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From Craig Ching <>
Subject Re: Does Cassandra fit my requirements?
Date Thu, 21 Oct 2010 14:30:15 GMT
Hi Peter, thanks for the response!  I appreciate your validation of our
needs.  Sorry it's taken me so long to get back, I've been knocked on my ass
with a nasty cold since late last week.

On Sat, Oct 16, 2010 at 7:37 AM, Peter Schuller <
> wrote:

> > 2.  What we really want for small users is just a replicated data store
> with
> > some caching.  Each of our application instances would have all the data
> > available to it.  If one application instance goes down, the other nodes
> > should continue to function just fine.
> Sounds reasonable, but make sure your application logic is okay to
> handle concurrent requests to multiple nodes for the same data. I.e.,
> that there is no problem associated with your application not having
> the only authoritative view of the data in-memory.
Yeah, understood, I think we're ok with that, we won't have a lot of writes
of data, we're more read-centric which concerns me a bit hearing that
Cassandra is more write-centric.  But we do have a need to store large
amounts of data, so I think Cassandra is right for us based on that.

> > So, with number 2, I've run into a situation that I don't think is going
> to
> > work for me, but hopefully I'm just missing something.  To test 2., I
> > installed a 2 node cluster.  On node A, I ran some code to populate one
> of
> > the nodes.  On both A and B, I can get data.  Now, I shutdown node A and
> > request data from Node B, I get a timed out exception from hector.  If I
> > leave A running, but shutdown B, I get an IllegalStateException:
> replication
> > factor (2) exceeds number of endpoints (1).  I have set my
> > replication_factor to 2.
> > Can I do what I want with Cassandra?  I appreciate any advice!  And I
> > apologize in advance if I've missed something obvious, I have all of
> about
> > 1.5 days experience and I'm trying to learn fast ;-)
> Does both A and B agree about the ring state (i.e., they both know
> about both nodes) prior to you shutting one of them down?
Actually, I figured out the problem on Friday night (sort of).  My problem
was either a bug in Hector (which I think is more likely at this point) or a
misunderstanding of Hector on my part.  It seems Hector wasn't taking my
ConsistencyLevelPolicy (or whatever it's called in Hector).  I switched to
Pelops and things were working much more as I thought they should.  So it
does appear that Cassandra will do what I need thus far.

> --
> / Peter Schuller

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