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From Sylvain Lebresne <sylv...@datastax.com>
Subject Re: Counters and replication factor
Date Mon, 07 Nov 2011 17:12:13 GMT
This sound like a bug 'a priori'. Do you mind opening a ticket at
https://issues.apache.org/jira/browse/CASSANDRA?
It will help if you can specify which version you are using and the
exact procedure you did that leads to that.
If know how to reproduce, that would be even better.

--
Sylvain

On Mon, Nov 7, 2011 at 5:57 PM, Alain RODRIGUEZ <arodrime@gmail.com> wrote:
> I retried it after restarting all the servers.
> I still have wrong results (I simulated an event 5 times and it was counted
> 3 times by some counters 4 or 5 times by others.
> What I meant by "but now every request returns me always the same count
> value..." will be easier to explain with an example :
> event 1:
> counter1.increment
> counter2.increment
> counter3.increment
> .
> .
> .
> event 5:
> counter1.increment
> counter2.increment
> counter3.increment
> Show results :
> counter1.getValue = returns 4
> counter2.getValue = returns 3
> counter3.getValue = returns 5
> counter1.getValue = returns 5
> counter2.getValue = returns 3
> counter3.getValue = returns 5
> counter1.getValue = returns 4
> counter2.getValue = returns 4
> counter3.getValue = returns 5
> ...
> So I've got wrong values, and not always the same ones. In my previous email
> I tried to tell you by saying "but now every request returns me always the
> same count value..." that I had all the time the same wrong values, let us
> say :
> counter1.getValue = returns 4
> counter2.getValue = returns 3
> counter3.getValue = returns 5
> counter1.getValue = returns 4
> counter2.getValue = returns 3
> counter3.getValue = returns 5
> counter1.getValue = returns 4
> counter2.getValue = returns 3
> counter3.getValue = returns 5
> But that is not true, I still have some "random" wrong values, maybe haven't
> I query to get counter values often enough to see it last time.
> Sorry of not being clearer, that is not easy to explain, neither to
> understand for me.
> Thanks for help.
> Alain
>
> 2011/11/7 Riyad Kalla <rkalla@gmail.com>
>>
>> Alain,
>> When you tried CL.All was that only after you had made the change of
>> ReplicationFactor=3 and restarted all the servers?
>> If you hadn't restarted the servers with the new RF, I am not sure that
>> CL.All would have the intended effect.
>> Also, I wasn't sure what you meant by "but know every request returns me
>> always the same count value..." -- didn't want the requests to always return
>> you the same values?
>> Or maybe you are saying that it always returns the same *wrong* value?
>> Like you do:
>> counter.increment (v=1)
>> counter.increment (v=2)
>> counter.increment (v=3)
>> counter.getValue = returns 7
>> counter.getValue = returns 7
>> counter.getValue = returns 7
>> or something inconsistent like that?
>> On Mon, Nov 7, 2011 at 9:09 AM, Alain RODRIGUEZ <arodrime@gmail.com>
>> wrote:
>>>
>>> I've tried with CL.All, but it doesn't wotk better. I still have strange
>>> values (between 4 and 10 events counted instead of 10) but know every
>>> request returns me always the same count value...
>>> It's very strange.
>>> Any other idea ?
>>> Alain
>>>
>>> 2011/11/7 Riyad Kalla <rkalla@gmail.com>
>>>>
>>>> Alain,
>>>> Try using a CL of 3 or "ALL" and see if that the problem goes away.
>>>> Your replication factor (as I just learned) dictates how many nodes each
>>>> piece of data is replicated to; by using a RF of 3 you are saying "replicate
>>>> all my data to all my nodes" (in this case counters).
>>>> This doesn't happen immediately, but you can *force* it to happen on
>>>> write by specifying a CL of "ALL". If you specify "1" then your counter
>>>> value is written to one member of the ring, then your command returns.
>>>> If you keep querying you will bounce around your ring, reading the
>>>> values from the different nodes until a future date at *which point* all
the
>>>> values will likely agree.
>>>> If you keep all your code you have now exactly the same, just change the
>>>> code at the end where you read the counter value back, to keep reading the
>>>> counter value back every second for 60 seconds and see if all the values
>>>> eventually match up -- they should (as the counter value is replicated to
>>>> all the nodes and their old values discarded).
>>>> -R
>>>>
>>>> On Mon, Nov 7, 2011 at 8:15 AM, Alain RODRIGUEZ <arodrime@gmail.com>
>>>> wrote:
>>>>>
>>>>> Hi,
>>>>> I trying to switch from a RF = 1 to a RF = 3, but I get wrong values
>>>>> from counters when doing so...
>>>>> I got a CF that contains many counters of some events. When I'm at RF
=
>>>>> 1 and simulate 10 events, they are well counted.
>>>>> However, when I switch to a RF = 3, my counter show a wrong value that
>>>>> sometimes change when requested twice (it can return 7, then 5 instead
of 10
>>>>> all the time).
>>>>> I first thought that it was a problem of CL because I seem to remember
>>>>> that I read once that I had to use CL.One for reads and writes with
>>>>> counters. So I tried with CL.One, without success...
>>>>> What am I doing wrong ? Is that some precaution to take when
>>>>> replicating counters ?
>>>>> Alain
>>>
>>
>
>

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