Fast Quorum-Based Log Replication and Replay for Fast Databases

The modern In-Memory Database (IMDB) can support highly concurrent OLTP workloads and generate massive transactional logs per second. Quorum based replication protocols such as Paxos or Raft have been widely used in distributed databases. However, it's non-trivial to replicate IMDB because high transaction rate has brought new challenges. First, the leader node in quorum replication should have adaptivity by considering various transaction arrival rates and the processing capability of follower nodes. Second, followers are required to replay logs to catch up the state of the leader in the highly concurrent setting to reduce visibility gap. To this end, we built QuorumX, an efficient quorum-based replication framework for IMDB under heavy OLTP workloads. QuorumX combines critical path based batching and pipeline batching to provide an adaptive log propagation scheme to obtain a stable and high performance at various settings. Further, we propose a safe and coordination-free log replay scheme to minimize the visibility gap between the leader and follower IMDBs. Our evaluation results with the YCSB and TPC-C benchmarks demonstrate that QuorumX achieves the performance close to asynchronous primary-backup replication without sacrificing the data consistency and availability.