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From "Ariel Weisberg (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (CASSANDRA-9602) EACH_QUORUM READ support needed
Date Tue, 06 Oct 2015 20:55:27 GMT

     [ https://issues.apache.org/jira/browse/CASSANDRA-9602?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Ariel Weisberg updated CASSANDRA-9602:
--------------------------------------
    Reviewer: Ariel Weisberg

> EACH_QUORUM READ support needed
> -------------------------------
>
>                 Key: CASSANDRA-9602
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-9602
>             Project: Cassandra
>          Issue Type: Sub-task
>            Reporter: Scott Guminy
>            Assignee: Carl Yeksigian
>              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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