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From Oleg Tsvinev <oleg.tsvi...@gmail.com>
Subject Re: HUnavailableException: : May not be enough replicas present to handle consistency level.
Date Fri, 02 Sep 2011 20:51:22 GMT
Do you mean I need to configure 3 replicas in each DC and keep using
LOCAL_QUORUM? In which case, if I'm following your logic, even one of
the 3 goes down I'll still have 2 to ensure LOCAL_QUORUM succeeds?

On Fri, Sep 2, 2011 at 1:44 PM, Nate McCall <nate@datastax.com> wrote:
> 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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