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The "HedWig" page has been changed by mahadevkonar. http://wiki.apache.org/hadoop/HedWig?action=diff&rev1=11&rev2=12 -------------------------------------------------- Now digging down into a region, it consists of a collection of '''hub servers'''. Hub servers aggregate messages published in a region and persist them. They also subscribe to hubs in other regions to listen for messages that their clients are subscribed to. Clients always subscribe only to local hub servers. Hedwig plans to use [[http://hadoop.apache.org/zookeeper/ | Zookeeper]] for persistence of metadata, and [[https://issues.apache.org/jira/browse/ZOOKEEPER-276 | Bookkeeper]] for persistence of actual messages. - {{attachment:region_1.png}} + {{attachment:region_1.jpg}} Topics are randomly split over hubs. When the hub responsible for a topic fails, another hub should take over responsibility of the topic. Now digging into a hub, it consists of 6 components: - {{attachment:hub.png}} + {{attachment:hub.jpg}} 1. '''Network-I/O component''': For high throughput, we use Java NIO through a framework called [[http://www.jboss.org/netty | Netty]]. 1. '''Topic Manager''': Maintains and coordinates ownership of topics among hubs. It is responsible for doing automatic failover when a hub dies. It will be a Zookeeper client.
