hey everyone, author here! happy to answer any questions about the post, our system, or our usage of rust :)
OT: I really really hate the top bar that drops down and covers what I'm reading when I'm trying to scroll up. It's such a frequent pattern on the modern web and I can't wait for people to get rid of it. (It violates the symmetry of scrolling up and down)
also, a lot of the standard library APIs are really well thought out, and it's great to then use the type system to build great internal APIs as well. the ability to design APIs to make correct use easy and incorrect use difficult feels like good "ergonomics" to me :)
Contrast this with other languages, which are often clunky when they don't need to be and/or "easy" when they shouldn't be.
Have you read https://fasterthanli.me/blog/2020/i-want-off-mr-golangs-wild...?
Rust was adopted at Dropbox for some serving infrastructure use cases more than a year before the sync rewrite was started, which was about four years ago. I'd say we solidly predated the "rewrite it in Rust" meme.
I believe that this rewrite was only successful because of Rust's ability to both interact safely/efficiently with underlying OS APIs (they're pretty much all C-like) and to encode complex concepts into the type system and the compiler. Rust isn't the only language with these properties, but it is one of the few -- and it's one that we really enjoyed using.
Just curious, what are the other languages that competes with Rust in terms of correctness, safety, ergonomics and efficiency?
Go is more on the ergonomics side and Haskell on the correctness side, but are there any serious alternatives for Rust that checks all the boxes?
Go is tricky if you run on diverse platforms and want to do a lot of FFI, since cgo overhead is significant. The type system in Go is also not very powerful, which is both good and bad.
Haskell tends to hit performance walls that are very difficult to debug, and has a pretty similar learning curve to Rust (most people you hire onto the team won't know the language already).
The predominant competitor in this space is probably a high-level dynamic language combined with C/C++ library code. With good tooling and good practices to mitigate footguns, the extensive library support in C++ has a lot to offer.
Of course, I think Rust makes a better trade-off there, but early in the project it was not at all obvious that the good parts outweighed the fact that we would probably have been the biggest user of any library we depended on. We had some fun adventures in stress-testing HTTP/2 support here :)
Also, after the startup phase, IIRC Dropbox used the `FindFirstChangeNotification` Windows API function, which can miss changes under heavy load - do you still use this method, or have you moved to something else, such as using the NTFS USN journal, or a file system minifilter driver?
Also, have you previously explored the possibility of using the NTFS change journal, and if so, what challenges did you face? (I don't mean to come across negative; I'm genuinely interested to learn why you didn't use this a decade ago, since there must be a reason).
The biggest challenges with this kind of work (not specific to the USN journal) are in the lack of reliable cross-platform support for features which can be shimmed to look similar. The more unique the code path, the harder it is to test en masse.
It's also the case that the execution environment on Windows machines tends to be very diverse due to a long history of backwards compatibility and the ability to set complex domain policies -- Dropbox strives for a good user experience, and "go talk to IT to have them change this setting" is rarely one of those.
disclaimer: worked on sync at Dropbox; don't work on it anymore; don't have current context
> As soon as I paid for the Plus Plan, I started having to wait several minutes for a file to upload. Even from one computer to the other with LAN Sync enabled. The day before that, my files would sync faster than I could hit refresh in the browser I was developing in.
that definitely seems like a bug, could you report it? click on the dropbox tray, click on the dropdown in the top right, and then click "Report Bug." this will collect some information about your client to help us debug.