dark VS rr

Yes. Darklang was originally in OCaml using js_of_ocaml, and we ported it to F# using Blazor (https://github.com/darklang/dark/tree/main/backend/src/Wasm). It works.

We found that in dotnet 6, the code was much slower, with long startup times and a much bigger download, than in js_of_ocaml. It also had a lot of issues in running in a Webworker, which wasn't the case for js_of_ocaml.

In dotnet 7, the webworker issues are better and AOT is easier, so startup is faster. Download sizes are still bad, and it's still slower than js_of_ocaml.

However, dotnet allows almost any code to run in WASM, which js_of_ocaml had large limitations. This meant a decent chunk of functionality had to be worked around to make separate js vs native targets, which also was a massive pain and took a long time. Dune's virtual targets wasn't ready at the time - I think we were one of the test cases for it.

Why should I use this instead of https://darklang.com/

First it was probably Dark. They made a lot of noise some years ago, but then I never heard of them again (looking at their current website, looks like they moved on to AI now, obviously).

Reminds me of Darklang. Personally, I don't think vendoring cloud services into a language is going to be beneficial. I'm curious how the language deals with vendor updates. Do I have to upgrade the language then? If so, I see a lot conflicts coming from this. Then it comes down to Javascript or HCL, the HCL bit makes me think that the below statement is not as truthy as it is on the surface:

We still don't have all that many users (~100 active), so I'm not sure you'll find an answer here. But we collect that sort of feedback publicly, which might answer your question: https://github.com/darklang/dark/discussions/categories/feed...

I wish I could remember what took me to YCombinator's website on the 10th of October, 2022. That was when I first heard about Wasp and another language called DarkLang. After I learned about Wasp, I was intrigued and curious to know how it works, which led me to join the discord server the next day.

Some languages that try to integrate an HTTP server and a database:

Ur/Web: http://impredicative.com/ur/

Dark (Darklang): https://darklang.com/

There are others in this space I did not assess like Encore, Shuttle, Modal, and Dark. These were not assessed for the sake of time. If you're interested in IfC, I encourage you to take a look at these others.

Oh, finally! I was waiting to build my serverless CRUD webapp in Dark (OCaml + JavaScript and Fsharp?) until they had support for returning negative numbers on a GET request!

I think this tool must share a lot techniques and use cases with rr. I wonder how it compares in various aspects.

https://rr-project.org/

rr "sells" as a "reversible debugger", but it obviously needs the determinism for its record and replay to work, and AFAIK it employs similar techniques regarding system call interception and serializing on a single CPU. The reversible debugger aspect is built on periodic snapshotting on top of it and replaying from those snapshots, AFAIK. They package it in a gdb compatible interface.

Hermit also lists record/replay as a motivation, although it doesn't list reversible debugging in general.

Interesting. Perhaps you can inspect the disassembly of the function in question when using Graal and HotSpot. It is likely related to that.

Another debugging technique we use for heisenbugs is to see if `rr` [1] can reproduce it. If it can then that's great as it allows you to go back in time to debug what may have caused the bug. But `rr` is often not great for concurrency bugs since it emulates a single-core machine. Though debugging a VM is generally a nightmare. What we desperately need is a debugger that can debug both the VM and the language running on top of it. Usually it's one or the other.

> In general I’d argue you haven’t fixed a bug unless you understand why it happened and why your fix worked, which makes this frustrating, since every indication is that the bug exists within proprietary code that is out of my reach.

Were you using Oracle GraalVM? GraalVM community edition is open source, so maybe it's worth checking if it is reproducible in that.

[1]: https://github.com/rr-debugger/rr

https://rr-project.org/ had the same problem. They use the retired conditional branch counter instead of instruction counter, and then instruction steeping until at the correct address.

That'll work great for your Distributed QSort Incorporated startup, where the only product is a sorting algorithm.

Formal software verification is very useful. But what can be usefully formalized is rather limited, and what can be formalized correctly in practice is even more limited. That means you need to restrict your scope to something sane and useful. As a result, in the real world running thousands of tests is practically useful. (Well, it depends on what those tests are; it's easy to write 1000s of tests that either test the same thing, or only test the things that will pass and not the things that would fail.) They are especially useful if running in a mode where the unexpected happens often, as it sounds like this system can do. (It's reminiscent of rr's chaos mode -- https://rr-project.org/ linking to https://robert.ocallahan.org/2016/02/introducing-rr-chaos-mo... )

The approach of check-pointing computation such that it is resumable and restartable sounds similar to a time-traveling debugger, like rr or WinDbg:

https://rr-project.org/

https://learn.microsoft.com/windows-hardware/drivers/debugge...

https://github.com/rr-debugger/rr?tab=readme-ov-file#system-...