incubator-cassandra-dev mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Jonathan Ellis <jbel...@gmail.com>
Subject Re: [jira] Commented: (CASSANDRA-48) test-and-set
Date Fri, 03 Apr 2009 16:18:15 GMT
That makes sense.

In that case you would have to do a read that waits for all replicas.
Which will hurt availability but I don't see any alternative.

Again, this isn't intended going to provide strong consistency.  You
can still come up with failure scenarios where inconsistent data could
be read temporarily.  I'm not sure if it's going to be useful given
that.

On Fri, Apr 3, 2009 at 10:10 AM, Sandeep Tata <sandeep.tata@gmail.com> wrote:
> Well, the test and set failed could have failed because of a new value
> replacing the old one since this client read it.
> Jun is talking about re-reading to get this new value and retrying the
> "transaction"
>
> On Fri, Apr 3, 2009 at 9:08 AM, Jonathan Ellis (JIRA) <jira@apache.org> wrote:
>>
>>    [ https://issues.apache.org/jira/browse/CASSANDRA-48?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12695470#action_12695470
]
>>
>> Jonathan Ellis commented on CASSANDRA-48:
>> -----------------------------------------
>>
>> The client should not do that.  It knows the old version (or it couldn't be doing
test-and-set) and it knows the new version and it knows that not all replicas were written
but some were.  Doing a read cannot possibly tell it anything it doesn't already know.
>>
>>> test-and-set
>>> ------------
>>>
>>>                 Key: CASSANDRA-48
>>>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-48
>>>             Project: Cassandra
>>>          Issue Type: Improvement
>>>            Reporter: Jonathan Ellis
>>>
>>> Atomic test-and-set insert operation would be nice: "set value to X but only
if the current value is still Y."  This allows a sort of optimistic consistency: perform
a GET, then perform test-and-set with the value of that GET as Y.
>>> I do not think that this requires strong consistency to be useful.
>>
>> --
>> This message is automatically generated by JIRA.
>> -
>> You can reply to this email to add a comment to the issue online.
>>
>>
>

Mime
View raw message