[jira] [Created] (BOOKKEEPER-606) Scale Subscriptions

["Jiannan Wang (JIRA)" <ji...@apache.org>]

Jiannan Wang created BOOKKEEPER-606:
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             Summary: Scale Subscriptions
                 Key: BOOKKEEPER-606
                 URL: https://issues.apache.org/jira/browse/BOOKKEEPER-606
             Project: Bookkeeper
          Issue Type: New Feature
          Components: hedwig-client, hedwig-server
    Affects Versions: 4.2.1, 4.2.0
            Reporter: Jiannan Wang


At present, Hedwig is able to scale topic but not subscription, so one topic can only serve a few subscribers. However, there are many user cases with huge subscriptions in reality: lots of users are interested in same things, such as specific sport game, famous people's activity (update on twitter/facebook), etc.

And if Hedwig user plans to scale subscriptions, the only way I know is transform subscription into topic: for each subscription, create a new topic "topic#subId" then each topic consists of only one subscriber. It do resolve the scalability issue but it is not an ideal solution:
   * Topic amount grows a lot, which increases the metadata usage and demands more Hub servers.
   * Each message is replicated for each subscriber. In other words, assume there are S subscribers with M messages on the topic, then the actual message number in the system is S x M!

This JIRA aims to find a better solution for Hedwig to afford subscription scalability.

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