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Add a bit of interpretation advice for the chain manager simulator

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Scott Lystig Fritchie 2015-03-04 13:01:38 +09:00
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prototype/chain-manager/README.md
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@ -164,3 +164,39 @@ In summary:
* Run the algorithm, wait for everyone to settle on a **unanimous value**
of some ordering of all four FLUs.
To try to understand the simulator's output, let's look at some examples:
20:12:59.120 c uses: [{epoch,1023},{author,d},{upi,[c,b,d,a]},{repair,[]},{down,[]},{d,[{author_proc,react},{ps,[]},{nodes_up,[a,b,c,d]}]},{d2,[{network_islands,[[a,b,c,d]]},{hooray,{v2,{2015,3,3},{20,12,59}}}]}]
So, server C has decided the following, as far as it can tell:
* Epoch 1023 is the latest epoch
* There's already a projection written to the "public" projection stores by author server D.
* C has decided that D's proposal is the best out of all that C can see in the "public" projection stores plus its own calculation
* The UPI/active chain order is: C (head), B, D, A (tail).
* No servers are under repair
* No servers are down.
* Then there's some other debugging/status info in the 'd' and 'd2' data attributes
* The 'react' to outside stimulus triggered the author's action
* The 'ps' says that there are no network partitions *inside the simulator* (yes, that's cheating, but sooo useful for debugging)
* All 4 nodes are believed up
* (aside) The 'ps' partition list describes nodes that cannot talk to each other.
* For easier debugging/visualization, the 'network_islands' converts 'ps' into lists of "islands" where nodes can talk to each other.
* So 'network_islands' says that A&B&C&D can all message each other, as far as author D understands at the moment.
* Hooray, the decision was made at 20:12:59 on 2015-03-03.
So, let's see a tiny bit of what happens when there's an asymmetric
network partition. Note that no consensus has yet been reached:
participants are still churning/uncertain.
20:12:48.420 a uses: [{epoch,1011},{author,a},{upi,[a,b]},{repair,[d]},{down,[c]},{d,[{author_proc,react},{ps,[{a,c}]},{nodes_up,[a,b,d]}]},{d2,[{network_islands,[na_reset_by_always]},{hooray,{v2,{2015,3,3},{20,12,48}}}]}]
20:12:48.811 d uses: [{epoch,1012},{author,d},{upi,[a]},{repair,[b,c,d]},{down,[]},{d,[{author_proc,react},{ps,[{a,c}]},{nodes_up,[a,b,c,d]}]},{d2,[{network_islands,[na_reset_by_always]},{hooray,{v2,{2015,3,3},{20,12,48}}}]}]
{FLAP: a flaps 5}!
* The simulator says that the one-way partition definition is `{ps,[{a,c}]}`. This is authoritative info from the simulator. The algorithm *does not* use this source of info, however!
* Server A believes that `{nodes_up,[a,b,d]}`. A is a victim of the simulator's partitioning, so this belief is correct relative to A.
* Server D believes that `{nodes_up,[a,b,c,d]}`. D doesn't have any simulator partition, so this belief is also correct relative to D.
* A participant has now noticed that server A has "flapped": it has
proposed the same proposal at least 5 times in a row. This kind of
pattern is indicative of an asymmetric partition ... which is indeed
what is happening at this moment.