cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Sylvain Lebresne <sylv...@datastax.com>
Subject Re: for counters: does read have to be ALL ?
Date Fri, 04 Feb 2011 08:22:32 GMT
On Thu, Feb 3, 2011 at 10:39 PM, Yang <teddyyyy123@gmail.com> wrote:

> the pdf at the design doc
>
> https://issues.apache.org/jira/secure/attachment/12459754/Partitionedcountersdesigndoc.pdf
>
> does say so:
> page 2 "- strongly consistent read: requires consistency level ALL.
> (QUORUM is insufficient.)
> "
>
> but the wiki  http://wiki.apache.org/cassandra/Counters
> gave a code example:
>
> rv = client.get_counter('key1', ColumnPath(column_family='Counter1',
> column='c1'), ConsistencyLevel.ONE)
>
>
> is one of them wrong?
>

Three things:
First, the design doc is talking of strongly consistent reads, the wiki
gives
a simple exemple of a read (it's even followed with a warning) so there is
no actual contradiction here.

Second, and more to the point, the design docs are slightly outdated, on
this point at least. There is now support for QUORUM (or ALL) writes (since
https://issues.apache.org/jira/browse/CASSANDRA-1944), so you have the
usual consistency guarantee (i.e, you get strong consistency with QUORUM
(resp. ONE) read provided you wrote at QUORUM (resp. ALL)).

Third, it is good to recall that counters are not considered stable yet
(that
includes the documentations).

--
Sylvain


> Thanks
> Yang
>

Mime
View raw message