Communication between data-centers

[Rene Kochen <re...@schange.com>]

Hi all,

I have a question about communication between two data-centers, both with
replication-factor three.

If I read data using local_quorum from datacenter1, I see that digest
requests are sent to datacenter2. This is for read-repair I guess. How can
I prevent this from happening? Setting read_repair_chance does not help,
since it is ignored when using local_quorum.

In general, is read-repair between data-centers a performance issue when
doing a lot of local reads with local_quorum?

Thanks!

Rene

Re: Communication between data-centers

[Robert Coli <rc...@eventbrite.com>]

On Thu, Aug 14, 2014 at 9:24 AM, Rene Kochen <re...@emea.schange.com>
wrote:

> I am using 1.0.11, so I only have read_repair_chance.
>

I'm sure this goes without saying, but you should upgrade to the head of
1.2.x (probably via 1.1.x) ASAP. I would not want to operate 1.0.11 in
production in 2014.

=Rob

Re: Communication between data-centers

[Rene Kochen <re...@emea.schange.com>]

I am using 1.0.11, so I only have read_repair_chance.

However, after testing I see that read_repair_chance does work for
local_quorum.

Based on this site:
http://www.datastax.com/documentation/cassandra/2.0/cassandra/architecture/architectureClientRequestsRead_c.html
I got the impression that read_repair_chance only applies to consistency
level ONE.

However, when I test with local_quorum, I see that the read_repair_chance
is honored. In my test, there are two data-centers of three nodes each and
RF = 3 for both data-centers. Read-repair chance is set to 0.1

>From the logging I see that read-repair is most of the times not triggered.

Blockfor/repair is 2/false; setting up requests to /10.80.88.143,/
10.81.129.87 -> most cases
Blockfor/repair is 2/true; setting up requests to /10.80.88.143,/
10.81.129.87,/10.80.59.90,/10.80.30.12,/10.50.85.77,/10.80.19.244

Thanks!

Rene


2014-08-14 17:31 GMT+02:00 DuyHai Doan <do...@gmail.com>:

> dclocal_read_repair_chance option on the table is your friend
>
>
> http://www.datastax.com/documentation/cassandra/2.0/cassandra/reference/referenceTableAttributes.html?scroll=reference_ds_zyq_zmz_1k__dclocal_read_repair_chance
>
>
> On Thu, Aug 14, 2014 at 4:53 PM, Rene Kochen <re...@schange.com>
> wrote:
>
>> Hi all,
>>
>> I have a question about communication between two data-centers, both with
>> replication-factor three.
>>
>> If I read data using local_quorum from datacenter1, I see that digest
>> requests are sent to datacenter2. This is for read-repair I guess. How can
>> I prevent this from happening? Setting read_repair_chance does not help,
>> since it is ignored when using local_quorum.
>>
>> In general, is read-repair between data-centers a performance issue when
>> doing a lot of local reads with local_quorum?
>>
>> Thanks!
>>
>> Rene
>>
>
>

Re: Communication between data-centers

[DuyHai Doan <do...@gmail.com>]

dclocal_read_repair_chance option on the table is your friend

http://www.datastax.com/documentation/cassandra/2.0/cassandra/reference/referenceTableAttributes.html?scroll=reference_ds_zyq_zmz_1k__dclocal_read_repair_chance


On Thu, Aug 14, 2014 at 4:53 PM, Rene Kochen <re...@schange.com>
wrote:

> Hi all,
>
> I have a question about communication between two data-centers, both with
> replication-factor three.
>
> If I read data using local_quorum from datacenter1, I see that digest
> requests are sent to datacenter2. This is for read-repair I guess. How can
> I prevent this from happening? Setting read_repair_chance does not help,
> since it is ignored when using local_quorum.
>
> In general, is read-repair between data-centers a performance issue when
> doing a lot of local reads with local_quorum?
>
> Thanks!
>
> Rene
>