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From aaron morton <aa...@thelastpickle.com>
Subject Re: what happen if coordinator node fails during write
Date Fri, 28 Jun 2013 04:51:57 GMT
> As far as I know in 1.2 coordinator logs request before it updates replicas.
You may be thinking about atomic batches, which are enabled by default for 1.2 via CQL but
must be supported by Thrift clients. I would guess Hector is not using them. 
These logs are stored on other machines, which then reply the mutation if they have not been
removed by a certain time. 

> 
> I am writing data to Cassandra by thrift client (not hector) and
> wonder what happen if the coordinator node fails.

How and when it fails is important.
But lets say their was an OS level OOM situation and the process was killed just after it
sent messages to the remote replicas. In that case all you know if the request was applied
on 0 to RF number of replicas. So it's the same as a TimedOutException. 

The request did not complete at the request CL so reads to that data will be working eventual
consistency until the next successful write. 

Cheers


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

@aaronmorton
http://www.thelastpickle.com

On 26/06/2013, at 12:45 PM, Andrey Ilinykh <ailinykh@gmail.com> wrote:

> It depends on cassandra version. As far as I know in 1.2 coordinator logs request before
it updates replicas. If it fails it will replay log on startup.
> In 1.1 you may have inconsistant state, because only part of your request is propagated
to replicas.
> 
> Thank you,
>   Andrey
> 
> 
> On Tue, Jun 25, 2013 at 5:11 PM, Jiaan Zeng <jiaan@bloomreach.com> wrote:
> Hi there,
> 
> I am writing data to Cassandra by thrift client (not hector) and
> wonder what happen if the coordinator node fails. The same question
> applies for bulk loader which uses gossip protocol instead of thrift
> protocol. In my understanding, the HintedHandoff only takes care of
> the replica node fails.
> 
> Thanks.
> 
> --
> Regards,
> Jiaan
> 


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