node,vm_tasks: added check_queue() method to get_remore_queue_name

This call can inspect wather the queue has active worker waiting for
tasks.

circle/vm/models/node.py

@@ -94,8 +94,16 @@ class Node(TimeStampedModel):
         """
         return self.ram_size * self.overcommit
 
+    @method_cache(30)
     def get_remote_queue_name(self, queue_id):
-        return self.host.hostname + "." + queue_id
+        """ Return the remote queue name
+        throws Exception if there is no worker on the queue.
+        Until the cache provide reult there can be dead quques.
+        """
+        if vm_tasks.check_queue(self.host.hostname, queue_id):
+            return self.host.hostname + "." + queue_id
+        else:
+            raise Exception("Worker not found.")
 
     def remote_query(self, task, timeout=30, raise_=False, default=None):
         """Query the given task, and get the result.

circle/vm/tasks/vm_tasks.py

 from manager.mancelery import celery
 
 
+def check_queue(node_hostname, queue_id):
+    drivers = ['vmdriver', 'netdriver']
+    worker_list = [node_hostname + "." + d for d in drivers]
+    queue_name = node_hostname + "." + queue_id
+    inspect = celery.control.inspect(worker_list)
+    # v is List of List of queues dict
+    node_workers = [v for k, v in inspect.active_queues().iteritems()]
+    for worker in node_workers:
+        for queue in worker:
+            if queue['name'] == queue_name:
+                return True
+    return False
+
+
 @celery.task(name='vmdriver.create')
 def deploy(params):
     pass