Hi Alex,
i have only One DC (with name DC1) and have only one keyspace. So i dont
think so both of the scenario is possible. (yes in my case QUORUM is
equivalent
of ALL)
cqlsh> SELECT * FROM system_schema.keyspaces where keyspace_name='adlog' ;
keyspace_name | durable_writes | replication
---------------+----------------+-------------------------------------------------------------------------------
adlog | True | {'DC1': '2', 'class':
'org.apache.cassandra.locator.NetworkTopologyStrategy'}
On Tue, Feb 27, 2018 at 2:27 PM, Oleksandr Shulgin <
[email protected]> wrote:
> On Tue, Feb 27, 2018 at 9:45 AM, Abhishek Kumar Maheshwari <
> [email protected]> wrote:
>
>>
>> i have a KeySpace in Cassandra (cassandra version 3.0.9- total 12 Servers
>> )With below definition:
>>
>> {'DC1': '2', 'class': 'org.apache.cassandra.locator.
>> NetworkTopologyStrategy'}
>>
>> Some time i am getting below exception
>>
>> [snip]
>
>> Caused by: com.datastax.driver.core.exceptions.WriteTimeoutException:
>> Cassandra timeout during write query at consistency QUORUM (3 replica were
>> required but only 2 acknowledged the write)
>> at com.datastax.driver.core.exceptions.WriteTimeoutException.co
>> py(WriteTimeoutException.java:100)
>> at com.datastax.driver.core.Responses$Error.asException(Respons
>> es.java:134)
>> at com.datastax.driver.core.RequestHandler$SpeculativeExecution
>> .onSet(RequestHandler.java:525)
>> at com.datastax.driver.core.Connection$Dispatcher.channelRead0(
>> Connection.java:1077)
>>
>> why its waiting for acknowledged from 3rd server as replication factor
>> is 2?
>>
>
> I see two possibilities:
>
> 1) The data in this keyspace is replicated to another DC, so there is also
> 'DC2': '2', for example, but you didn't show it. In this case QUORUM
> requires more than 2 nodes.
> 2) The write was targeting a table in a different keyspace than you think.
>
> In any case QUORUM (or LOCAL_QUORUM) with RF=2 is equivalent of ALL. Not
> sure why would you use it in the first place.
>
> For consistency levels involving quorum you want to go with RF=3 in a
> single DC. For multi DC you should think if you want QUORUM or EACH_QUORUM
> for your writes and figure out the RFs from that.
>
> Cheers,
> --
> Alex
>
>
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