Logless one-phase commit made possible for highly-available datastores

摘要

Highly-available datastores are widely deployed for Internet-based applications. However, many Internet-based applications are not contented with the simple data access interface provided by highly-available datastores. Distributed transaction support is demanded by applications such as massive online payment used by Alipay, Paypal or Baidu Wallet. Current solutions to distributed transaction can spend more than half of the whole transaction processing time in distributed commit. The culprits are the multiple write-ahead logging steps and communication roundtrips in the commit process. This paper presents the HACommit protocol, a logless one-phase commit protocol for highly-available datastores. HACommit has transaction participants vote for a commit before the client decides to commit or abort the transaction; in comparison, the state-of-the-art practice for distributed commit is to have the client decide before participants vote. The change enables the removal of both the participant's write-ahead logging and the coordinator's write-ahead logging steps in the distributed commit process; it also makes possible that, after the client initiates the transaction commit, the transaction data is visible to other transactions within one communication roundtrip time (i.e., one phase). In the evaluation with extensive experiments, HACommit outperforms recent atomic commit solutions for highly-available datastores under different workloads. In the best case, HACommit can commit in one fifth of the time the widely-used two-phase commit (2PC) does.