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I'm doing a cousework for a distributed sytems module, and within it I neef to apply a variable clock incrementor; my tutor has gone over both Lamport and Vector clocks, but said "I cant hint at that" when I asked him about applying a variable length/size per clock.

I wish I knew what to do,

Andy

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1 Answers1

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I suppose you mean vector clocks of variable size?

This is technically not possible due to the way vector clocks are defined and used, however it brings the problem, that you would need to know about all nodes which will communicate together and use a vector clock right in the beginning. This way you wouldn’t be allowed to expand your service, and also if you tear down a node, to never start it again, the time for it would be still sent around and waste resources.

One of my professors in distributed systems mentioned, that Amazon is/was using “dynamic” vector clocks for some services, and they had an algorithm which automatically removed “old” entries from the vector clcoks. They supposesdly concluded something like, this worked so far fine. However I never saw the paper about this.

peter
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  • the dynamo paper talks about using vector clocks. That was many years ago though..not sure what they use internally anymore since they stopped publishing after that. – aspen100 Sep 04 '18 at 15:43