Fabric Controller is a significant part of Windows Azure architecture
Fabrics are group of machines in Microsoft’s datacenter which are
aggregated by a switch. The group of these machines is called cluster. Each cluster is
managed and owned by a fabric controller. They are replicated along with these machines.
It manages everything inside those machines, for e.g., load balancers, switches, etc. Each
machine has a fabric agent running inside it and fabric controller can communicate with
each fabric agent.
Imagine a situation where four instances of web role are running, and one of them dies.
The fabric controller will initiate a new instance to replace the dead one immediately.
Similarly, in case any virtual machine fails, a new one is assigned by the fabric controller.
It also resets the load balancers after assigning the new machine, so that it points to the
new machine instantaneously. Thus, all the intelligent tasks are performed by the Fabric
Controller in Windows Azure architecture.