Chorex: Restartable, Language-Integrated Choreographies

TL;DR

Chorex is a novel choreographic programming language for Elixir that enables robust distributed applications by supporting actor failure recovery, static error detection, and tight language integration.

Contribution

It introduces failure-tolerant choreographies in Elixir, demonstrating implementation via metaprogramming and providing static error reporting within the host language.

Findings

Chorex effectively recovers from actor crashes using checkpoints.

It integrates choreographies tightly with Elixir, enabling static error detection.

Overhead of checkpointing is measured and analyzed.

Abstract

We built Chorex, a language that brings choreographic programming to Elixir as a path toward robust distributed applications. Chorex is unique among choreographic languages because it tolerates failure among actors: when an actor crashes, Chorex spawns a new process, restores state using a checkpoint, and updates the network configuration for all actors. Chorex also proves that full-featured choreographies can be implemented via metaprogramming, and that doing so achieves tight integration with the host language. For example, mismatches between choreography requirements and an actor implementation are reported statically and in terms of source code rather than macro-expanded code. This paper illustrates Chorex on several examples, ranging from a higher-order bookseller to a secure remote password protocol, details its implementation, and measures the overhead of checkpointing. We conjecture that Chorex's projection strategy, which outputs sets of stateless functions, is a viable approach for other languages to support restartable actors.