move tasks to the end when queued

lib/cylc/task_pool.py

@@ -569,25 +569,30 @@ def get_ready_tasks(self):
         Return the tasks that are dequeued.
         """
 
-        # 1) queue unqueued tasks that are ready to run or manually forced
         now = time()
-        for itask in self.get_tasks():
-            if itask.state.status != TASK_STATUS_QUEUED:
-                # only need to check that unqueued tasks are ready
-                if itask.manual_trigger or itask.ready_to_run(now):
-                    # queue the task
-                    itask.state.reset_state(TASK_STATUS_QUEUED)
-                    itask.reset_manual_trigger()
-
-        # 2) submit queued tasks if manually forced or not queue-limited
         ready_tasks = []
         qconfig = self.config.cfg['scheduling']['queues']
+
         for queue in self.queues:
-            # 2.1) count active tasks and compare to queue limit
             n_active = 0
             n_release = 0
             n_limit = qconfig[queue]['limit']
             tasks = self.queues[queue].values()
+
+            # 1) queue unqueued tasks that are ready to run or manually forced
+            for itask in tasks:
+                if itask.state.status != TASK_STATUS_QUEUED:
+                    # only need to check that unqueued tasks are ready
+                    if itask.manual_trigger or itask.ready_to_run(now):
+                        # queue the task
+                        itask.state.reset_state(TASK_STATUS_QUEUED)
+                        itask.reset_manual_trigger()
+                        # move the task to the back of the queue
+                        self.queues[queue][itask.identity] = \
+                            self.queues[queue].pop(itask.identity)
+
+            # 2) submit queued tasks if manually forced or not queue-limited
+            # 2.1) count active tasks and compare to queue limit
             if n_limit:
                 for itask in tasks:
                     if itask.state.status in [TASK_STATUS_READY,