Available in the May CTP but release today on the 9th of August, an update of the AppFabric Service Bus containing the wonderful Queueus and Topics.
How to implement the great pub/sub mechanism by using Topics. Topics enable us to implement a 1-to-many messaging solution where the rules of filtering are NOT in your application (or database or whatsoever) but just like ACS, configuration on the Service Bus. It enables you to abstract messaging logic from your app to the bus instead of implementing complex rules in your application logic.
Imagine your application running on Azure (a workerrole) that is being diagnosed by using Performance Counters. These are collected locally and flushed to storage every configurable period. Now imagine your system administrators, responsible for monitoring your cloud assets, being at home but still need to be notified on events. Imagine 2 system administrators both having WP7 being the subscribers to your messaging solution. The first admin is responsible for scaling up and down your Windows Azure App (a workerrole doing lots of calculations) while the second system admin (who is the manager) is only to be notified on the actual scaling up and scaling down events. The first system admin will receive messages showing him averages of CPU utilization and free memory per hour. Based on this, he can decide to scale up or down. The example in the next blogpost below show how to setup the Service Bus and how to create this pub/sub mechanism.
I'll finish the next one in a few days.