we should put in a test for that. it is certainly a plausible scenario. in theory it will just flow into the next epoch and everything will be fine, but we should try it and see.


On 10/19/2010 11:33 AM, Sandy Pratt wrote:
Just as a thought experiment, I was pondering the following:

ZK stamps each change to its managed state with a zxid 
(http://hadoop.apache.org/zookeeper/docs/r3.2.1/zookeeperInternals.html).  That 
ID consists of a 64 bit number in which the upper 32 bits are the epoch, which 
changes when the leader does, and the bottom 32 bits are a counter, which is 
incremented by the leader with every change.  If 1000 changes are made to ZK 
state each second (which is 1/20th of the peak rate advertised), then the 
counter portion will roll over in 2^32 / (86400 * 1000) = 49 days.

Now, assuming that my math is correct, is this an actual concern?  For example, 
if I'm using ZK to provide locking for a key value store that handles 
transactions at about that rate, am I setting myself up for failure?



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