Pseudo-Randomize "every hour" and "every day"

README.md

@@ -52,6 +52,10 @@ Run `whenever --help` for a complete list of options for selecting the schedule
 ### Example schedule.rb file
 
 ```ruby
+# randomize all :hour- and :day-jobs, when no specific at-time is given.
+# This avoids hourly jobs starting at the same time.
+# set :randomize, true
+
 every 3.hours do # 1.minute 1.day 1.week 1.month 1.year is also supported
   # the following tasks are run in parallel (not in sequence)
   runner "MyModel.some_process"
@@ -71,6 +75,10 @@ every :hour do # Many shortcuts available: :hour, :day, :month, :year, :reboot
   runner "SomeModel.ladeeda"
 end
 
+every :hour, randomize: true do # each hour, but at random minute
+  runner "SomeModel.ladeeda"
+end
+
 every :sunday, at: '12pm' do # Use any day of the week or :weekend, :weekday
   runner "Task.do_something_great"
 end

lib/whenever/cron.rb

@@ -7,6 +7,10 @@ class Cron
       MONTHS = %w(jan feb mar apr may jun jul aug sep oct nov dec)
       KEYWORDS = [:reboot, :yearly, :annually, :monthly, :weekly, :daily, :midnight, :hourly]
       REGEX = /^(@(#{KEYWORDS.join '|'})|((\*?[\d\/,\-]*)\s){3}(\*?([\d\/,\-]|(#{MONTHS.join '|'}))*\s)(\*?([\d\/,\-]|(#{DAYS.join '|'}))*))$/i
+      RANGE_FOR_RANDOM_BY_TIME_UNIT = {
+        minute: (0...60).to_a,
+        hour:   %w[22 23 00 01 02 03 04 05 06 07]
+      }.freeze
 
       attr_accessor :time, :task
 
@@ -16,6 +20,7 @@ def initialize(time = nil, task = nil, at = nil, options = {})
         @at_given = at
         @time = time
         @task = task
+        at    = Cron.randomize_at_by_task(at, time, options[:task]) if options[:randomize]
         @at   = at.is_a?(String) ? (Chronic.parse(at, chronic_options) || 0) : (at || 0)
       end
 
@@ -42,6 +47,28 @@ def self.output(times, job, options = {})
         end
       end
 
+      # pseudo-random: same at for same task, useful for debugging across several deploys
+      def self.randomize_at_by_task(at, time, task)
+        return at unless at.nil?
+
+        # atm, the randomizing-feature works only for symbols :hour and :day
+        # return at unless time.is_a?(Symbol) && [:hour, :day].include?(time)
+        case time
+        when :hour
+          random_by_task(task, :minute)
+        when :day
+          random_by_task(task, :hour) + ':' + random_by_task(task, :minute).to_s
+        else
+          at
+        end
+
+      end
+
+      def self.random_by_task(task, time_unit)
+        array = RANGE_FOR_RANDOM_BY_TIME_UNIT[time_unit]
+        array[task.sum % array.length]
+      end
+
       def output
         [time_in_cron_syntax, task].compact.join(' ').strip
       end

lib/whenever/job.rb

@@ -2,7 +2,7 @@
 
 module Whenever
   class Job
-    attr_reader :at, :roles, :mailto
+    attr_reader :at, :roles, :mailto, :options
 
     def initialize(options = {})
       @options = options

lib/whenever/job_list.rb

@@ -142,7 +142,7 @@ def cron_jobs_of_time(time, jobs)
         next unless roles.empty? || roles.any? do |r|
           job.has_role?(r)
         end
-        Whenever::Output::Cron.output(time, job, :chronic_options => @chronic_options) do |cron|
+        Whenever::Output::Cron.output(time, job, job.options.merge(:chronic_options => @chronic_options)) do |cron|
           cron << "\n\n"
 
           if cron[0,1] == "@"

test/functional/output_random_at_test.rb

@@ -0,0 +1,53 @@
+require 'test_helper'
+
+class OutputRandomAtTest < Whenever::TestCase
+  test "pseudo random at for hour and day" do
+    output = Whenever.cron \
+    <<-file
+      set :job_template, nil
+      set :randomize, true
+      every :day do
+        command "blahblah"
+      end
+    file
+    assert_match '34 2 * * * blahblah', output
+
+    output = Whenever.cron \
+    <<-file
+      set :job_template, nil
+      set :randomize, true
+      every :day do
+        runner "blahblah"
+      end
+    file
+    assert_match(/\A34 2 * * */, output)
+
+    output = Whenever.cron \
+    <<-file
+      set :job_template, nil
+      every :day, randomize: true do
+        command "blah"
+      end
+    file
+    assert_match '47 5 * * * blah', output
+
+    output = Whenever.cron \
+    <<-file
+      set :job_template, nil
+      set :randomize, true
+      every :hour do
+        command "blahblah"
+      end
+    file
+    assert_match '34 * * * * blahblah', output
+
+    output = Whenever.cron \
+    <<-file
+      set :job_template, nil
+      every :hour, randomize: true do
+        command "blah"
+      end
+    file
+    assert_match '47 * * * * blah', output
+  end
+end