title: Why Azure function been triggered by Event Grid about every 2 munites
body: <p>I am learning Azure Service Bus and Functinos.
  I have created a Service Bus namespace, a topic under the namespace and a subscription to the topic.</p>
  
  <p>Then I bind the Event Grid of the Service Bus namespace to the EndPoint of an Azure function to process the SB messages.</p>
  
  <p>When I sent several messages to the Service Bus topic, I can see from the "Monitor" of the Azure function, it was triggered about every 2 munites. The function does nothing but output the message, won't take long. 
  I expected the function to be triggered whenever there is a messages sent to the topic, but seems not, why it is like this?</p>
  
  <p>BTW, if I want to keep the Azure function to receive and process message one by one(Not in a parallel), how can I config it?</p>
  
  <p>Thanks</p>