so my environment is set in cloud service with 2 instances of worker role which process messages from service bus queue.I have also set up autoscaling block to increase instances when an instance has more than 10 messages to handle. here are steps i take. I push messages to a queue about 1000 current all my messages are unprocessed as my instances are not up. i publish the worker role with 2 instances, and when they are up,they start reading messages correctly. then i configure autoscaling in above stated rule for queues and 10 messages per instance.
What I excpected was since the instances already have more than they can handle, azure should start spinning up new instance.but this doesnt happen untill at least 10-15 minutes after my first two instances are up.
What could be the reason behind this and any algorithm on microsoft side?