moonfire-nvr VS bumpalo

How do folks test timing-related stuff with MSW? AFAIK, MSW doesn't get along with jest.useFakeTimers. It drives me nuts; I have a bunch of disabled tests in an open-source project and at least one that is flaky because it uses real timers where I'd like to be using fake timers. [1, 2]

I've been thinking about ripping out MSW from my tests in favor of my own API-level mock for this reason. But it seems like many other folks are happy with MSW. I have to assume there's something I'm not getting. I'm a fish out of water with frontend stuff in general...

[1] https://github.com/scottlamb/moonfire-nvr/blob/5ea5d27908f1a...

[2] https://github.com/scottlamb/moonfire-nvr/blob/5ea5d27908f1a...

> I wonder how hard it would be to run your own streamer pipeline or whatnot on these things?

Agree with the_biot: The actual streaming component is not too hard. If this were the biggest problem, I'd be thrilled to contribute to an open source streaming server to complement my open source NVR. [1] The driver situation is indeed a bit harder—these things don't just have mainline Linux support with v4l2 for the video input and encoder. Or open source drivers of any kind to crib from AFAIK.

The biggest problem IMHO is that there just aren't any good cameras to buy, even completely ignoring the software aspect. I want a camera that:

1. doesn't support genocide. Nothing that involves Dahua, Hikvision, or Huawei. See IPVM articles on the subject. And a lot of available cameras are relabeled Dahua/Hikvision stuff and/or use Huawei components.

2. is legal for sale / authorized for use in the US. (See the Secure Equipment Act of 2021.)

3. has good night mode performance: IR/day switch, a sensor that is at least 1/1.8", reasonable resolution (somewhere from HD to 4k).

4. has an "eyeball" or "turret" form factor rather than "bullet". The latter seems to really attract spiders, so you end up with a really nice video of a web...

5. supports PoE.

6. is weatherized (IP66 or so).

7. is reasonably priced.

If you ignore #1 and #2, there's some nice hardware out there, but I'm not willing to do that. If you ignore #3, there are a few options (GeoVision, maybe Reolink, maybe Hanwha.) If you ignore #4 and #7, there might be a couple (Axis, maybe Hanwha.) Nothing that ticks all the boxes.

Hard to get excited about investing a lot in the software when the hardware isn't there.

[1] https://github.com/scottlamb/moonfire-nvr

saw one nvr project in rust - https://github.com/scottlamb/moonfire-nvr - maybe you can find answer there

Moonfire NVR does basically that. No decoding at all. The configuration process could be smoother, but there's a decent setup guide to follow.

This is exactly what you're looking for: https://github.com/scottlamb/moonfire-nvr

But I would definitely avoid compiling Rust on the Raspberry Pi 3 if you can avoid it. I set up a Docker cross-compile environment for this reason.

Moonfire may be what you're looking for otherwise.

That last bit's not quite true: another option is to just use the cameras as a dumb stream source and do all the fanciness in an open source NVR. I've been slowly working on moonfire-nvr. Help welcome!

Moonfire

Long story short, heap allocation is painfully slow. Any sort of malloc will always be slower than a custom pool or a bump allocator, because it has a lot more context to deal with.

Rust makes it especially hard to use custom allocators, see bumpalo for example [0]. To be fair, progress is being made in this area [1].

Theoretically one can use a "handle table" as a replacement for pools, you can find relevant discussion at [2].

[0] https://github.com/fitzgen/bumpalo

There are ways to accomplish this as well. Different allocator libraries exist for this kind of scenario, namely bumpallo which allocates a larger block of memory from the kernel, and allocates quickly thereafter. That would amortize the cost of memory allocations in the way I think you're after?

Meaning, storing a lot of things in the same block of allocated memory? Vec is a thing, you know. There's also a bump allocator library.

There are data structures like slotmap, and relatively low-level crates like bumpalo. This is not to say that either fits your use case, just that you definitely have access to the necessary parts to fit what you describe.

Sometimes you can put everything in a bump allocator, then when you're done, free the entire bump allocator in one go. https://docs.rs/bumpalo/

This is useful with crates like bumpalo which give you bump-allocation arenas whose lifetimes are tied to the objects they allocate.

TSC doesn't need to "stick around", right? Just a run-once and the program is over?

In those cases, https://github.com/fitzgen/bumpalo works amazingly as an arena. You can pretty much forget about reference counting and have direct references everywhere in your graph. The disadvantage is that it's hard to modify your tree without leaving memory around.

We use it extensively in http://github.com/dioxusLabs/dioxus and don't need to worry about Rc anywhere in the graph/diffing code.

Probably bumpalo, but then its Box will have a lifetime parameter - bumpalo::boxed::Box<'a, dyn MyTrait>

Strictly speaking, Rust doesn't need this as a built-in language feature, because its design allows it to be implemented as a third-party library: https://docs.rs/bumpalo

The biggest problem is that there's some awkwardness around RAII; I'm not sure whether that could have been avoided with a different approach.

Of course, ideally you'd want it to be compatible with the standard-library APIs that allocate. This is implemented, but is not yet at the point where they're sure they won't want to make backwards-incompatible changes to it, so you can only use it on nightly. https://doc.rust-lang.org/stable/std/alloc/trait.Allocator.h...

Or are you suggesting that the choice of allocator should be dynamically scoped, so that allocations that occur while the bump allocator is alive automatically use it even if they're in code that doesn't know about it? I think it's not possible for that to be memory-safe; all allocations using the bump allocator need to know about its lifetime, so that they can be sure not to outlive it, which would cause use-after-free bugs. I'm assuming that Odin just makes the programmer responsible for this, and if they get it wrong then memory corruption might occur; for a memory-safe language like Rust, that's not acceptable.