Using broadcast primitives in replicated databases

Abstract

We explore the use of different variants of broadcast protocols for managing replicated databases. Starting with the simplest broadcast primitive, the reliable broadcast protocol, we show how it can be used to ensure correct transaction execution. The protocol is simple, and has several advantages, including prevention of deadlocks. However, it requires a two-phase commitment protocol for ensuring correctness. We then develop a second protocol that uses causal broadcast and avoids the overhead of two-phase commit by exploiting the causal delivery properties of the broadcast primitives to implicitly collect the relevant information used in two-phase commit. Finally, we present a protocol that employs atomic broadcast and completely eliminates the need for acknowledgements during transaction commitment.