ! @kwugirl # Running: ! ..... ! Finished in 0.059667s, 83.7984 runs/s, 201.1162 assertions/s. ! 5 runs, 12 assertions, 0 failures, 0 errors, 0 skips
207. ! @kwugirl
208. ! @kwugirl should "be the same week when still Monday somewhere" do
209. ! @kwugirl should "be the same week when still Monday somewhere" do monday = DateTime.parse("2nd Jun 2014 11:30:00 PM #{@samoa_tz.formatted_offset}")
 Timecop.freeze(monday)
 assert_wday(@samoa_tz.now, "Monday")
210. ! @kwugirl should "be the same week when still Monday somewhere" do monday = DateTime.parse("2nd Jun 2014 11:30:00 PM #{@samoa_tz.formatted_offset}")
 Timecop.freeze(monday)
 assert_wday(@samoa_tz.now, "Monday") 
 local_tz = ActiveSupport::TimeZone[@wellington_tz.name]

211. ! @kwugirl should "be the same week when still Monday somewhere" do monday = DateTime.parse("2nd Jun 2014 11:30:00 PM #{@samoa_tz.formatted_offset}")
 Timecop.freeze(monday)
 assert_wday(@samoa_tz.now, "Monday") 
 local_tz = ActiveSupport::TimeZone[@wellington_tz.name]
 expected = DateTime.parse("2nd Jun 2014 01:01:00 AM +12:00")
 assert_wday(expected, "Monday")
212. ! @kwugirl should "be the same week when still Monday somewhere" do monday = DateTime.parse("2nd Jun 2014 11:30:00 PM #{@samoa_tz.formatted_offset}")
 Timecop.freeze(monday)
 assert_wday(@samoa_tz.now, "Monday") 
 local_tz = ActiveSupport::TimeZone[@wellington_tz.name]
 expected = DateTime.parse("2nd Jun 2014 01:01:00 AM +12:00")
 assert_wday(expected, "Monday") 
 assert_equal expected, local_1am(local_tz) end
213. ! @kwugirl # Running: ! ...... ! Finished in 0.059173s, 101.3976 runs/s, 253.4940 assertions/s. ! 6 runs, 15 assertions, 0 failures, 0 errors, 0 skips
214. ! @kwugirl Sun Mon Tues Wed Thurs Fri Sat
215. ! @kwugirl
216. ! @kwugirl should "be the next week when run on Tuesday" do
217. ! @kwugirl should "be the next week when run on Tuesday" do tuesday = DateTime.parse("3rd Jun 2014 00:30:00 AM #{@samoa_tz.formatted_offset}")
 Timecop.freeze(tuesday)
 assert_wday(tuesday, "Tuesday")
218. ! @kwugirl should "be the next week when run on Tuesday" do tuesday = DateTime.parse("3rd Jun 2014 00:30:00 AM #{@samoa_tz.formatted_offset}")
 Timecop.freeze(tuesday)
 assert_wday(tuesday, "Tuesday") 
 local_tz = ActiveSupport::TimeZone[@wellington_tz.name]

219. ! @kwugirl should "be the next week when run on Tuesday" do tuesday = DateTime.parse("3rd Jun 2014 00:30:00 AM #{@samoa_tz.formatted_offset}")
 Timecop.freeze(tuesday)
 assert_wday(tuesday, "Tuesday") 
 local_tz = ActiveSupport::TimeZone[@wellington_tz.name]
 expected = DateTime.parse("9th Jun 2014 01:01:00 AM +12:00")
 assert_wday(expected, "Monday")

220. ! @kwugirl should "be the next week when run on Tuesday" do tuesday = DateTime.parse("3rd Jun 2014 00:30:00 AM #{@samoa_tz.formatted_offset}")
 Timecop.freeze(tuesday)
 assert_wday(tuesday, "Tuesday") 
 local_tz = ActiveSupport::TimeZone[@wellington_tz.name]
 expected = DateTime.parse("9th Jun 2014 01:01:00 AM +12:00")
 assert_wday(expected, "Monday")
 assert_equal expected, local_1am(local_tz) end
221. ! @kwugirl # Running: ! ....... ! Finished in 0.060848s, 115.0408 runs/s, 295.8191 assertions/s. ! 7 runs, 18 assertions, 0 failures, 0 errors, 0 skips
222. ! @kwugirl tests — Before • context "enqueue time" • should "be the next Monday 1:01am local time (west of UTC)" • should "be the next Monday 1:01am local time (east of UTC)"
223. ! @kwugirl tests — After • context "enqueue time" • context "during U.S. standard time” • should "be the next Monday 1:01am local time (west of UTC)" • should "be the next Monday 1:01am local time (east of UTC)" • context "during U.S. daylight saving” • should "be the next Monday 1:01am local time (west of UTC)" • should "be the next Monday 1:01am local time (east of UTC)” • context "when run on different days of the week" • should "be the next day when run on late Sunday night" • should "be the same week when still Monday somewhere" • should "be the next week when run on Tuesday"
224. ! @kwugirl tests to write • covering time zones west/east of UTC • pin down exactly when you’re starting and when you’re ending • pick random dates in the past or in the future--not current dates • test dates inside/outside daylight saving period • check that the dates being used in your tests are the expected day of the week • test when triggering the scripts on different days of the week • test on dates of daylight saving transitions
225. ! @kwugirl scheduling process changes
226. ! @kwugirl Lesson #2: Have a backup plan
227. ! @kwugirl keep option to trigger manually if @options[:enqueue_later] WeeklyEmailJob.new(id).enqueue_at(local_1am(tz)) else WeeklyEmailJob.new(id).enqueue end
228. ! @kwugirl Lesson #3: Do an internal test run
229. ! @kwugirl
230. ! @kwugirl # Test for enqueueing weekly emails jobs on Saturday if pdt_day == SATURDAY base = "script/run_weekly_email_report.rb"
231. ! @kwugirl # Test for enqueueing weekly emails jobs on Saturday if pdt_day == SATURDAY base = "script/run_weekly_email_report.rb" 
 options = " --account 3,10 --enqueue_later"
232. ! @kwugirl # Test for enqueueing weekly emails jobs on Saturday if pdt_day == SATURDAY base = "script/run_weekly_email_report.rb" 
 options = " --account 3,10 --enqueue_later" recipient = " --to \"kwu+emailtest@newrelic.com\""
233. ! @kwugirl # Test for enqueueing weekly emails jobs on Saturday if pdt_day == SATURDAY base = "script/run_weekly_email_report.rb" 
 options = " --account 3,10 --enqueue_later" recipient = " --to \"kwu+emailtest@newrelic.com\"" 
 test_email = [base, options, recipient].join("") Async::Command::Bulk.new(test_email).enqueue end
234. ! @kwugirl
235. ! @kwugirl
236. ! @kwugirl
237. ! @kwugirl lessons 1. Trust NOTHING! 2. Have a backup plan! 3. Do an internal test run! 4. Today’s console results are not 
 tomorrow’s console results ! 5. Guard against writing false positive tests! 6. Figure out a consistent, global logic