Due to regulatory compliance and governance management, modern (permissioned) blockchains require flexible endorsement, which allows the endorsement policy for each contract or state object to be individually defined. To enable flexible endorsement, Hyperledger Fabric employs an execute-order-validate (EOV) paradigm, in which transactions first undergo speculative execution and endorsement, and are only then ordered and validated. Meanwhile, most blockchain systems, including the platform targeted in this work (i.e., ChainMaker), still follow a conflict-free order-execute framework. We argue that the EOV paradigm still faces several limitations, notably high abort rates in high-contention workloads such as those in Decentralized Finance (DeFi). To avoid refactoring our system and better suit DeFi applications, we try to integrate flexible endorsement into the classical order-execute architecture and accordingly propose a new framework. The key challenge is to deterministically remove problematic transactions from an ordered list, while preserving censorship resistance and decentralization for the remaining ones. We instantiate this framework on top of Tendermint, a seminal Byzantine fault-tolerant (BFT) protocol adopted in our system, and thereby propose FlexTender. By elegantly embedding endorsements into consensus, FlexTender incurs no additional messaging overhead in the normal case. Empirical evaluation using an Ethereum USDT workload demonstrates that FlexTender achieves up to $10.6\times$ speedup in throughput over an EOV simulation on the same platform.

翻译：由于合规监管和治理管理的需求，现代（许可型）区块链需要灵活的背书机制，允许针对每个合约或状态对象单独定义背书策略。为实现灵活背书，Hyperledger Fabric采用了执行-排序-验证（EOV）范式，交易先经过推测性执行和背书，随后才进行排序和验证。与此同时，包括本工作目标平台（即ChainMaker）在内的大多数区块链系统仍遵循无冲突的执行-排序框架。我们认为EOV范式仍面临若干局限，尤其是在去中心化金融（DeFi）等高冲突工作负载下会出现高中止率。为避免重构系统并更好地适配DeFi应用，我们尝试将灵活背书融入经典执行-排序架构，并提出一种新框架。核心挑战在于从有序列表中确定性地剔除问题交易，同时保留剩余交易的抗审查性和去中心化特性。我们在系统中采用的里程碑式拜占庭容错（BFT）协议Tendermint上实例化该框架，从而提出FlexTender。通过将背书优雅地嵌入共识过程，FlexTender在正常情形下不引入额外消息开销。基于以太坊USDT工作负载的实验评估表明，在同一平台上，FlexTender相较于EOV模拟方案可实现高达10.6倍的吞吐量提升。