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From "Sukant Hajra" <qn2b6c2...@snkmail.com>
Subject Read/Write Invariants Questions
Date Wed, 16 May 2012 04:15:39 GMT
Hi,

There's a couple of sanity checks I wanted to run by the list:

    1. I see in the documentation that mutations may be partially read unless
    using IsolatedScanners, which is a way to have atomicity for applications.
    Is there any other mechanism for atomic operations to know about?

    2. I'm assuming that a flushed write to a row is not guaranteed to be
    sensed by a subsequent read (no immediate consistency).  Is this correct?

    3. When using a BatchWriter does the order in which mutations are added
    make any reliable assertion on the order that these mutations are sensed by
    subsequent reads?  Given two mutations A and B, I'd like to assert that any
    node sensing B will also sense A.

    4. I'm going to have a long standing thread doing batch writing.  Is it
    reasonable/safe to give this thread an open BatchWriter (making sure to
    close the writer when shutting down the thread)?  Or might this cause a
    memory leak?

    5. I'm assuming that BatchWriter is minimally blocking.  Is there any merit
    to or precedent of load balancing across multiple writers?  Or would that
    be redundant to optimizations already built into BatchWriter?

Thanks a lot for helping me better understand Accumulo.  Feel free to point me
to documentation I might have missed.

-Sukant

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