jm + lww   2

Great quote from Voldemort author Jay Kreps
"Reading papers: essential. Slavishly implementing ideas you read: not necessarily a good idea. Trust me, I wrote an Amazon Dynamo clone."

Later in the discussion, on complex conflict resolution logic (as used in Dynamo, Voldemort, and Riak):

"I reviewed 200 Voldemort stores, 190 used default lww conflict resolution. 10 had custom logic, all 10 of which had bugs." --

(although IMO I'd prefer complex resolution to non-availability, when AP is required)
voldemort  jay-kreps  dynamo  cap-theorem  ap  riak  papers  lww  conflict-resolution  distcomp 
november 2014 by jm
The trouble with timestamps
Timestamps, as implemented in Riak, Cassandra, et al, are fundamentally unsafe ordering constructs. In order to guarantee consistency you, the user, must ensure locally monotonic and, to some extent, globally monotonic clocks. This is a hard problem, and NTP does not solve it for you. When wall clocks are not properly coupled to the operations in the system, causal constraints can be violated. To ensure safety properties hold all the time, rather than probabilistically, you need logical clocks.
clocks  time  distributed  databases  distcomp  ntp  via:fanf  aphyr  vector-clocks  last-write-wins  lww  cassandra  riak 
october 2013 by jm

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