consistent hashing -- re-adding a node/replica

Brian Hammond brian at brianhammond.com
Tue Oct 27 19:15:19 EDT 2009


I have a question about consistent hashing you can surely answer in 5  
seconds.

What happens if you take a server out of the hash ring and then re-add  
that same server later?

Won't the data it held before being removed now potentially be "stale"  
as the keys it previously "owned" have been shuffled around to other  
nodes/replicas?  Since the offline node is now back online, the same  
keys that hashed to a different node it its absence will hash to the  
original node again.  Thus, a read of such a key will potentially  
produce stale data.  But that clearly cannot be the case.

I suppose an/the answer is that before entering the hash ring, a node  
is completely cleared/flushed of any data it once held.

I'm reading the original paper now by the way but I need a spoiler.  :)

Thank you.
Brian




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