CRDTs #2: Turtles All the Way Down
67 points
13 days ago
| 2 comments
| jhellerstein.github.io
| HN
AstralStorm
12 days ago
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Doesn't the consistent versioning approach make for eventual consistency which might never arrive? Suppose you have a node where tombstones never work...

The missing part is monitoring error conditions when it times out... Which also should be resistant to byzantine failure, so more than one monitor voting on it.

And when that happens you have to force stop the node or multiple thereof, diagnose which direction the consistency failed etc.

You need to have a well defined requirement set on the consistency and timeliness in the first place.

As far as turtles, assumption of faultlessness (of storage, of networking, of whole distributed machines, of the power supply) is one of these. The moment your CRDT starts to involve backups things get funny.

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holmesworcester
13 days ago
[-]
What a great post! The section on expiring tombstones is a great illustration of the overall point and also helpful in practice.
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