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Date: Thu, 29 Jul 2010 19:45:05 -0700
Message-ID: <AANLkTik9-q5ikkyQemtxvZiXzvSPKC_90zmvW0cciGeP@mail.gmail.com>
Subject: Re: cassandra 0.6.1 read returns wrong data?
From: Jianing Hu <jianing@gmail.com>
To: user@cassandra.apache.org
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That's an interesting thought. My code runs in FCGI and although the
cassandra connection is used to serve multiple requests, those
requests are supposedly processed sequentially, in a while
($request->Accept() >=3D 0) loop. However, we do call FCGI::finish to
close the request (so the HTTP request would finish) while continue
writing to cassandra. I wonder if that may cause the next request to
be accepted and trump the current one? I don't think it should but
it's worth testing.

Thanks,
- Jianing

On Thu, Jul 29, 2010 at 6:23 PM, Aaron Morton <aaron@thelastpickle.com> wro=
te:
> I was accidentally sharing connections between threads, and getting stran=
ge
> results. Is your client multi threaded?
>
> Can you provide some more information, such as the client library, how th=
e
> data is written and=A0 how you're deciding that the returned results are =
the
> wrong ones.
>
> Is the read inconsistency against data that is frequently changing? Could=
 it
> be a problem with the way the data is being stored?
>
> Aaron
>
>
>
>
> On 30 Jul, 2010,at 11:43 AM, Jianing Hu <jianing@gmail.com> wrote:
>
> Hi Aaron,
>
> Thanks for the reply. Can you explain what you mean by "sharing
> connections around"?
>
> I'm just calling a simple "get", and the data returned is for a
> completely different key. It's intermittent and hard to produce in my
> test environment, but can be observed in our production environment
> couple hundred times a day.
>
> Thanks,
> - Jianing
>
> On Thu, Jul 29, 2010 at 2:58 PM, Aaron Morton <aaron@thelastpickle.com>
> wrote:
>> I noticed this once when accidentally sharing connections around. Could
>> that
>> be the case ?
>>
>> What sort of commands are you running ? Could you be seeing this problem=
 ?
>> http://www.mail-archive.com/user@cassandra.apache.org/msg04831.html
>>
>> Aaron
>>
>>
>> On 29 Jul, 2010,at 12:47 PM, Jianing Hu <jianing@gmail.com> wrote:
>>
>> We recently migrated part of our MySQL database to a 3-node Cassandra
>> cluster with a replication factor of 3. Couple of days ago we noticed
>> that Cassandra sometimes returns the wrong data. Not corrupted data,
>> but data for a different key than the one being asked for. This error
>> appears to be random and intermittent, and happens for maybe every 10K
>> reads. I'm working on a test suite that can reproduce this. Meanwhile
>> just wanted to ask if anyone has seen this problem before? I've tried
>> consistency levels of both QUORUM and ONE, and see the issue with
>> both.
>>
>> Thanks,
>> - Jianing
>>
>