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  1. Cassandra
  2. CASSANDRA-9602

EACH_QUORUM READ support needed

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      EACH_QUORUM consistency for READ should be added.

      This bug https://issues.apache.org/jira/browse/CASSANDRA-3272 says it is not needed ever, however I have a use case where I need it. I think the decision made was incorrect. Here's why...

      My application has two key pieces:

      1. End user actions which add/modify data in the system. End users typically access the application from only one Data Center and only see their own data
      2. Scheduled business logic tasks which run from any node in any data center. These tasks process data added by the end users in an asynchronous way

      End user actions must have the highest degree of availability. Users must always be able to add data to the system. The data will be processed later. To support this, end user actions will use LOCAL_QUORUM Read and Write Consistency.

      Scheduled tasks don't need to have a high degree of availability but MUST operate on the most up to date data. The tasks will run with EACH_QUORUM to ensure that no matter how many data centers we have, we always READ the latest data. This approach allows us some amount of fault tolerance.

      The problem is that EACH_QUORUM is not a valid READ consistency level. This mean I have no alternative but to use ALL. ALL will work, but is not the best since it offers support for ZERO failures. I would prefer EACH_QUORUM since it can support some failures in each data center.

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              carlyeks Carl Yeksigian
              guminy Scott Guminy
              Carl Yeksigian
              Ariel Weisberg
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