I forgot to cc to riak-users.
---------- Forwarded message ----------
From: Tatsuya Kawano <t650...@gmail.com>
Date: 2012/9/27
Subject: Re: Reading with "r = all" always succeeds in Riak 1.2 even
when one of the primary nodes is down?
To: Evan Vigil-McClanahan <emcclana...@basho.com>
Thanks, Evan.
I tried pr=all and verified it failed as expected. I didn't know about
fallback vnode will actively repair objects (I think it's not
documented in Riak Wiki) but now I understand how it works.
- Tatsuya
2012/9/27 Evan Vigil-McClanahan <emcclana...@basho.com>:
> Hi Tatsuya,
>
> Once the fallback ('secondary') vnode has started on another node,
> r=all is going to work again. pr=all shouldn't, though.
>
> On Wed, Sep 26, 2012 at 2:51 PM, Tatsuya Kawano <t650...@gmail.com> wrote:
>> Hi,
>>
>> I'm having hard time to verify this behavior on the Riak wiki with my
>> Riak 1.2 test environment. Can anybody help me to figure out what is
>> happening?
>>
>>
>> http://wiki.basho.com/Eventual-Consistency.html#Failure-Scenarios
>>
>>> Reading When One Primary Fails
>>> ------------------------------
>>>
>>> 1. Data is written to a key with W=3
>>> 2. One node goes down, it happens to be a primary for that key
>>> 3. Data is read from that key with R=3
>>> 4. Riak returns not_found on first request
>>> 5. Read repair ensures data is replicated to a secondary node.
>>> Read repair will always occur, regardless of the R value.
>>> Even with an R of 2, read repair will kick in and ensure that
>>> all nodes responsible for this particular data are consistent.
>>> 6. Subsequent reads return correct value with R=3, two values
>>> coming from primary and one from secondary nodes
>>
>>
>> At the first read (step 4), Riak should return not_found, but it
>> actually retuns the correct value. I wonder when read repair will kick
>> in in Riak 1.2. (even before the first read?)
>>
>>
>> I followed the screencast "Tuning CAP Controls in Riak" on this page.
>> http://wiki.basho.com/Tunable-CAP-Controls-in-Riak.html
>>
>> I used riak_core_ring:preflist/2 to ensure that I had took down one of
>> the correct primary nodes for the key.
>>
>> Thanks,
>> Tatsuya
>>
>> --
>> Tatsuya Kawano (Mr.)
>> Tokyo, Japan
>>
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>> riak-users@lists.basho.com
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