Performance Modeling and Benchmarking of Event-Based ... - DVS

50 CHAPTER 4. PERFORMANCE ENGINEERING OF EVENT-BASED SYSTEMS
The Controller place is in state A which is represented by a State A token stored in the
depository.
After the system initialization, the following tokens exist in the system:
Place Color Count Note
Controller State A 1 Init value.
Controller Subscriber A n Received via T0.
2. Creation of Notifications
(a) Producer Publishes Event
The producer publishes an Event token, which arrives via T1 at the broker. After
the broker received the Event token, the transition T2-II is fired and changes the
state of the Controller from A to B by replacing the State A token with a State B
token.
Place Color Count Note
Controller State B 1 Produced by T2.
Controller Subscriber A n
(b) Notification of Subscribers
Since the Controller place is now state B, transition T2-IV is fired for each of the
n Subscriber A tokens and transforms them as illustrated in Figure 4.10(b) into
Notification tokens (sent to the Broker) and into Subscriber B tokens stored in the
Controller, respectively. These Notification tokens will be processed by the Broker
and afterwards delivered to the consumers. Therefore, each Event token triggers the
generation of n Notifications.
Place Color Count Note
Controller State B 1
Controller Subscriber B n
Broker Notification n To be forwarded to the consumer.
QPN Definition
Places:
Place Type Description
Producer S Publishes events.
Broker Q Receives all incoming events and forwards notifications to
the consumers.
Consumer S Consumes incoming events.
Controller O Controls the creation of Notification token.
Init O Central place for the configuration.
Note The Init place can be used to configure the number of subscribers of different
interactions.
Colors: