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From Ajay Garg <ajaygargn...@gmail.com>
Subject Re: Doubt regarding consistency-level in Cassandra-2.1.10
Date Wed, 04 Nov 2015 08:20:38 GMT
Hi All.

I think we got the root-cause.

One of the fields in one of the class was marked with "@Version"
annotation, which was causing the Cassandra-Java-Driver to insert "If Not
Exists" in the insert query, thus invoking SERIAL consistency-level.

We removed the annotation (didn't really need that), and we have not
observed the error since about an hour or so.


Thanks Eric and Bryan for the help !!!


Thanks and Regards,
Ajay

On Wed, Nov 4, 2015 at 8:51 AM, Ajay Garg <ajaygargnsit@gmail.com> wrote:

> Hmm... ok.
>
> Ideally, we require ::
>
> a)
> The intra-DC-node-syncing takes place at the statement/query level.
>
> b)
> The inter-DC-node-syncing takes place at cassandra level.
>
>
> That way, we don't spend too much delay at the statement/query level.
>
>
> For the so-called CAS/lightweight transactions, the above are impossible
> then?
>
> On Wed, Nov 4, 2015 at 5:58 AM, Bryan Cheng <bryan@blockcypher.com> wrote:
>
>> What Eric means is that SERIAL consistency is a special type of
>> consistency that is only invoked for a subset of operations: those that use
>> CAS/lightweight transactions, for example "IF NOT EXISTS" queries.
>>
>> The differences between CAS operations and standard operations are
>> significant and there are large repercussions for tunable consistency. The
>> amount of time such an operation takes is greatly increased as well; you
>> may need to increase your internal node-to-node timeouts .
>>
>> On Mon, Nov 2, 2015 at 8:01 PM, Ajay Garg <ajaygargnsit@gmail.com> wrote:
>>
>>> Hi Eric,
>>>
>>> I am sorry, but I don't understand.
>>>
>>> If there had been some issue in the configuration, then the
>>> consistency-issue would be seen everytime (I guess).
>>> As of now, the error is seen sometimes (probably 30% of times).
>>>
>>> On Mon, Nov 2, 2015 at 10:24 PM, Eric Stevens <mightye@gmail.com> wrote:
>>>
>>>> Serial consistency gets invoked at the protocol level when doing
>>>> lightweight transactions such as CAS operations.  If you're expecting that
>>>> your topology is RF=2, N=2, it seems like some keyspace has RF=3, and so
>>>> there aren't enough nodes available to satisfy serial consistency.
>>>>
>>>> See
>>>> http://docs.datastax.com/en/cassandra/2.0/cassandra/dml/dml_ltwt_transaction_c.html
>>>>
>>>> On Mon, Nov 2, 2015 at 1:29 AM Ajay Garg <ajaygargnsit@gmail.com>
>>>> wrote:
>>>>
>>>>> Hi All.
>>>>>
>>>>> I have a 2*2 Network-Topology Replication setup, and I run my
>>>>> application via DataStax-driver.
>>>>>
>>>>> I frequently get the errors of type ::
>>>>> *Cassandra timeout during write query at consistency SERIAL (3 replica
>>>>> were required but only 0 acknowledged the write)*
>>>>>
>>>>> I have already tried passing a "write-options with LOCAL_QUORUM
>>>>> consistency-level" in all create/save statements, but I still get this
>>>>> error.
>>>>>
>>>>> Does something else need to be changed in
>>>>> /etc/cassandra/cassandra.yaml too?
>>>>> Or may be some another place?
>>>>>
>>>>>
>>>>> --
>>>>> Regards,
>>>>> Ajay
>>>>>
>>>>
>>>
>>>
>>> --
>>> Regards,
>>> Ajay
>>>
>>
>>
>
>
> --
> Regards,
> Ajay
>



-- 
Regards,
Ajay

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