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From Nate McCall <n...@datastax.com>
Subject Re: HUnavailableException: : May not be enough replicas present to handle consistency level.
Date Fri, 02 Sep 2011 20:44:01 GMT
In your options, you have configured 2 replicas for each data center:
Options: [DC2:2, DC1:2]

If one of those replicas is down, then LOCAL_QUORUM will fail as there
is only one replica left 'locally.'


On Fri, Sep 2, 2011 at 3:35 PM, Oleg Tsvinev <oleg.tsvinev@gmail.com> wrote:
> from http://www.datastax.com/docs/0.8/consistency/index:
>
> <A “quorum” of replicas is essentially a majority of replicas, or RF /
> 2 + 1 with any resulting fractions rounded down.>
>
> I have RF=2, so majority of replicas is 2/2+1=2 which I have after 3rd
> node goes down?
>
> On Fri, Sep 2, 2011 at 1:22 PM, Nate McCall <nate@datastax.com> wrote:
>> It looks like you only have 2 replicas configured in each data center?
>>
>> If so, LOCAL_QUORUM cannot be achieved with a host down same as with
>> QUORUM on RF=2 in a single DC cluster.
>>
>> On Fri, Sep 2, 2011 at 1:40 PM, Oleg Tsvinev <oleg.tsvinev@gmail.com> wrote:
>>> I believe I don't quite understand semantics of this exception:
>>>
>>> me.prettyprint.hector.api.exceptions.HUnavailableException: : May not
>>> be enough replicas present to handle consistency level.
>>>
>>> Does it mean there *might be* enough?
>>> Does it mean there *is not* enough?
>>>
>>> My case is as following - I have 3 nodes with keyspaces configured as following:
>>>
>>> Replication Strategy: org.apache.cassandra.locator.NetworkTopologyStrategy
>>> Durable Writes: true
>>> Options: [DC2:2, DC1:2]
>>>
>>> Hector can only connect to nodes in DC1 and configured to neither see
>>> nor connect to nodes in DC2. This is for replication by Cassandra
>>> means, asynchronously between datacenters DC1 and DC2. Each of 6 total
>>> nodes can see any of the remaining 5.
>>>
>>> and inserts with LOCAL_QUORUM CL work fine when all 3 nodes are up.
>>> However, this morning one node went down and I started seeing the
>>> HUnavailableException: : May not be enough replicas present to handle
>>> consistency level.
>>>
>>> I believed if I have 3 nodes and one goes down, two remaining nodes
>>> are sufficient for my configuration.
>>>
>>> Please help me to understand what's going on.
>>>
>>
>

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