Efficient Deterministic Concurrency Control Under Practical Isolation Levels

Abstract

Deterministic databases are able to run transactions efficiently in a distributed setting with minimal coordination. Research has shown many benefits from having determinism, from more lightweight database replication, to no/cheaper distributed commit, to high throughput during live migration. Besides those known applications, permissioned blockchain can also be viewed as an application of the deterministic database with security added. A permissioned blockchain maintains a fully-replicated database, where each replica is synchronized by getting blocks of updates. Early permissioned blockchains run a consensus protocol (e.g., PBFT) to agree on the input and rely on the replicas to execute the transactions serially to uphold determinism. Fabric allows concurrent transaction executions but rely on running consensus to agree on the read-write-sets and broadcasting them, which incurs an excessive volume of network traffic. Deterministic concurrency control combines the best of both worlds. It enables solving consensus on the small input, and each replica is able to execute transactions independently with high concurrency. Although powerful, contemporary deterministic databases are still primitive because they support only one isolation level -- Serializable. Furthermore, many deterministic concurrency control schemes are overly pessimistic and cause many unnecessary transaction aborts. These factors motivate us to design DCC, a suite of better deterministic concurrency control schemes, not only for Serializable but also for practical isolation levels beyond Serializable.