6 research outputs found
Multi-Shot Distributed Transaction Commit
Atomic Commit Problem (ACP) is a single-shot agreement problem similar to consensus, meant to model the properties of transaction commit protocols in fault-prone distributed systems. We argue that ACP is too restrictive to capture the complexities of modern transactional data stores, where commit protocols are integrated with concurrency control, and their executions for different transactions are interdependent. As an alternative, we introduce Transaction Certification Service (TCS), a new formal problem that captures safety guarantees of multi-shot transaction commit protocols with integrated concurrency control. TCS is parameterized by a certification function that can be instantiated to support common isolation levels, such as serializability and snapshot isolation. We then derive a provably correct crash-resilient protocol for implementing TCS through successive refinement. Our protocol achieves a better time complexity than mainstream approaches that layer two-phase commit on top of Paxos-style replication
Reconfigurable Atomic Transaction Commit (Extended Version)
Modern data stores achieve scalability by partitioning data into shards and
fault-tolerance by replicating each shard across several servers. A key
component of such systems is a Transaction Certification Service (TCS), which
atomically commits a transaction spanning multiple shards. Existing TCS
protocols require 2f+1 crash-stop replicas per shard to tolerate f failures. In
this paper we present atomic commit protocols that require only f+1 replicas
and reconfigure the system upon failures using an external reconfiguration
service. We furthermore rigorously prove that these protocols correctly
implement a recently proposed TCS specification. We present protocols in two
different models--the standard asynchronous message-passing model and a model
with Remote Direct Memory Access (RDMA), which allows a machine to access the
memory of another machine over the network without involving the latter's CPU.
Our protocols are inspired by a recent FARM system for RDMA-based transaction
processing. Our work codifies the core ideas of FARM as distributed TCS
protocols, rigorously proves them correct and highlights the trade-offs
required by the use of RDMA.Comment: Extended version of the PODC' 19 paper: Reconfigurable Atomic
Transaction Commi