Tianjing Xu and Yongqi Zhong, Shanghai Jiao Tong University; Yiming Zhang, Shanghai Jiao Tong University and Shanghai Key Laboratory of Trusted Data Circulation, Governance and Web3; Ruofan Xiong, Xiamen University; Jingjing Zhang, Fudan University; Guangtao Xue and Shengyun Liu, Shanghai Jiao Tong University and Shanghai Key Laboratory of Trusted Data Circulation, Governance and Web3
Consensus and smart contract execution play complementary roles in blockchain systems. Leaderless consensus, as a promising direction in the blockchain context, can better utilize the resources of each node and/or avoid incurring the extra burden of timing assumptions. As modern Byzantine-Fault Tolerant (BFT) consensus protocols can order several hundred thousand transactions per second, contract execution is becoming the performance bottleneck. Adding concurrency to contract execution is a natural way to boost its performance, but none of the existing frameworks is a perfect fit for leaderless consensus.
We propose speculate-order-replay, a generic framework tailored to leaderless consensus protocols. Our framework allows each proposer to (pre-)process transactions prior to consensus, better utilizing its computing resources. We instantiate the framework with a concrete concurrency control protocol Vegeta. Vegeta speculatively executes a series of transactions and analyzes their dependencies before consensus, and later deterministically replays the schedule. We ran experiments under the real-world Ethereum workload on 16vCPU virtual machines. Our evaluation results show that Vegeta achieved up to 7.8× speedup compared to serial execution. When deployed on top of a leaderless consensus protocol with 10 nodes, Vegeta still achieved 6.9× speedup.
