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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Update of "HedWig" by mahadevkonar
Date Wed, 17 Nov 2010 23:07:30 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Hadoop Wiki" for change notification.

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.

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