Ozone: Fully Out-of-Order Choreographies

Dan Plyukhin, Marco Peressotti, Fabrizio Montesi [2024].
In proceedings of ECOOP 2024, pp. 31:1-31:28.

Abstract

Choreographic programming is a paradigm for writing distributed applications. It allows programmers to write a single program, called a choreography, that can be compiled to generate correct implementations of each process in the application. Although choreographies provide good static guarantees, they can exhibit high latency when messages or processes are delayed. This is because processes in a choreography typically execute in a fixed, deterministic order, and cannot adapt to the order that messages arrive at runtime. In non-choreographic code, programmers can address this problem by allowing processes to execute out of order -- for instance by using futures or reactive programming. However, in choreographic code, out-of-order process execution can lead to serious and subtle bugs, called communication integrity violations (CIVs). In this paper, we develop a model of choreographic programming for out-of-order processes that guarantees absence of CIVs and deadlocks. As an application of our approach, we also introduce an API for safe non-blocking communication via futures in the choreographic programming language Choral. The API allows processes to execute out of order, participate in multiple choreographies concurrently, and to handle unordered or dropped messages as in the UDP transport protocol. We provide an illustrative evaluation of our API, showing that out-of-order execution can reduce latency by overlapping communication with computation.

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@inproceedings{DBLP:conf/ecoop/PlyukhinPM24,
  author       = {Dan Plyukhin and
                  Marco Peressotti and
                  Fabrizio Montesi},
  editor       = {Jonathan Aldrich and
                  Guido Salvaneschi},
  title        = {Ozone: Fully Out-of-Order Choreographies},
  booktitle    = {38th European Conference on Object-Oriented Programming, {ECOOP} 2024,
                  September 16-20, 2024, Vienna, Austria},
  series       = {LIPIcs},
  volume       = {313},
  pages        = {31:1--31:28},
  publisher    = {Schloss Dagstuhl - Leibniz-Zentrum f{\"{u}}r Informatik},
  year         = {2024},
  url          = {https://doi.org/10.4230/LIPIcs.ECOOP.2024.31},
  doi          = {10.4230/LIPICS.ECOOP.2024.31},
  timestamp    = {Mon, 03 Mar 2025 21:02:51 +0100},
  biburl       = {https://dblp.org/rec/conf/ecoop/PlyukhinPM24.bib},
  bibsource    = {dblp computer science bibliography, https://dblp.org}
}

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