See http://www.snookles.com/scotttmp/MyFirstMachiAnimation.mov for
a very crude animation of a simulated network partition scenario.
The animation is about 3.3 MBytes, but it's served by a 5 Mbit/sec
network link, please be gentle & patient.
Green = UPI/fully-in-sync part of the chain
Purple = "Repair" part of the chain
Grey = A limited # of older epochs are superimposed to
demonstrate disagreement at this instant in time
We have an asymmetric partition: 'c' can't send messages to 'a',
but all other message passing is OK. These "private" epochs are
thrashing between different views of the cluster, each author server
making the same proposal over & over again.
Author a: [b,a,c,d], epochs=524,528,530,532
Author b: [b,a,c,d], epochs=522,525,527,529,531
Author c: [b,c,d], epochs=521,523,526
Author d: [b,a,c,d], epochs=533
Finally, when the network partition disappears at epoch=533, everyone
quickly makes the same decision on how to heal the cluster.
The number of edges show the agreement (or lack thereof) of which
epoch proposal is "in use" by a participant. The letter labels at
the base of each arrow indicate the source/user of that edge.
No, there is no replication to one's self, e.g. epoch=536. I've put that
there to try extra emphasis that it's a chain of length 1.
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