incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Benjamin Black...@b3k.us>
Subject Re: questions regarding read and write in cassandra
Date Fri, 20 Aug 2010 02:56:59 GMT
More recent.  Newest timestamp always wins.  And I am moving this to
the user list (again) so it can be with all its friendly threads on
the exact same topic.

On Thu, Aug 19, 2010 at 10:22 AM, Maifi Khan <maifi.khan@gmail.com> wrote:
> Hi David
> Thanks for your reply.
> But what happens if I read and get 2 nodes has value 10 with older
> time stamp and the third node has 20 with more recent time stamp?
> Will cassandra return 10(majority) or 20(more recent)?
>
> thanks
> Maifi
>
> On Thu, Aug 19, 2010 at 1:20 PM, David Timothy Strauss
> <david@fourkitchens.com> wrote:
>> The quorum write would fail, but the data would not be rolled back. Assuming the
offline nodes recover, the data would eventually replicate.
>>
>> This question belongs on the user list, though.
>>
>> -----Original Message-----
>> From: Maifi Khan <maifi.khan@gmail.com>
>> Date: Thu, 19 Aug 2010 13:00:47
>> To: <dev@cassandra.apache.org>
>> Reply-To: dev@cassandra.apache.org
>> Subject: questions regarding read and write in cassandra
>>
>> Hi
>> I have a question in the following scenario.
>> Say we have 10 nodes, Replication factor is 5.
>> Now, say, for Row X, Column Y, data is replicated to node 1,2,3,4,5
>> and current value is 10
>> Say, I issue a write command with value “20” to Row X, column Y with
>> quorum(n/2+1=3 nodes).  Say it updated 1 and 2 and failed to update
>> any other node. So it failed to write to 3 nodes. What happens in such
>> scenario?
>>
>> Q: Will the user returned failed?
>>
>> Now, assuming that the write failed.
>> What value will I see if I want to read the same cell with Quorum?
>> Now, say I read the data with quorum. It read from 1, 4, 5 and see
>> that node 1 has the most recent data (“20” which is still there as
>> cassandra does not roll back).
>> Will it will return the data “20” to the user or will it return the
>> earlier value 10 as it is returned by the node 4 and 5?
>>
>> Also, does read repair tries to propagate 20 to all the replicas
>> although cassandra returned failed to the user?
>>
>>
>> thanks
>>
>

Mime
View raw message