I tried to see the problem MVCC with hyperledger fabric but the problem that when I invoke transaction that modifies and reads the same variable with the same key it works.
What are the changes to make to highlight MVCC?
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What are the changes to make to highlight MVCC?
MVCC stands for Multi Value Concurrency Control, this is well know approach to enable optimistic update mechanism which allow to prevent concurrent modifications of the same key. In Fabric context concurrent modification would be transactions which grouped into same block and modifies same key. Therefore in order to experience MVCC failure it's not enough to modify same key several times, you also need to make sure all those transactions will be batched to the same block.
The easiest way to achieve it is to throw as much as possible tx updates to increase probability of transactions to be places into same block.
Artem Barger
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I increase the BatchTimeout in my Configtc.yaml and endorse two transactions that modifies the same key but I didn't have an error – Helmi Trabelsi May 28 '19 at 18:53
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Have you checked transaction status? – Artem Barger May 29 '19 at 06:29
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Thank you for your help, I check the ledger after the excution and i found that the second transaction is commited.But how can I do the check of the transaction status? – Helmi Trabelsi May 29 '19 at 12:47
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You have transactions statuses in block metadata once it has been committed. – Artem Barger May 29 '19 at 12:48
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Yes, the status is 200 that mean that it has been commited – Helmi Trabelsi May 29 '19 at 12:53
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Do you read key value before update? Cause if no read it’s considered a blind write. – Artem Barger May 29 '19 at 12:54
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I do 1- set key1,val1 2- get key1 3- set key2,val2 sleep batchtimeout 4- get key1, the result is val2 – Helmi Trabelsi May 29 '19 at 13:08