Amazon Interview Question
Design a "Subscriber - Broker - Publisher" architecture (a) running on a machine; (b) running on a cluster. Write the code for the 3 classes. Details: there are Events, specified by an "event type" and a blob of detailed info. Each subscriber subscribes with a Broker for a certain event type that it wants to get. Subscribers send events to the broker, and the relevant subscribers need to be notified.
Interview Answer
Anonymous
The observer and observable design pattern can come in handy here. Or if you wanted to do it without the interfaces, simply maintain a list of all publishers in the broker and a map of which subscibers can be attributed to a particular publisher. then whenever there is an event from the publisher, simply notify all the subcribers for that publisher.