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From Sergey Naumov <sknau...@gmail.com>
Subject Re: how to access data only on specific node
Date Wed, 15 May 2013 06:51:33 GMT
see that RR works, but sometimes number of records have been read degrades.

RR is enabled on a random 10% of requests, see the read_repair_chance
setting for the CF.

OK, but I forgot to mention the main thing - each node in my config is a
standalone datacenter and distribution is DC1:1, DC2:1, DC3:1. So when I
try to read 1000 records with consistency ONE multiple times while
connected to node that just have been turned on, I got the following count
of records read (approximately): 120 220 310 390 .... 950 960 965 !! 955 !!
970 ... If all other nodes contain 1000 records and read repair already
delivered 965 records to local DC (and so - local node), why sometimes I
see degradation of total records read?



2013/5/15 aaron morton <aaron@thelastpickle.com>

> see that RR works, but sometimes number of records have been read
> degrades.
>
> RR is enabled on a random 10% of requests, see the read_repair_chance
> setting for the CF.
>
>  If so, then the question is: how to perform local reads to examine
> content of specific node?
>
> You can check which nodes are replicas for a key using
> nodetool getendpoints
>
> If you want to read all the rows for a particular row you need to use a
> range scan and limit it by the token ranges assigned to the node.
>
> Cheers
>
> -----------------
> Aaron Morton
> Freelance Cassandra Consultant
> New Zealand
>
> @aaronmorton
> http://www.thelastpickle.com
>
> On 14/05/2013, at 10:29 PM, Sergey Naumov <sknaumov@gmail.com> wrote:
>
> Hello.
>
> I'am playing with demo cassandra cluster and decided to test read repair +
> hinted handoff.
>
> One node of a cluster was put down deliberately, and on the other nodes I
> inserted some records (say 1000). HH is off on all nodes.
> Then I turned on the node, connected to it with cql (locally, so to
> localhost) and performed 1000 reads by row key (with consistency ONE). I
> see that RR works, but sometimes number of records have been read degrades.
> Is it because consistency ONE and local reads is not the same thing? If so,
> then the question is: how to perform local reads to examine content of
> specific node?
>
> Thanks in advance,
> Sergey Naumov.
>
>
>

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