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From Sylvain Lebresne <sylv...@datastax.com>
Subject Re: possible 'coming back to life' bug with counters
Date Wed, 15 Jun 2011 09:34:27 GMT
Let me point out that the current thread is about counter removal, not about
counter TTL. Counter expiration have other problems, so that even if you do not
care about incrementing a counter again after it expires, it will
still not work for you
(please look at the discussion on
https://issues.apache.org/jira/browse/CASSANDRA-2103
do details).

As for solutions, people are looking to specific compaction strategy
to achieve something
roughly similar to expiring counters (see
https://issues.apache.org/jira/browse/CASSANDRA-2735
for instance).

--
Sylvain

On Wed, Jun 15, 2011 at 8:29 AM, Viktor Jevdokimov
<vjevdokimov@gmail.com> wrote:
> What if it is OK for our case and we need counters with TTL?
> For us Counters and TTL both are important. After column is expired it is
> not important what value counter will have.
> Scanning millions rows just to delete expired ones is not a solution.
>
> 2011/6/14 Sylvain Lebresne <sylvain@datastax.com>
>>
>> As listed here: http://wiki.apache.org/cassandra/Counters, counter
>> deletion is
>> provided as a convenience for permanent deletion of counters but, because
>> of the design of counters, it is never safe to issue an increment on a
>> counter that
>> has been deleted (that is, you will experience back to life behavior
>> sometimes in
>> that case).
>> More precisely, you'd have to wait long enough after a deletion to start
>> incrementing the counter again. But in the worst cases, long enough is
>> something
>> like gc_grace_seconds + major compaction.
>>
>> This is *not* something that is likely to change anytime soon (I don't
>> think this is
>> fixable with the current design for counters).
>>
>> --
>> Sylvain
>>
>> On Sat, Jun 11, 2011 at 3:54 AM, David Hawthorne <dhawth@3crowd.com>
>> wrote:
>> > Please take a look at this thread over in the hector-users mailing list:
>> >
>> > http://groups.google.com/group/hector-users/browse_thread/thread/99835159b9ea1766
>> > It looks as if the deleted columns are coming back to life when they
>> > shouldn't be.
>> > I don't want to open a bug on something if it's already got one that I
>> > just
>> > couldn't find when I scanned the list of open bugs.
>> > I'm using hector 0.8 against cassandra 0.8 release.  I can give you
>> > whatever
>> > logs or files you'd like.
>
>

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