Sure! I will  move further questions to JIRA. Thanks

On Thu, Nov 3, 2016 at 4:34 AM, Benjamin Lerer <benjamin.le...@datastax.com>
wrote:

> I really have to look at the code of the different versions first to answer
> your questions.
> I will put as much as information as I can in the ticket but feel free to
> ask more questions in the ticket if you need to.
>
> Benjamin
>
> On Wed, Nov 2, 2016 at 10:58 PM, Bhaskar Muppana <mgvbhas...@gmail.com>
> wrote:
>
> > Thanks Benjamin! I am also hoping to ask couple of questions on
> difference
> > in this code base between 2.0, 2.1 and 3.0. I understand 2.0 is closed
> from
> > community point of view. But, we are still using in some cases, so we
> need
> > to fix it internally.
> >
> > With my limited understanding of the code, it looks like to me there is
> no
> > protection against short reads in 2.0. But in 3.0, we seem to have some
> > short read transformation. At least, from comments it feels like that
> code
> > should have taken care of cases like this. So this must be a bug in 3.0
> > code, where as in 2.0 the complete feature for short read protection is
> > missing. Is my understanding right? Can you please shed more light on
> this?
> >
> > I have created a JIRA as you asked -
> > https://issues.apache.org/jira/browse/CASSANDRA-12872
> >
> > This is my first JIRA, so I don't know conventions to set priority. As
> its
> > data inconsistency issue, I believe this is critical. Feel free to change
> > the priority according to community conventions.
> >
> > Thanks,
> > Bhaskar
> >
> > On Wed, Nov 2, 2016 at 1:26 AM, Benjamin Lerer <
> > benjamin.le...@datastax.com>
> > wrote:
> >
> > > Hi Bhaskar,
> > >
> > > Thanks for reporting that problem. It is a nice catch :-)
> > >
> > > Could you open a JIRA ticket with all the information that you
> provided?
> > >
> > > I will try to fix that problem.
> > >
> > > Benjamin
> > >
> > >
> > > On Wed, Nov 2, 2016 at 12:00 AM, Bhaskar Muppana <mgvbhas...@gmail.com
> >
> > > wrote:
> > >
> > > > Hi Guys,
> > > >
> > > > We are seeing an issue with paging reads missing some small number of
> > > > columns when we do paging/limit reads. We get this on a single DC
> > cluster
> > > > itself when both reads and writes are happening with QUORUM.
> > Paging/limit
> > > > reads see this issue. I have attached the ccm based script which
> > > reproduces
> > > > the problem.
> > > >
> > > > * Keyspace RF - 2
> > > > * Table (id int, course text, marks int, primary key(id, course))
> > > > * replicas for partition key 1 - r1, r2 and r3
> > > > * insert (1, '1', 1) ,  (1, '2', 2),  (1, '3', 3),  (1, '4', 4),  (1,
> > > '5',
> > > > 5) - succeeded on all 3 replicas
> > > > * insert (1, '6', 6) succeeded on r1 and r3, failed on r2
> > > > * delete (1, '2'), (1, '3'), (1, '4'), (1, '5') succeeded on r1 and
> r2,
> > > > failed on r3
> > > > * insert (1, '7', 7) succeeded on r1 and r2, failed on r3
> > > >
> > > > Local data on 3 nodes looks like as below now
> > > >
> > > > r1: (1, '1', 1), tombstone(2-5 records), (1, '6', 6), (1, '7', 7)
> > > > r2: (1, '1', 1), tombstone(2-5 records), (1, '7', 7)
> > > > r3: (1, '1', 1),  (1, '2', 2),  (1, '3', 3),  (1, '4', 4),  (1, '5',
> > > > 5), (1, '6', 6)
> > > >
> > > > If we do a paging read with page_size 2, and if it gets data from r2
> > and
> > > > r3, then it will only get the data (1, '1', 1) and (1, '7', 7)
> skipping
> > > > record 6. This problem would happen if the same query is not doing
> > paging
> > > > but limit set to 2 records.
> > > >
> > > > Resolution code for reads works same for paging queries and normal
> > > > queries. Co-ordinator shouldn't respond back to client with
> > > records/columns
> > > > that it didn't have complete visibility on all required replicas (in
> > this
> > > > case 2 replicas). In above case, it is sending back record (1, '7',
> 7)
> > > back
> > > > to client, but its visibility on r3 is limited up to (1, '2', 2) and
> it
> > > is
> > > > relying on just r2 data to assume (1, '6', 6) doesn't exist, which is
> > > > wrong. End of the resolution all it can conclusively say any thing
> > about
> > > is
> > > > (1, '1', 1), which exists and (1, '2', 2), which is deleted.
> > > >
> > > > Ideally we should have different resolution implementation for
> > > > paging/limit queries.
> > > >
> > > > We could reproduce this on 2.0.17, 2.1.16 and 3.0.9.
> > > >
> > > > Seems like 3.0.9 we have ShortReadProtection transformation on list
> > > > queries. I assume that is to protect against the cases like above.
> But,
> > > we
> > > > can reproduce the issue in 3.0.9 as well.
> > > >
> > > > Thanks,
> > > > Bhaskar
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > > >
> > >
> >
>

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