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From Craig Ching <craigch...@gmail.com>
Subject Does Cassandra fit my requirements?
Date Thu, 14 Oct 2010 19:45:57 GMT
Hi!

I've been reading the wiki and some posts to this mailing list and writing
some tests to discover if Cassandra can be made to fit my needs.

For the most part, things are looking good.  However, I have one issue that
I am currently having problems with and it's making me think that maybe
Cassandra isn't a good fit for my needs.  For some of my larger users,
having a cluster of cassandra nodes that need to be separately maintained
might not be a huge issue.  However, for some smaller users, having to have
a separately maintained cassandra cluster will be too much of a management
headache.

For those users, what I was thinking I could do is run an embedded cassandra
node in our application in replicated mode.  So, there are two problems that
I'm seeing with this:

1.  Embedding doesn't seem to be a normal use-case for people (at least
that's the impression I got from the wiki in the section on embedding).
 This probably isn't a huge issue, I could just install a cassandra node
along with our application, but I'd like to hear more if people think
embedding is a good idea or what problems I might run into if I do choose to
embed.

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.

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 ;-)

Cheers,
Craig

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