cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Manoj Khangaonkar <khangaon...@gmail.com>
Subject Re: Read/Write consistency issue
Date Sat, 11 Jan 2014 00:54:26 GMT
old is the value that was read from the column.
val is the value that needs to be added to it.
new is (old + val) that is written back to the column.

regards



On Fri, Jan 10, 2014 at 4:36 PM, Andrey Ilinykh <ailinykh@gmail.com> wrote:

> For single thread, consistency ALL it should work. I believe you do
> something different. What are these three numbers exactly?
> old=60616 val =19 new =60635
>
>
> On Fri, Jan 10, 2014 at 1:50 PM, Manoj Khangaonkar <khangaonkar@gmail.com>wrote:
>
>> Hi
>>
>> Using Cassandra 2.0.0.
>> 3 node cluster
>> Replication 2.
>> Using consistency ALL for both read and writes.
>>
>> I have a single thread that reads a value, updates it and writes it back
>> to the table. The column type is big int. Updating counts for a timestamp.
>>
>> With single thread and consistency ALL , I expect no lost updates. But as
>> seem from my application log below,
>>
>> 10 07:01:58,507 [Thread-10] BeaconCountersCAS2DAO [INFO] 1389366000  H
>>  old=59614 val =252 new =59866
>> 10 07:01:58,611 [Thread-10] BeaconCountersCAS2DAO [INFO] 1389366000  H
>>  old=59866 val =252 new =60118
>> 10 07:01:59,136 [Thread-10] BeaconCountersCAS2DAO [INFO] 1389366000  H
>>  old=60118 val =255 new =60373
>> 10 07:02:00,242 [Thread-10] BeaconCountersCAS2DAO [INFO] 1389366000  H
>>  old=60373 val =243 new =60616
>> 10 07:02:00,244 [Thread-10] BeaconCountersCAS2DAO [INFO] 1389366000  H
>>  old=60616 val =19 new =60635
>> 10 07:02:00,326 [Thread-10] BeaconCountersCAS2DAO [INFO] 1389366000  H
>>  old=60616 val =233 new =60849
>>
>> See the last 2 lines of above log.
>> value 60116 is updated to 60635. but the next operation reads the old
>> value 60616 again.
>>
>> I am not using counter column type because it does not support TTL and i
>> hear there are lot of open issues with counters.
>>
>> Is there anything else I can do to further tighten the consistency or is
>> this pattern of high volume read - update - write not going to work in C* ?
>>
>> regards
>> MJ
>>
>> --
>>
>>
>


-- 
http://khangaonkar.blogspot.com/

Mime
View raw message