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From "Sukant Hajra" <>
Subject Re: Read/Write Invariants Questions
Date Wed, 16 May 2012 20:32:11 GMT
Excerpts from Keith Turner's message of Wed May 16 02:42:17 -0500 2012:
> After a call to flush() on a batchwriter returns, any mutations
> written before the call to flush should be immediately visible.

I don't want to belabor the point, but I just want to be sure I'm not
interpreting your response too casually.  From your response, I'm now under the
impression that a flush blocks until the server sends back an acknowledgment
that the mutation has been written to the log.  Then all subsequent reads look
not only at HDFS, but also the write logs to make sure they have the most
consistent view?  Is this the case?  I appreciate the confirmation to save me a
dig into the source code.

If the reads are truly immediately consistent, has there ever been talk of
making inconsistent reads for the sake of improving read times?  Or is it all
in the noise with respect to network speeds and not worth the effort?

Also, if flush blocks waiting for an acknowledgment, I'm assuming that the
writer will throw a MutationsRejectedException.  If this happens, is the
BatchWriter still usable?  Or should I close it out and get a new one?  The
connector should be fine, though, right?  I'm just trying to make sure I have
my error handling logic sanely configured.

Other than that, thanks a lot for your prompt responses.  They really helped.


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