Sub second resolution

lib/resque/plugins/priority_queue.rb

@@ -2,8 +2,9 @@ module Resque
   module Plugins
     module PriorityQueue
 
-      # the score is stored as the priority * multiplier + time.now.to_i, so that "ties" are handled correctly
-      PRIORITY_MULTIPLIER = (1e13).to_i
+      # the score is stored as the priority + the fraction of a century since Jan 1, 2012, so that "ties" are handled correctly
+      One_century = 100*365*24*60*60
+      Jan_1_2012  = Time.utc(2012).to_f
 
       MIN_PRIORITY = 0
       MAX_PRIORITY = 1000
@@ -129,7 +130,7 @@ def clean_priority(sym)
 
         # given a job score (from the zset), returns { :priority => cleaned priority, :created_at => unix timestamp }
         def job_score_parts(score)
-          { :priority => (score.to_i / PRIORITY_MULTIPLIER), :created_at => (score.to_i % PRIORITY_MULTIPLIER) }
+          { :priority => score.to_i, :created_at => unpack_timestamp(score.to_f) }
         end
 
         protected
@@ -161,9 +162,17 @@ def peek_priority(queue, start=0, count=1)
 
         end
 
+        def pack_timestamp(ts)
+          (ts-Jan_1_2012)/One_century
+        end
+
+        def unpack_timestamp(f)
+          Jan_1_2012 + (f-f.floor)*One_century
+        end
+
         # given a priority, calculate the final score to be used when adding the job to the queue zset
         def calculate_job_score(priority)
-          (clean_priority(priority) * PRIORITY_MULTIPLIER) + Time.now.to_i
+          clean_priority(priority) + pack_timestamp(Time.now.to_f)
         end
 
       end

test/job_test.rb

@@ -25,7 +25,7 @@ def test_create_with_priority
     Resque::Job.create_with_priority(:priority_jobs, SomePriorityJob, 75)
 
     # we actually store 1000 minus the priority
-    assert_equal 925, Resque.redis.zscore("queue:priority_jobs", Resque.encode(:class => 'SomePriorityJob', :args => [])).to_i / Resque::Plugins::PriorityQueue::PRIORITY_MULTIPLIER
+    assert_equal 925, Resque.redis.zscore("queue:priority_jobs", Resque.encode(:class => 'SomePriorityJob', :args => [])).to_i
 
     @worker.work(0)
 
@@ -36,11 +36,11 @@ def test_create_or_update_priority
     Resque::Job.create_or_update_priority(:priority_jobs, SomePriorityJob, 75)
 
     # we actually store 1000 minus the priority
-    assert_equal 925, Resque.redis.zscore("queue:priority_jobs", Resque.encode(:class => 'SomePriorityJob', :args => [])).to_i / Resque::Plugins::PriorityQueue::PRIORITY_MULTIPLIER
+    assert_equal 925, Resque.redis.zscore("queue:priority_jobs", Resque.encode(:class => 'SomePriorityJob', :args => [])).to_i
 
     Resque::Job.create_or_update_priority(:priority_jobs, SomePriorityJob, 975)
     # we store 1000 minus the priority
-    assert_equal 25, Resque.redis.zscore("queue:priority_jobs", Resque.encode(:class => SomePriorityJob, :args => [])).to_i / Resque::Plugins::PriorityQueue::PRIORITY_MULTIPLIER
+    assert_equal 25, Resque.redis.zscore("queue:priority_jobs", Resque.encode(:class => SomePriorityJob, :args => [])).to_i
   end
 
   def test_job_instance_priority

test/resque_test.rb

@@ -23,7 +23,7 @@ def test_push_with_priority
     Resque.push_with_priority(:priority_jobs, job, 75)
 
     # we actually store 1000 minus the priority
-    assert_equal 925, Resque.redis.zscore('queue:priority_jobs', Resque.encode(job)).to_i / Resque::Plugins::PriorityQueue::PRIORITY_MULTIPLIER
+    assert_equal 925, Resque.redis.zscore('queue:priority_jobs', Resque.encode(job)).to_i
 
   end
 
@@ -37,7 +37,7 @@ def test_push
     Resque.push(:priority_jobs, new_job)
 
     # should also add priority to the job
-    assert_equal 500, Resque.redis.zscore('queue:priority_jobs', Resque.encode(new_job)).to_i / Resque::Plugins::PriorityQueue::PRIORITY_MULTIPLIER
+    assert_equal 500, Resque.redis.zscore('queue:priority_jobs', Resque.encode(new_job)).to_i
 
     # a regular push to a queue that hasn't been initialized with priority should be a normal set
     non_priority_job = { :class => SomeNonPriorityJob, :args => [] }
@@ -170,12 +170,19 @@ def test_priority_enabled?
   end
 
   def test_calculate_job_score
-    @fake_now = Time.now
-    Time.stubs(:now).returns(@fake_now)
-
-    assert_equal (Resque::Plugins::PriorityQueue::PRIORITY_MULTIPLIER * 500 + @fake_now.to_i), Resque.send(:calculate_job_score, :normal)
-    assert_equal (@fake_now.to_i), Resque.send(:calculate_job_score, :highest)
-    assert_equal (Resque::Plugins::PriorityQueue::PRIORITY_MULTIPLIER * 223 + @fake_now.to_i), Resque.send(:calculate_job_score, 777)
+    # The whole part of the priority should equal the (inverse) specified priority
+    assert_equal 500, Resque.send(:calculate_job_score, :normal).to_i
+    assert_equal   0, Resque.send(:calculate_job_score,:highest).to_i
+    assert_equal 223, Resque.send(:calculate_job_score,     777).to_i
+
+    # The fractional part should encode creation order.
+    # The job_score should distinguish (and properly order) timestamp differences 
+    # down to a millisecond, provided that the system clock can.
+    a = Resque.send(:calculate_job_score,:normal)
+    t = Time.now+0.001
+    sleep 0.0001 until Time.now > t
+    b = Resque.send(:calculate_job_score,:normal)
+    assert a < b
 
   end
 

test/test_helper.rb

@@ -1,3 +1,4 @@
+require 'rubygems'
 require 'test/unit'
 require 'mocha'
 require 'resque'