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From aaron morton <aa...@thelastpickle.com>
Subject Re: re-execution of failed queries with rpc_timeout
Date Tue, 16 Apr 2013 21:08:13 GMT
If you are using Counters you need to do everything you can to avoid timeouts. In the worse
case we do not know where it has been applied. The increment is applied on a lead and then
replicated to the others, if the coordinator is not  the lead it may not know if the increments
was applied at all. 

Start by reducing the size of the updates. Larger batches do not always mean better performance.


>  In all other cases, the rpc_timeout might be thrown from a remote node (not the one
I'm connected to), and hence some parts of the update will be performed and others parts will
not.
TimedOutException is always thrown from the coordinator you are connected to. 

Cheers

-----------------
Aaron Morton
Freelance Cassandra Consultant
New Zealand

@aaronmorton
http://www.thelastpickle.com

On 15/04/2013, at 1:38 PM, Moty Kosharovsky <motykosh@gmail.com> wrote:

> Sorry, not LOCAL QUORUM, I meant "ANY" quorum.
> 
> 
> On Mon, Apr 15, 2013 at 4:12 AM, Moty Kosharovsky <motykosh@gmail.com> wrote:
> Hello,
> 
> I'm running a 12 node cluser with cassandra 1.1.5 and oracle jdk 1.6.0_35. Our application
constantly writes large updates with cql. Once in a while, an rpc_time will occur.
> 
> Since a lot of the information is counters, its impossible for me to understand if the
updates complete partially on rpc_timeout, or cassandra somehow rolls back the change completely,
and hence I can't tell if I should re-execute the query on rpc_timeout (with double processing
being a bigger concern than missing updates).
> 
> I am thinking, but unsure of this, that if I'll switch to LOCAL_QUORUM, rpc_timeout will
always mean that the update was not processes as a whole. In all other cases, the rpc_timeout
might be thrown from a remote node (not the one I'm connected to), and hence some parts of
the update will be performed and others parts will not.
> 
> Anyone solved this issue before?
> 
> Kind Regards,
> Kosha
> 


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