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https://issues.apache.org/jira/browse/CASSANDRA-9602?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Tyler Hobbs updated CASSANDRA-9602:
-----------------------------------
Labels: client-impacting doc-impacting (was: )
> EACH_QUORUM READ support needed
> -------------------------------
>
> Key: CASSANDRA-9602
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9602
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Scott Guminy
> Assignee: Tyler Hobbs
> Labels: client-impacting, doc-impacting
> Fix For: 3.x
>
>
> 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:
>
> # *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
> # *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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