Towards Concurrency Control On Smart Contract In Blockchain Platforms

The smart contract enables the ability to provide decentralized trusted and consistent storage services in an untrusted distributed environment.However,compared to the traditional centralized database,the current low throughput of the blockchain platform makes it impossible to replace the traditional database in most application scenarios.The low throughput of the blockchain smart contract platform stems from the fact that the current blockchain does not support concurrent execution when executing transactions in the block.In the blockchain network,validators need to deterministically re-execute the block and produce a consistent final state deterministically according to the order of transactions used by the producer.Therefore,the concurrency control algorithms in the traditional DBMS cannot be directly applied to the blockchain due to the non-deterministical nature of their results.Hence by enabling concurrency on smart contracts,especially validation,we can improve the efficiency and the throughput of those platforms.Aiming at the problem of deterministic concurrency control on blockchain smart contracts verification,this thesis proposes a concurrent scheme called MVTO to run smart contracts concurrently by introducing multiversion transaction ordering(MVTO).First,the producer is able to use any concurrency control technique to discover a conflictserializable schedule.then the producer record write set and final status of transactions along with the equivalent serial order of the final schedule into the block.Before validators execute the block,they build an ordered version chain on every conflicting state by using the write sets and the serial order of the transactions,statically defining the priority between conflicting transaction operations.Then they use MVTO based on those version chains to verify the block by replaying this schedule concurrently and deterministically.The evaluation shows that this mechanism achieves approximately 2.5x speedup in the block validation using a thread pool with 3 threads.