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Date: Wed, 10 Nov 2010 10:47:49 -0600
Message-ID: <AANLkTi=eLjs2QEPR048M7YsBijqKbd20nf8VpzpdcTBe@mail.gmail.com>
Subject: Re: iteration does not yield all data with consistency ONE
From: Jonathan Ellis <jbellis@gmail.com>
To: user <user@cassandra.apache.org>
Content-Type: text/plain; charset=ISO-8859-1

Interesting.  Does it simplify further to RF=1 and 2 nodes?

On Wed, Nov 10, 2010 at 8:58 AM, Eric van Orsouw
<eric.van.orsouw@eventis.nl> wrote:
> No, all nodes were up and running while the single key was inserted.
> The insert however was with consistency One. I assume however that the replicas are still written in this case.
> It is btw also very reproducible.
>
> -----Original Message-----
> From: Jonathan Ellis [mailto:jbellis@gmail.com]
> Sent: woensdag 10 november 2010 15:44
> To: user
> Subject: Re: iteration does not yield all data with consistency ONE
>
> Was the node that should have the other replica of this row down when
> it was inserted?
>
> On Wed, Nov 10, 2010 at 6:08 AM, Eric van Orsouw
> <eric.van.orsouw@eventis.nl> wrote:
>>
>> Hello,
>>
>>
>>
>> We have a cluster of 4 nodes (0.6.6) and use the random partitioner and a replication of 2.
>>
>> When I insert a number of rows I can always retrieve them by their explicit id (get_range_slices("<key>","", 1).
>>
>> Playing with consistency levels and temporarily shutting down a Cassandra node all yields the expected result.
>>
>>
>>
>> However when I use get_range_slices("","", n) to iterate over all rows, I sometimes don't get anything (depending on the node).
>>
>>
>>
>> I then reduced the problem to inserting just a single row.
>>
>> Specifically, the 'iteration' only seems to succeed when I issue the request to the node that contains the first copy.
>>
>> I Discovered that when I iterate using a consistency level of Quorum/All the iteration always succeeds and I properly get the one row.
>>
>>
>>
>> So a solution would be to always use consistency level One/All but that has a performance penalty.
>>
>>
>>
>> Can anyone explain why iterating using get_range_slices("","",n) does not always function with consistency level One on all nodes?
>>
>>
>>
>> Thanks,
>>
>> Eric
>>
>>
>>
>> P.S. To rule out any discussion on whether or not to use iteration in the first place, we only plan to use it for backup and periodic cleanup cycles.
>
>
> --
> Jonathan Ellis
> Project Chair, Apache Cassandra
> co-founder of Riptano, the source for professional Cassandra support
> http://riptano.com
>


-- 
Jonathan Ellis
Project Chair, Apache Cassandra
co-founder of Riptano, the source for professional Cassandra support
http://riptano.com