Preserve job ordering

lib/resque-lonely_job.rb

@@ -23,10 +23,18 @@ def unlock_queue(*args)
         Resque.redis.del(redis_key(*args))
       end
 
+      # Unfortunately, there's not a Resque interface for lpush so we have to
+      # role our own.  This is based on Resque.push but we don't need to
+      # call Resque.watch_queue as the queue should already exist if we're
+      # unable to get the lock.
+      def lpush(*args)
+        Resque.redis.lpush("queue:#{Resque.queue_from_class(self)}", Resque.encode(class: self, args: args))
+      end
+
       def before_perform(*args)
         unless can_lock_queue?(*args)
-          # can't get the lock, so place self at the end of the queue
-          Resque.enqueue(self, *args)
+          # can't get the lock, so place at the front of the queue
+          lpush(*args)
 
           # and don't perform
           raise Resque::Job::DontPerform

spec/lib/lonely_job_spec.rb

@@ -65,18 +65,19 @@ def self.perform(account_id, *args); end
         -> { job.perform }.should raise_error(Exception)
       end
 
-      it 'should place self at the end of the queue if unable to acquire the lock' do
-        Resque.size(:serial_work).should == 0
-
-        job = Resque::Job.new(:serial_work, { 'class' => 'SerialJob', 'args' => %w[account_one job_one] })
+      it 'should place self at the beginning of the queue if unable to acquire the lock' do
+        job1 = Resque::Job.create(:serial_work, 'SerialJob', %w[account_one job_one])
+        job2 = Resque::Job.create(:serial_work, 'SerialJob', %w[account_one job_two])
 
         SerialJob.should_receive(:can_lock_queue?).and_return(false)
 
         # perform returns false when DontPerform exception is raised in
         # before_perform callback
-        job.perform.should be_false
+        job1 = Resque.reserve(:serial_work)
+        job1.perform.should be_false
 
-        Resque.size(:serial_work).should == 1
+        first_queue_element = Resque.reserve(:serial_work)
+        first_queue_element.should == job1
       end
     end
 
@@ -110,18 +111,19 @@ def self.perform(account_id, *args); end
         -> { job.perform }.should raise_error(Exception)
       end
 
-      it 'should place self at the end of the queue if unable to acquire the lock' do
-        Resque.size(:serial_work).should == 0
-
-        job = Resque::Job.new(:serial_work, { 'class' => 'SerialJobWithCustomRedisKey', 'args' => %w[account_one job_one] })
+      it 'should place self at the beginning of the queue if unable to acquire the lock' do
+        job1 = Resque::Job.create(:serial_work, 'SerialJobWithCustomRedisKey', %w[account_one job_one])
+        job2 = Resque::Job.create(:serial_work, 'SerialJobWithCustomRedisKey', %w[account_one job_two])
 
         SerialJobWithCustomRedisKey.should_receive(:can_lock_queue?).and_return(false)
 
         # perform returns false when DontPerform exception is raised in
         # before_perform callback
-        job.perform.should be_false
+        job1 = Resque.reserve(:serial_work)
+        job1.perform.should be_false
 
-        Resque.size(:serial_work).should == 1
+        first_queue_element = Resque.reserve(:serial_work)
+        first_queue_element.should == job1
       end
     end
   end