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Comment by anonymousDan | Hacker News Reader

Does Jepsen ever open source any of their tooling/test harnesses? I teach a distributed systems class and it would be great to have an automated test framework/tools for Distributed systems issues

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Yes: the library is prominently linked on the home page, and there are deep links to the Dgraph test suite code throughout the report. Pretty much all of my work is OSS, and public release of test harness for each report is explicitly part of the Jepsen ethics policy. :)

https://github.com/jepsen-io https://jepsen.io/ https://jepsen.io/ethics

Awesome! Quick question - how much of the test harness you use for each report is generic/reusable, and how much is system specific? I have my students implement various algorithms/systems in Elixir e.g. Raft/Paxos, various broadcast algs etc. It would be nice to have something both they and I could use to simulate network partitions etc.

Kinda depends on what you're doing, how much of Jepsen you're using, and how complex the system-specific code is. You can write a minimal Jepsen test in ~100 lines of code, if that's helpful. Jepsen and its main supporting libraries (Elle and Knossos) clock in at about 19K lines of code; a little over six years of full-time work.

For simulation testing, I'd suggest looking at Maelstrom, which uses Jepsen to provide a sort of workbench for writing toy Raft implementations in any language. You give it a binary which takes messages as JSON on STDIN and emits messages to STDOUT; it spawns a bunch of "nodes" (local processes) of that binary, connects them via a simulated network, generates pathological network behavior, simulates client requests, and verifies the resulting histories with Jepsen.

https://github.com/jepsen-io/maelstrom

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