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From Tamar Fraenkel <ta...@tok-media.com>
Subject Re: consistency level question
Date Sun, 18 Mar 2012 07:38:10 GMT
Hi!
Thanks for the prompt answer,
That is true, I intend to have it at two.
What you say, is that if I change that, then even when the node is down, my
application will be able to read\write from the other node where the data
is replicated?

Forgot to mention that I have
        ConfigurableConsistencyLevel ccl = new
ConfigurableConsistencyLevel();
        ccl.setDefaultReadConsistencyLevel(HConsistencyLevel.ONE);
        ccl.setDefaultWriteConsistencyLevel(HConsistencyLevel.ONE);
        keyspace = HFactory.createKeyspace(KEYSPACE, cluster, ccl,
                new FailoverPolicy(3, 10));

Thanks,

*Tamar Fraenkel *
Senior Software Engineer, TOK Media

[image: Inline image 1]

tamar@tok-media.com
Tel:   +972 2 6409736
Mob:  +972 54 8356490
Fax:   +972 2 5612956





On Sun, Mar 18, 2012 at 9:31 AM, Caleb Rackliffe <caleb@steelhouse.com>wrote:

> If your replication factor is set to one, your cluster is obviously in a
> bad state following any node failure.  At best, I think it would make sense
> that about a third of your operations fail, but I'm not sure why all of
> them would.  I don't know if Hector just refuses to work with a compromised
> cluster, etc.
>
> I guess I'm wondering why your replication factor is set to 1…
>
> *
> Caleb Rackliffe | Software Developer
> M 949.981.0159 | caleb@steelhouse.com
> **
>  *
>
> From: Tamar Fraenkel <tamar@tok-media.com>
> Reply-To: "user@cassandra.apache.org" <user@cassandra.apache.org>
> Date: Sun, 18 Mar 2012 03:15:53 -0400
> To: "cassandra-user@incubator.apache.org" <
> cassandra-user@incubator.apache.org>
> Subject: consistency level question
>
> Hi!
> I have a 3 node cassandra cluster.
> I use Hector API.
>
> I give hecotr one of the node's IP address
> I call setAutoDiscoverHosts(true) and setRunAutoDiscoveryAtStartup(true).
>
> The describe on one node returns:
>
> Replication Strategy: org.apache.cassandra.locator.SimpleStrategy
>   Durable Writes: true
>     Options: [replication_factor:1]
>
> The odd thing is that when I take one of the nodes down, expecting all to
> continue running smoothly, I get exceptions of the format seen bellow, and
> no read or write succeeds. When I bring the node back up, exceptions stop
> and read and write resumes.
>
> Any idea or explanation why this is the case?
> Thanks!
>
>
> me.prettyprint.hector.api.exceptions.HUnavailableException: : May not be
> enough replicas present to handle consistency level.
>         at
> me.prettyprint.cassandra.service.ExceptionsTranslatorImpl.translate(ExceptionsTranslatorImpl.java:66)
>         at
> me.prettyprint.cassandra.service.KeyspaceServiceImpl$7.execute(KeyspaceServiceImpl.java:285)
>         at
> me.prettyprint.cassandra.service.KeyspaceServiceImpl$7.execute(KeyspaceServiceImpl.java:268)
>         at
> me.prettyprint.cassandra.service.Operation.executeAndSetResult(Operation.java:103)
>         at
> me.prettyprint.cassandra.connection.HConnectionManager.operateWithFailover(HConnectionManager.java:246)
>         at
> me.prettyprint.cassandra.service.KeyspaceServiceImpl.operateWithFailover(KeyspaceServiceImpl.java:131)
>         at
> me.prettyprint.cassandra.service.KeyspaceServiceImpl.getSlice(KeyspaceServiceImpl.java:289)
>         at
> me.prettyprint.cassandra.model.thrift.ThriftSliceQuery$1.doInKeyspace(ThriftSliceQuery.java:53)
>         at
> me.prettyprint.cassandra.model.thrift.ThriftSliceQuery$1.doInKeyspace(ThriftSliceQuery.java:49)
>         at
> me.prettyprint.cassandra.model.KeyspaceOperationCallback.doInKeyspaceAndMeasure(KeyspaceOperationCallback.java:20)
>         at
> me.prettyprint.cassandra.model.ExecutingKeyspace.doExecute(ExecutingKeyspace.java:85)
>         at
> me.prettyprint.cassandra.model.thrift.ThriftSliceQuery.execute(ThriftSliceQuery.java:48)
>         at
> me.prettyprint.cassandra.service.ColumnSliceIterator.hasNext(ColumnSliceIterator.java:60)
>         at
>
>
> *Tamar Fraenkel *
> Senior Software Engineer, TOK Media
>
> [image: Inline image 1]
>
> tamar@tok-media.com
> Tel:   +972 2 6409736
> Mob:  +972 54 8356490
> Fax:   +972 2 5612956
>
>
>
>

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