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Re: quick question


Thanks for the response. I finished watching this video but I still got few questions.

1) The speaker seems to suggest that there are different consistency levels being used in different phases of paxos protocol. If so, what is right consistency level to set on these phases?

2) Right now, we just set consistency level as QUORUM at the global level and I dont think we ever change it so in this case what would be the consistency levels being used in different phases.

3) The fact that one should think about reading before the commit phase or after the commit phase (but not any other phase) sounds like there is something special about commit phase and what is that? when I set the QUORUM level consistency at global level Does the commit phase happen right after accept  phase or no? or irrespective of the consistency level when does the commit phase happen anyway? and what happens during the commit phase?


On Wed, Feb 1, 2017 at 3:30 AM, Alain RODRIGUEZ <arodrime@xxxxxxxxx> wrote:

I believe that this talk from Christopher Batey at the Cassandra Summit 2016 might answer most of your questions around LWT: https://www.youtube.com/watch?v=wcxQM3ZN20c

He explains a lot of stuff including consistency considerations. My understanding is that the quorum read can only see the data written using LWT after the commit phase. A SERIAL Read would see it (video, around 23:40).

Here are the slides as well: http://fr.slideshare.net/DataStax/light-weight-transactions-under-stress-christopher-batey-the-last-pickle-cassandra-summit-2016

Let us know if you still have questions after watching this (about 35 minutes).

Alain Rodriguez - @arodream - alain@xxxxxxxxxxxxxxxxx

The Last Pickle - Apache Cassandra Consulting

2017-02-01 10:57 GMT+01:00 Kant Kodali <kant@xxxxxxxxxxxx>:
When you initiate a LWT(write) and do a QUORUM read is there a chance that one might not see the LWT write ? If so, can someone explain a bit more?