[jira] [Created] (S2GRAPH-68) Refactor write-write conflict resolving logic

["DOYUNG YOON (JIRA)" <ji...@apache.org>]

DOYUNG YOON created S2GRAPH-68:
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             Summary: Refactor write-write conflict resolving logic
                 Key: S2GRAPH-68
                 URL: https://issues.apache.org/jira/browse/S2GRAPH-68
             Project: S2Graph
          Issue Type: Improvement
            Reporter: DOYUNG YOON
            Assignee: DOYUNG YOON


Current implementation for resolving write-write conflict on snapshotEdge is overwhelmingly complicated, so I am suggesting refactor this to make it easy to understand.

Current master test cases failed with positive fail probability for RPC(hbase.fail.prob=0.01).

I can reproduce it by running `sbt "project s2core" -Dconfig.file=s2rest_play/conf/test.conf test`.

We can think this problem as critical section problem. Multiple thread that want to mutate same SnapshotEdge can only proceed one-by-one to keep consistent view on related IndexEdge. To achieve this, we are storing extra data on SnapshotEdge. 

Details are on [gitbook|https://steamshon.gitbooks.io/s2graph-book/content/request_state_diagram.html].

I think following 3 things would be expected output after resolving this issue.

1. more comments and simplified code.
2. remove excessive re-fetch on every retry from partial failure. since it is guaranteed that only one thread can proceed at a time, re-fetch is not necessary.
3. remove Thread.sleep between retry from partial failure.





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