Add support for timezones to Active Job

Record what was the current timezone in effect when the job was
enqueued and then restore when the job is executed in same way
that the current locale is recorded and restored.

activejob/CHANGELOG.md

@@ -1,5 +1,13 @@
 ## Rails 6.0.0.alpha (Unreleased) ##
 
+*   Add support for timezones to Active Job
+
+    Record what was the current timezone in effect when the job was
+    enqueued and then restore when the job is executed in same way
+    that the current locale is recorded and restored.
+
+    *Andrew White*
+
 *   Rails 6 requires Ruby 2.4.1 or newer.
 
     *Jeremy Daer*

activejob/lib/active_job/base.rb

@@ -9,6 +9,7 @@ require "active_job/execution"
 require "active_job/callbacks"
 require "active_job/exceptions"
 require "active_job/logging"
+require "active_job/timezones"
 require "active_job/translation"
 
 module ActiveJob #:nodoc:
@@ -68,6 +69,7 @@ module ActiveJob #:nodoc:
     include Callbacks
     include Exceptions
     include Logging
+    include Timezones
     include Translation
 
     ActiveSupport.run_load_hooks(:active_job, self)

activejob/lib/active_job/core.rb

@@ -31,6 +31,9 @@ module ActiveJob
 
       # I18n.locale to be used during the job.
       attr_accessor :locale
+
+      # Timezone to be used during the job.
+      attr_accessor :timezone
     end
 
     # These methods will be included into any Active Job object, adding
@@ -87,7 +90,8 @@ module ActiveJob
         "priority"   => priority,
         "arguments"  => serialize_arguments(arguments),
         "executions" => executions,
-        "locale"     => I18n.locale.to_s
+        "locale"     => I18n.locale.to_s,
+        "timezone"   => Time.zone.try(:name)
       }
     end
 
@@ -125,6 +129,7 @@ module ActiveJob
       self.serialized_arguments = job_data["arguments"]
       self.executions           = job_data["executions"]
       self.locale               = job_data["locale"] || I18n.locale.to_s
+      self.timezone             = job_data["timezone"] || Time.zone.try(:name)
     end
 
     private

activejob/lib/active_job/timezones.rb

@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+module ActiveJob
+  module Timezones #:nodoc:
+    extend ActiveSupport::Concern
+
+    included do
+      around_perform do |job, block, _|
+        Time.use_zone(job.timezone, &block)
+      end
+    end
+  end
+end

activejob/test/cases/job_serialization_test.rb

@@ -54,4 +54,11 @@ class JobSerializationTest < ActiveSupport::TestCase
     job.provider_job_id = "some value set by adapter"
     assert_equal job.provider_job_id, job.serialize["provider_job_id"]
   end
+
+  test "serialize stores the current timezone" do
+    Time.use_zone "Hawaii" do
+      job = HelloJob.new
+      assert_equal "Hawaii", job.serialize["timezone"]
+    end
+  end
 end

activejob/test/cases/timezones_test.rb

@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+require "helper"
+require "jobs/timezone_dependent_job"
+
+class TimezonesTest < ActiveSupport::TestCase
+  setup do
+    JobBuffer.clear
+  end
+
+  test "it performs the job in the given timezone" do
+    job = TimezoneDependentJob.new("2018-01-01T00:00:00Z")
+    job.timezone = "London"
+    job.perform_now
+
+    assert_equal "Happy New Year!", JobBuffer.last_value
+
+    job = TimezoneDependentJob.new("2018-01-01T00:00:00Z")
+    job.timezone = "Eastern Time (US & Canada)"
+    job.perform_now
+
+    assert_equal "Just 5 hours to go", JobBuffer.last_value
+  end
+end

activejob/test/integration/queuing_test.rb

@@ -110,6 +110,22 @@ class QueuingTest < ActiveSupport::TestCase
     end
   end
 
+  test "current timezone is kept while running perform_later" do
+    skip if adapter_is?(:inline)
+
+    begin
+      current_zone = Time.zone
+      Time.zone = "Hawaii"
+
+      TestJob.perform_later @id
+      wait_for_jobs_to_finish_for(5.seconds)
+      assert job_executed
+      assert_equal "Hawaii", job_executed_in_timezone
+    ensure
+      Time.zone = current_zone
+    end
+  end
+
   test "should run job with higher priority first" do
     skip unless adapter_is?(:delayed_job, :que)
 

activejob/test/jobs/timezone_dependent_job.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+require_relative "../support/job_buffer"
+
+class TimezoneDependentJob < ActiveJob::Base
+  def perform(now)
+    now = now.in_time_zone
+    new_year = localtime(2018, 1, 1)
+
+    if now >= new_year
+      JobBuffer.add("Happy New Year!")
+    else
+      JobBuffer.add("Just #{(new_year - now).div(3600)} hours to go")
+    end
+  end
+
+  private
+
+    def localtime(*args)
+      Time.zone ? Time.zone.local(*args) : Time.utc(*args)
+    end
+end

activejob/test/support/integration/dummy_app_template.rb

@@ -21,6 +21,7 @@ class TestJob < ActiveJob::Base
     File.open(Rails.root.join("tmp/\#{x}.new"), "wb+") do |f|
       f.write Marshal.dump({
         "locale" => I18n.locale.to_s || "en",
+        "timezone" => Time.zone.try(:name) || "UTC",
         "executed_at" => Time.now.to_r
       })
     end

activejob/test/support/integration/test_case_helpers.rb

@@ -62,4 +62,8 @@ module TestCaseHelpers
     def job_executed_in_locale(id = @id)
       job_data(id)["locale"]
     end
+
+    def job_executed_in_timezone(id = @id)
+      job_data(id)["timezone"]
+    end
 end