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> Dealing with every possible source of non-determinism, re-writing services to be testable/sans-IO [2], etc. takes a lot of engineering effort.

Are there public examples of what such a re-write looks like?

Also, are you working at a rust shop that's developing this way?

Final Note, TigerBeetle is another product that was written this way.

discuss

wwilson|2 years ago

TigerBeetle is actually another customer of ours. You might ask why, given that they have their own, very sophisticated simulation testing. The answer is that they're so fanatical about correctness, they wanted a "red team" for their own fault simulator, in case a bug in their tests might hide a bug in their database!

I gotta say, that is some next-level commitment to writing a good database.

Disclosure: Antithesis co-founder here.

indiv0|2 years ago

Sure! I mentioned a few orthogonal concepts that go well together, and each of the following examples has a different combination that they employ:

- the company that developed Madsim (RisingWave) [0] [1] is tries hardest to eliminate non-determinism with the broadest scope (stubbing out syscalls, etc.)

- sled [2] itself has an interesting combo of deterministic tests combined with quickcheck+failpoints test case auto-discovery

- Dropbox [3] uses a similar approach but they talk about it a bit more abstractly.

Sans-IO is more documented in Python [4], but str0m [5] and quinn-proto [6] are the best examples in Rust I’m aware of. Note that sans-IO is orthogonal to deterministic test frameworks, but it composes well with them.

With the disclaimer that anything I comment on this site is my opinion alone, and does not reflect the company I work at —— I do work at a rust shop that has utilized these techniques on some projects.

TigerBeetle is an amazing example and I’ve looked at it before! They are really the best example of this approach outside of FoundationDB I think.

[0]: https://risingwave.com/blog/deterministic-simulation-a-new-e...

[1]: https://risingwave.com/blog/applying-deterministic-simulatio...

[2]: https://dropbox.tech/infrastructure/-testing-our-new-sync-en...

[3]: https://github.com/spacejam/sled

[4]: https://fractalideas.com/blog/sans-io-when-rubber-meets-road...

[5]: https://github.com/algesten/str0m

[6]: https://docs.rs/quinn-proto/0.10.6/quinn_proto/struct.Connec...