Just in time

An overview of time zones in Rails. And handle multiple user-defined time zones in Rails with scheduled background workers, with an example of a time zones feature.

Presented at Ruby Brighton, July 20, 2015

Transcript

1. Just in Time A case study in time zones Elle Meredith @aemeredith Just in time
2. 4 Touch on time related libraries Just in time
3. 4 Touch on time related libraries 4 Setup Rails to work with user's time_zone Just in time
4. 4 Touch on time related libraries 4 Setup Rails to work with user's time zone 4 Play with Time in Rails Just in time
5. 4 Touch on time related libraries 4 Setup Rails to work with user's time zone 4 Play with Time in Rails 4 Introduce a feature and work through it Just in time
6. Time DateTime Just in time
7. TZInfo Ruby timezone library, which provides daylight savings aware transformations between times in different timezones. Just in time
8. > TZInfo::Timezone.all.count => 582 Just in time
9. > TZInfo::Timezone.all.count => 582 > TZInfo::Country.get("GB").zone_identifiers => ["Europe/London"] Just in time
10. > TZInfo::Timezone.all.count => 582 > TZInfo::Country.get("GB").zone_identifiers => ["Europe/London"] > TZInfo::Country.get("AU").zone_identifiers => ["Australia/Lord_Howe", "Antarctica/Macquarie", "Australia/Hobart", ... Just in time
11. > TZInfo::Timezone.all.count => 582 > TZInfo::Country.get("GB").zone_identifiers => ["Europe/London"] > TZInfo::Country.get("AU").zone_identifiers => ["Australia/Lord_Howe", "Antarctica/Macquarie", "Australia/Hobart", ... > TZInfo::Country.get("US").zone_identifiers.count => 29 Just in time
12. ActiveSupport ::TimeZone Just in time
13. Limit the set of zones provided by TZInfo to a meaningful subset of 146 zones Just in time
14. Friendlier zones "America/New_York" => "Eastern Time (US & Canada)" Just in time
15. ActiveSupport ::TimeWithZone Just in time
16. $ rake time:zones:all * UTC -11:00 * American Samoa International Date Line West Midway Island Samoa * UTC -10:00 * Hawaii * UTC -09:00 * Alaska ... Just in time
17. Checking current time zone # in console > Time.zone => #<ActiveSupport::TimeZone:0x007fbf46947b38 @current_period=#<TZInfo::TimezonePeriod: nil,nil,#<TZInfo::TimezoneOffset: 0,0,UTC>>>, @name="UTC", @tzinfo=#<TZInfo::TimezoneProxy: Etc/UTC>, @utc_offset=nil> Just in time
18. Setting a custom time zone # in console > Time.zone = "Perth" Just in time
19. Setting a custom time zone # in console > Time.zone = "Perth" # in config/application.rb config.time_zone = "Perth" Just in time
20. Setting a custom time zone # in console > Time.zone = "Perth" # in config/application.rb config.time_zone = "Perth" # ^ the default is "utc" Just in time
21. Stick with UTC Just in time
22. With user time zones create_table :users do |t| t.string :time_zone, default: "UTC" ... end Just in time
23. With user time zones 4 No: enums 4 Yes: strings Just in time
24. With user time zones: forms # Simple Form <%= f.input :time_zone %> Just in time
25. With user time zones: setting # app/controllers/application_controller.rb around_action :set_time_zone, if: :current_user private def set_time_zone(&block) Time.use_zone(current_user.time_zone, &block) end Just in time
26. With user time zones: displaying <%= time.in_time_zone(curent_user.time_zone) %> Just in time
27. ISO8601 and APIs > time = Time.now.utc.iso8601 => "2015-07-04T21:53:23Z" Just in time
28. ISO8601 and APIs > time = Time.now.utc.iso8601 => "2015-07-04T21:53:23Z" > Time.iso8601(time) => 2015-07-04 21:53:23 UTC Just in time
29. 3 different times 4 System time 4 Application time 4 Database time Just in time
30. > Time.zone.name => "UTC" Just in time
31. > Time.zone.name => "UTC" > Time.now => 2015-07-04 17:53:23 -0400 Just in time
32. > Time.zone.name => "UTC" > Time.now => 2015-07-04 17:53:23 -0400 > Time.zone = "Fiji" => "Fiji" Just in time
33. > Time.zone.name => "UTC" > Time.now => 2015-07-04 17:53:23 -0400 > Time.zone = "Fiji" => "Fiji" > Time.zone.name => "Fiji" Just in time
34. > Time.zone.name => "UTC" > Time.now => 2015-07-04 17:53:23 -0400 > Time.zone = "Fiji" => "Fiji" > Time.zone.name => "Fiji" > Time.now => 2015-07-04 17:53:37 -0400 Just in time
35. > Time.zone.name => "UTC" > Time.now => 2015-07-04 17:53:23 -0400 > Time.zone = "Fiji" => "Fiji" > Time.zone.name => "Fiji" > Time.now => 2015-07-04 17:53:37 -0400 > Time.zone.now Just in time
36. > Time.zone.name => "UTC" > Time.now => 2015-07-04 17:53:23 -0400 > Time.zone = "Fiji" => "Fiji" > Time.zone.name => "Fiji" > Time.now => 2015-07-04 17:53:37 -0400 > Time.zone.now => Sun, 05 Jul 2015 09:53:42 FJT +12:00 Just in time
37. > Time.zone = "Fiji" => "Fiji" > Time.zone.name => "Fiji" > Time.now => 2015-07-04 17:53:37 -0400 > Time.zone.now => Sun, 05 Jul 2015 09:53:42 FJT +12:00 > Time.current Just in time
38. > Time.zone.name => "Fiji" > Time.now => 2015-07-04 17:53:37 -0400 > Time.zone.now => Sun, 05 Jul 2015 09:53:42 FJT +12:00 > Time.current => Sun, 05 Jul 2015 09:54:17 FJT +12:00 Just in time
39. > Time.zone = "Fiji" => "Fiji" > Time.zone.name => "Fiji" > Time.now => 2015-07-04 17:53:37 -0400 > Time.zone.now => Sun, 05 Jul 2015 09:53:42 FJT +12:00 > Time.current => Sun, 05 Jul 2015 09:54:17 FJT +12:00 > Time.now.in_time_zone => Sun, 05 Jul 2015 09:56:57 FJT +12:00 Just in time
40. > Time.zone.name => "Fiji" Just in time
41. > Time.zone.name => "Fiji" > Date.today => Sat, 04 Jul 2015 Just in time
42. > Time.zone.name => "Fiji" > Date.today => Sat, 04 Jul 2015 > Time.zone.today => Sun, 05 Jul 2015 Just in time
43. > Time.zone.name => "Fiji" > Date.today => Sat, 04 Jul 2015 > Time.zone.today => Sun, 05 Jul 2015 > Time.zone.tomorrow => Mon, 06 Jul 2015 Just in time
44. > Time.zone.name => "Fiji" > Date.today => Sat, 04 Jul 2015 > Time.zone.today => Sun, 05 Jul 2015 > Time.zone.tomorrow => Mon, 06 Jul 2015 > 1.day.from_now => Mon, 06 Jul 2015 10:00:56 FJT +12:00 Just in time
45. Time zone related querying Post.where("published_at > ?", Time.current) # SELECT "posts".* FROM "posts" # WHERE (published_at > # '2015-07-04 17:45:01.452465') Just in time
46. DON'T * Time.now DO * Time.current * 2.hours.ago Just in time
47. DON'T * Date.today * Date.today.to_time DO * Time.zone.today * 1.day.from_now Just in time
48. DON'T * Time.parse("2015-07-04 17:05:37") * Time.strptime(string, "%Y-%m-%dT%H:%M:%S%z") DO * Time.zone.parse("2015-07-04 17:05:37") * Time.strptime( string, "%Y-%m-%dT%H:%M:%S%z" ).in_time_zone Just in time
49. Testing time zones ActiveSupport::Testing::TimeHelpers travel_to 1.day do # do something tomorrow end travel_back Just in time
50. Testing time zones: gems # Timecop Timecop.freeze new_time Timecop.travel new_time Timecop.return Time.use_zone("Sydney") do … end # Delorean Delorean.time_travel_to("1 month ago") do … end Delorean.back_to_the_present # Zonebie Zonebie.set_random_timezone Just in time
51. Recent Project Just in time
52. First go 4 Test suites that needed to run daily or weekly, 4 at a set time (1AM or 2AM), 4 and use ResqueScheduler to set the schedule to run the background workers. Just in time
53. ScheduleRule Just in time
54. ResqueScheduler # config/resque_schedule.yml weekly_test: cron: "0 1 * * 0" class: ScheduledWeeklyRunsWorker args: description: 'Run test suites weekly' daily_test: cron: "0 2 * * *" class: ScheduledDailyRunsWorker args: description: 'Run test suites daily' Just in time
55. Cron Syntax * * * * * command to execute ┬ ┬ ┬ ┬ ┬ │ │ │ │ │ │ │ │ │ │ │ │ │ │ └───── day of week (0 - 7) from Sunday │ │ │ └────────── month (1 - 12) │ │ └─────────────── day of month (1 - 31) │ └──────────────────── hour (0 - 23) └───────────────────────── min (0 - 59) Just in time
56. So what was the problem? The scheduled tests were running at 2AM AEST regardless of the user’s time zone. Just in time
57. Second go 4 Test runs according to user's settings, at a specific week day, hour, and time zone. Just in time
58. Second go 4 Test runs according to user's settings, at a specific week day, hour, and time zone. 4 ResqueScheduler to run hourly and look for test suites that are due to run. Just in time
59. Second go 4 Test runs according to user's settings, at a specific week day, hour, and time zone. 4 ResqueScheduler to run hourly and look for test suites that are due to run. 4 The ResqueScheduler to look for test runs where the background job failed and thus due to be run as well. Just in time
60. ScheduleRule.rb every: string, wday: integer, hour: integer, time_zone: string, last_scheduled_run_at: timestamp, suite: references, ... Just in time
61. Still second go # lib/extensions.rb module ActiveSupport class TimeZone def self.current_zones(hour) all.select { |zone| t = Time.current.in_time_zone(zone) t.hour == hour }.map(&:tzinfo).map(&:name) end end end Just in time
62. Still second go # app/models/schedule_rule.rb class ScheduleRule < ActiveRecord::Base def self.find_rules(options={}) hour = options[:hour] where(zone: ActiveSupport::TimeZone.current_zones(hour)). where(options) end def self.suites_to_run(time_ago=Time.current, options={}) find_rules(options). older_than(time_ago). map(&:suite) end end Just in time
63. Still second go # app/workers/scheduled_runs_worker.rb class ScheduledRunsWorker def self.perform ScheduleRule. run_scheduled. daily. suites_to_run(yesterday, {hour: Time.now.utc.hour}) end end Just in time
64. Can we do better? Just in time
65. Meet hour in utc Just in time
66. Third go 4 Remove the .current_zones method. 4 Introduce the :hour_in_utc column in ScheduleRule class. Just in time
67. Third go class AddHourInUtc < ActiveRecord::Migration def change add_column :schedule_rules, :hour_in_utc, :integer end end Just in time
68. Still third go # app/models/schedule_rule.rb class ScheduleRule < ActiveRecord::Base before_save :set_hour_in_utc private def set_hour_in_utc self.hour_in_utc = ActiveSupport::TimeZone[zone]. parse("#{hour}:00:00"). utc. hour end end Just in time
69. Still third go # app/models/schedule_rule.rb class ScheduleRule < ActiveRecord::Base def self.suites_to_run(time_ago=Time.current, options={}) where(options). older_than(time_ago). map(&:suite) end end Just in time
70. Worker didn't change # app/workers/scheduled_runs_worker.rb class ScheduledRunsWorker def self.perform ScheduleRule. run_scheduled. daily. suites_to_run(yesterday, {hour: Time.now.utc.hour}) end end Just in time
71. Previously # app/models/schedule_rule.rb class ScheduleRule < ActiveRecord::Base def self.find_rules(options={}) hour = options[:hour] where(zone: ActiveSupport::TimeZone.current_zones(hour)). where(options) end def self.suites_to_run(time_ago=Time.current, options={}) find_rules(options). older_than(time_ago). map(&:suite) end end Just in time
72. Currently class ScheduleRule < ActiveRecord::Base def self.suites_to_run(time_ago=Time.current, options={}) where(options). older_than(time_ago). map(&:suite) end end Just in time
73. Always work with UTC Just in time
74. A couple more takeaways 4 Use Time.current or Time.zone.today. 4 Use testing helper methods of your choice to freeze the time in your tests, preferably by using a block. Just in time
75. Thanks! 4 robots.thoughtbot.com 4 speakerdeck.com/aemeredith 4 @aemeredith Just in time