Atomicity of if_not_modified?

qaspar snooper77 at gmail.com
Sat Jan 5 03:45:35 EST 2013


Justin Sheehy wrote
> On Jan 4, 2013, at 1:25 PM, Les Mikesell wrote:
> 
>> And, doesn't every description of riak behavior have to include the
>> scenario where the network is partitioned and updates are
>> simultaneously performed by entities that can't contact each other?
>> If it weren't for that possibility, it could just elect a master and
>> do real atomic operations.
> 
> Yes, absolutely.
> 
> There are no atomic compare-and-set operations available from Riak,
> regardless of headers and R/W values.
> 
> Conditional HTTP requests are present because they are "free" due to
> Webmachine, and they are sometimes useful, but should not be seen as
> semantically very different from the client doing a read itself to decide
> whether to write.
> 
> -Justin

Agreed. But I think the split-brain scenario could be avoided by setting
DW=DR=2 in addition, in which case at most one call to one of the partitions
can succeed - correct?

Kaspar





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