Re: MVCC Error Round 3 - Profile 2org1peergoleveldb

Prasanth Sundaravelu

It is correct.
Example for Ali's explanation

Tx1: Key read version: 1, Key version after write: 2 (still not yet commited) 

Tx2: Key read version: 1, Key version after write: 2 (not commited)

Tx1 gets commited. Current key version: 2

Tx2 fails. Cuz latest version is 2 and it is trying to update 1.

On Wed, 20 May 2020, 6:43 am Ali Abdulaziz, <aakzubaidi@...> wrote:
To my understanding, consider this (Key, Value, version).
for every successful update on a key, both values and the version are changes, such that the value will be committed, and the version is increased by one.
So, it can happen that, a current transaction is reading a key, which version say is 5 and the value is 10 for example. During that, it happens that an in-flight transaction managed to be committed, causing the version to be 6 now instead of 5. 
Now, back to that transaction that is currently trying to update a key based on version 5, agnostic to what happened to the key meanwhile. 
When peers try to commit the current transaction, there will the conflict of the version occurs. 
This is my attempt to explain the MVCC conflict. Again, this is my own impression, which needs to be confirmed by others with more insight on the matter. 


Ali Alzubaidi

On Tue, 19 May 2020 at 08:43, Prasanth Sundaravelu <prasanths96@...> wrote:
It's a classic error that prevents double spending / race condition.

You must be trying to update the same key over and over when loading it with transactions. To avoid it, you may update one different key every transaction. 

On Tue, 19 May 2020, 1:04 pm Yogita Lande, <yogita.lande@...> wrote:

Forwarded Conversation
Subject: MVCC Error Round 3 - Profile 2org1peergoleveldb

From: Lande Yogita Bhaskarrao <LB00470913@...>
Date: Tue, May 19, 2020 at 11:45 AM
To: perf-and-scale-wg@... <perf-and-scale-wg@...>
Cc: Yogita Lande <yogita.lande@...>

Dear Team,


We are getting below error, while trying Caliper version 0.3.0 in round 3.

Could you please advise whether all the transactions should pass and there shouldn’t be any failure.


Please do let me know if more information is required.



Thanks and Regards,


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From: Lande Yogita Bhaskarrao <LB00470913@...>
Date: Tue, May 19, 2020 at 11:47 AM
To: perf-and-scale-wg+help@... <perf-and-scale-wg+help@...>
Cc: Yogita Lande <yogita.lande@...>

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