add pagination to worker counts, preserves backwards compatibility

api.lua

@@ -74,8 +74,8 @@ QlessAPI.heartbeat = function(now, jid, worker, data)
   return Qless.job(jid):heartbeat(now, worker, data)
 end
 
-QlessAPI.workers = function(now, worker)
-  return cjson.encode(QlessWorker.counts(now, worker))
+QlessAPI.workers = function(now, ...)
+  return cjson.encode(QlessWorker.counts(now, unpack(arg)))
 end
 
 QlessAPI.track = function(now, command, jid)

test/test_worker.py

@@ -10,6 +10,12 @@ def setUp(self):
         # No grace period
         self.lua('config.set', 0, 'grace-period', 0)
 
+    def test_malformed(self):
+        '''Enumerate all the ways in which the input can be malformed'''
+        self.assertMalformed(self.lua, [
+            ('workers', 1, 0, 'arg2') # Count arg malformed
+        ])
+
     def test_basic(self):
         '''Basic worker-level information'''
         self.lua('put', 0, 'worker', 'queue', 'jid', 'klass', {}, 0)
@@ -24,6 +30,31 @@ def test_basic(self):
             'stalled': 0
         }])
 
+    def test_paginated(self):
+        '''Paginated worker-level information'''
+
+        self.lua('put', 0, 'worker-1', 'queue', 'jid-1', 'klass', {}, 0)
+        self.lua('pop', 1, 'queue', 'worker-1', 10)
+        self.lua('put', 2, 'worker-2', 'queue', 'jid-2', 'klass', {}, 0)
+        self.lua('pop', 3, 'queue', 'worker-2', 10)
+        self.lua('put', 2, 'worker-3', 'queue', 'jid-3', 'klass', {}, 0)
+        self.lua('pop', 3, 'queue', 'worker-3', 10)
+
+        worker_names = [w['name'] for w in self.lua('workers', 20)]
+        self.assertEqual(worker_names, ['worker-3', 'worker-2', 'worker-1'])
+
+        worker_names = [w['name'] for w in self.lua('workers', 20, 0, 1)]
+        self.assertEqual(worker_names, ['worker-3'])
+
+        worker_names = [w['name'] for w in self.lua('workers', 20, 1, 1)]
+        self.assertEqual(worker_names, ['worker-2'])
+
+        worker_names = [w['name'] for w in self.lua('workers', 20, 2, 1)]
+        self.assertEqual(worker_names, ['worker-1'])
+
+        worker_names = [w['name'] for w in self.lua('workers', 20, 1, 2)]
+        self.assertEqual(worker_names, ['worker-2', 'worker-1'])
+
     def test_stalled(self):
         '''We should be able to detect stalled jobs'''
         self.lua('put', 0, 'worker', 'queue', 'jid', 'klass', {}, 0)

worker.lua

@@ -3,6 +3,8 @@ function QlessWorker.deregister(...)
   redis.call('zrem', 'ql:workers', unpack(arg))
 end
 
+-- Counts(now, [offset, [count]])
+-- Counts(now, worker)
 -- Provide data about all the workers, or if a specific worker is provided,
 -- then which jobs that worker is responsible for. If no worker is provided,
 -- expect a response of the form:
@@ -31,7 +33,7 @@ end
 --      ]
 --  }
 --
-function QlessWorker.counts(now, worker)
+function QlessWorker.counts(now, ...)
   -- Clean up all the workers' job lists if they're too old. This is
   -- determined by the `max-worker-age` configuration, defaulting to the
   -- last day. Seems like a 'reasonable' default
@@ -45,14 +47,26 @@ function QlessWorker.counts(now, worker)
   -- And now remove them from the list of known workers
   redis.call('zremrangebyscore', 'ql:workers', 0, now - interval)
 
+  --- Preserve backwards compatibility for counts() which only
+  --- takes a worker and not offset/count
+  local worker
+  if not tonumber(arg[1]) then
+    worker = arg[1]
+  end
+
   if worker then
     return {
       jobs    = redis.call('zrevrangebyscore', 'ql:w:' .. worker .. ':jobs', now + 8640000, now),
       stalled = redis.call('zrevrangebyscore', 'ql:w:' .. worker .. ':jobs', now, 0)
     }
   else
+    local offset = assert(tonumber(arg[1] or 0),
+      'Failed(): Arg "offset" is not a number: ' .. tostring(arg[1]))
+    local count = assert(tonumber(arg[2] or 0),
+      'Failed(): Arg "count" is not a number: ' .. tostring(arg[2]))
+
     local response = {}
-    local workers = redis.call('zrevrange', 'ql:workers', 0, -1)
+    local workers = redis.call('zrevrange', 'ql:workers', offset, offset + count - 1)
     for index, worker in ipairs(workers) do
       table.insert(response, {
         name    = worker,