Improve performance by usually starting from earliest-added items

lib/commands/cleanJobsInSet-3.lua

@@ -36,8 +36,12 @@ local rangeEnd = -1
 
 -- If we're only deleting _n_ items, avoid retrieving all items
 -- for faster performance
+--
+-- Start from the tail of the list, since that's where oldest elements
+-- are generally added for FIFO lists
 if limit > 0 then
-  rangeEnd = limit - 1
+  rangeStart = -1 - limit + 1
+  rangeEnd = -1
 end
 
 local jobIds = rcall(command, setKey, rangeStart, rangeEnd)
@@ -91,8 +95,8 @@ while ((limit <= 0 or deletedCount < limit) and next(jobIds, nil) ~= nil) do
 
   if deletedCount < limit then
     -- We didn't delete enough. Look for more to delete
-    rangeStart = rangeStart + limit
-    rangeEnd = rangeEnd + limit
+    rangeStart = rangeStart - limit
+    rangeEnd = rangeEnd - limit
     jobIds = rcall(command, setKey, rangeStart, rangeEnd)
   end
 end

test/test_queue.js

@@ -2853,6 +2853,18 @@ describe('Queue', () => {
       expect(len).to.be.eql(2);
     });
 
+    it('shouldn\'t clean anything if all jobs are in grace period', async () => {
+      await queue.add({ some: 'data' });
+      await queue.add({ some: 'data' });
+
+      const cleaned = await queue.clean(5000, 'wait', 1);
+      expect(cleaned.length).to.be.eql(0);
+
+      const cleaned2 = await queue.clean(5000, 'wait');
+      expect(cleaned2.length).to.be.eql(0);
+      expect(await queue.count()).to.be.eql(2);
+    });
+
     it('should properly clean jobs from the priority set', done => {
       const client = new redis(6379, '127.0.0.1', {});
       queue.add({ some: 'data' }, { priority: 5 });