Hi, I am trying to understand hedwig. I tried reading the documentation user.txt, dev.txt along with the code but still some design aspects are not clear.
Can someone please tell the following: (Lets say there are 2 regions A and B) 1. When a subscriber X subscribes to topic T in region A, then does RegionManager automatically adds a subscription (with id = __A) to topic T in B. The RegionManager class has couple of callbacks and I was not able to understand it properly. 2. What happens when X and Y in region A subscribe to topic T. Does RegionManager tries to do separate subscription for X and Y in B? Since the RegionManager uses a static subscriber Id, the second subscription request will be considered duplicate. 3. How does X gets messages from region B? The RegionManager callbacks are bit confusing and I was not able to understand. 4. What is the purpose of org.apache.hedwig.server.proxy package classes (HedwigProxy etc.). There is no documentation to explain the same. 5. What happens when one of the hub dies. The publisher will try to contact another hub? But what about the subscribers? Do they need to do any error handling / recovery? 6. Hedwig architecture mandates the need for a load balancer. As per my understanding it is required because the zk instances of different regions is not shared. I would expect all hosts information to be maintained in zk, and even for cross colo, the information should be shared through zk (may be that requires SSL support in zk). -regards Amit
