[GitHub] [accumulo] keith-turner opened a new pull request #1174: fix #816 abstract metadata and change root metadata schema

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keith-turner opened a new pull request #1174: fix #816 abstract metadata and change root metadata schema
URL: https://github.com/apache/accumulo/pull/1174
 
 
   There are three major changes in this commit :
   
    * An abstraction layer for interacting with Accumulo's persisted
      metadata called Ample was introduced.  The goal is to eventually make
      all metadata read and write operations use Ample.
    * How the root tablet's metadata is stored in zookeeper was changed. It
      was changed to use a single zookeeper node (which is good for making
      atomic updates to multiple fields). In this single zookeeper node a
      json value is stored.  This json value has the same schema as all
      other metadata tablets, it uses the same column families and
      qualifiers.  This makes updating the json using Accumulo mutations
      easy and reading the json as Accumulo Key values easy.
    * Alot of the root tablet code that used to interact directly with
      Zookeeper was updated to use Ample.  In follow on changes, a lot of
      specialized root tablet code can be completely removed.  Those
      changes were not made in this commit inorder to keep it from
      becoming too large, making it hard to review.
   
   This change is starting point to support many other changes like #816,

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