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Latest Publications

VLDB 2023

Keep CALM and CRDT On

Shadaj Laddad*, Conor Power*, Mae Milano, Alvin Cheung, Natacha Crooks, Joseph M. Hellerstein

Conflict-free replicated datatypes (CRDTs) are a promising line of work that enable coordination-free replication and offer certain eventual consistency guarantees in a relatively simple object-oriented API. Yet CRDT guarantees extend only to data updates; observations of CRDT state are unconstrained and unsafe. We propose an agenda that embraces the simplicity of CRDTs, but provides richer, more uniform guarantees. We extend CRDTs with a query model that reasons about which queries are safe without coordination by applying monotonicity results from the CALM Theorem, and lay out a larger agenda for developing CRDT data stores that let developers safely and efficiently interact with replicated application state.

PDF / arXiv


Katara: Synthesizing CRDTs with Verified Lifting

Shadaj Laddad, Conor Power, Mae Milano, Alvin Cheung, Joseph M. Hellerstein

In this paper, we present Katara, a program synthesis-based system that takes sequential data type implementations and automatically synthesizes verified CRDT designs from them. Katara is able to automatically synthesize CRDTs for a wide variety of scenarios, from reproducing classic CRDTs to synthesizing novel designs based on specifications in existing literature. Crucially, our synthesized CRDTs are fully, automatically verified, eliminating entire classes of common errors and reducing the process of producing a new CRDT from a painstaking paper proof of correctness to a lightweight specification.

PDF / arXiv / GitHub

SOSP SRC 2021 ยท Student Research Competition Winner

Automatic Compartmentalization of Distributed Protocols

David Chu

Consensus protocols are inherently complex and difficult to reason about, and they often become bottlenecks in practice. This has driven the design of scalable protocol variants. Unfortunately, these variants are even more intricate and often error-ridden. The goal of our work is to stop inventing protocols, and instead systematize the scalability ideas from Compartmentalized Paxos so they can be applied automatically to a wide variety of complex protocols, including transactional concurrency control, BFT, etc. Our vision of Automatic Compartmentalization proposes to increase throughput while preserving correctness and liveness, expanding the impact of compartmentalization to a broad range of programs

UC Berkeley Technical Report

Hydroflow: A Model and Runtime for Distributed Systems Programming

Mingwei Samuel, Alvin Cheung, Joseph M. Hellerstein

In this paper we present our ongoing work on Hydroflow, a new cloud programming model used to create constructively correct distributed systems. The model is a refinement and unification of the existing dataflow and reactive programming models. Hydroflow is primarily a low-level compilation target for future declarative cloud programming languages, but developers can use it directly to precisely control program execution or fine-tune and debug compiled programs.

PDF / GitHub

CIDR 2021

New Directions in Cloud Programming

Alvin Cheung, Natacha Crooks, Joseph M. Hellerstein, Mae Milano

In this paper we lay out an agenda for a new generation of cloud programming research aimed at bringing research ideas to programmers in an evolutionary fashion. Key to our approach is a separation of distributed programs into a PACT of four facets: Program semantics, Availablity, Consistency and Targets of optimization. Our agenda raises numerous research challenges across multiple areas including language design, query optimization, transactions, distributed consistency, compilers and program synthesis.

PDF / arXiv