Discussion
OK, who are the experts on #DistributedSystems on the #Fediverse? There is a new #FEP for implementing a scalar #LogicalClock in #ActivityPub, #FEP4f18.
I'm especially interested in mitigations for Byzantine faults in the system; right now, it's kind of hand-wavy based on value and trust heuristics:
@evan WRT Byzantine faults, it looks like, with the FEP algorithm, the logical clock will never recover if a node accidentally or intentionally sends a very high clock value (e.g., 2^64-1). What is the motivation for having a logical clock for the AP network?
@Steve_Bate hey, Steve. So, there is a security considerations section here:
https://fediverse.codeberg.page/fep/fep/4f18/#security-considerations
Like I mentioned, the best mitigations I have are heuristic: don't advance the clock more than the expected number of activities per day, say and/or don't advance the clock at all on activities from known defector servers.
@Steve_Bate logical clocks let you track some kinds of causality in distributed systems.
https://en.wikipedia.org/wiki/Logical_clock
The scalar logical clock in #FEP4f18 is similar in intent and design to Lamport clocks:
@Steve_Bate Lamport's original paper is readable and gives some good motivations:
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