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From sankalp kohli <kohlisank...@gmail.com>
Subject Re: CAS and long lived locks
Date Mon, 24 Jun 2013 20:36:19 GMT
Also CAS is in 2.0 which is not production ready so I am not sure how you
will use it.


On Mon, Jun 24, 2013 at 4:35 PM, sankalp kohli <kohlisankalp@gmail.com>wrote:

> Assuming that database migration is a one time and rare operation, why
> don't you try to grab a lock for a short time. If you are able to grab it,
> then you can renew it for a longer time. This will make sure that in case
> of collision, all contenders wont be locked out for long time.
> You can use Netflix client recipe for locks.
>
>
> On Sat, Jun 22, 2013 at 3:09 PM, Blair Zajac <blair@orcaware.com> wrote:
>
>> Looking at the Cassandra 13 keynote [1], slide 56 regarding hinted writes
>> causing the lock to be taken even though the client thinks the lock attempt
>> failed, which the new CAS support fixes.
>>
>> I have some database migrations to run on Cassandra, so I still need a
>> long lived lock somewhere to prevent two or more migrations running
>> concurrently, so CAS doesn't directly solve this problem.
>>
>> It sounds like I could have a BOOLEAN column named "lock" but use CAS to
>> update it from false or NULL value to true and this avoids the problem of
>> hinted updates problem.  The finally block would reset it to false or NULL.
>>  This would be a simpler implementation than using the wait chain algorithm.
>>
>> Any problems with this?
>>
>> Blair
>>
>> [1] http://www.slideshare.net/**jbellis/cassandra-summit-2013-**keynote<http://www.slideshare.net/jbellis/cassandra-summit-2013-keynote>
>> [2] http://media.fightmymonster.**com/Shared/docs/Wait%20Chain%**
>> 20Algorithm.pdf<http://media.fightmymonster.com/Shared/docs/Wait%20Chain%20Algorithm.pdf>
>>
>
>

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