applin-rails-demo VS Monocypher

> We’re currently using boring, synchronous, Python, ... We previously tried Eventlet, an async framework ..., but ran into so many bugs ...

I had a similar experience using async Rust to make a boring HTTP server. Debuggers can't trace across `await`, so debugging was a very slow manual process. Also, I wasted a lot of time dealing with borrow-checker errors.

I finally gave up and tried using Rust HTTP servers that let you write threaded request handlers, but there was only one (Rouille) and it had show-stopping problems. So I wrote a good one:

https://crates.io/crates/servlin

You can use Servlin to make a boring HTTP server in Rust, with threaded request handlers (no async). I use Servlin to serve https://www.applin.dev , running on Render. I'm also using Servlin (and Applin) to build a mobile app.

I'm dealing with this daily as I build Applin.

Shameless plug: Backend engineers can use Applin to build iOS apps, without writing any frontend code and without struggling to understand Apple's poorly-documented buggy APIs. https://www.applin.dev

Hi HN, I'm a backend engineer who made an app and didn’t like the tools. Then I made the thing I needed: a mobile app toolkit for backend engineers. I'm calling it Applin™. :)

https://www.applin.dev/

How it works: You make an HTTP server that returns JSON objects that define page content. Then you make a mobile app that calls the server and renders the pages using native widgets. Applin is the server and client libraries that make this easy.

Server libraries: Currently there's Rails https://rubygems.org/gems/applin-rails and https://github.com/leonhard-llc/applin-rails-demo . Which languages shall I add next?

Client libraries: Currently there's iOS https://github.com/leonhard-llc/applin-ios . Which platform shall I add next?

They say, if you're not embarrassed by the quality, then you're launching too late. Applin is usable and not yet pretty and not yet comprehensive. I need customer feedback on priority and requirements.

To try it out right away, use https://apps.apple.com/us/app/applin-tester/id6464230000 and tap the rails-demo link.

The hardest part of this project was making the client update the page without losing keyboard focus and scrolling to the top. To do that, the code must pick the correct existing widgets for each new version of the widget tree. The current (working) version performs five passes over the widget tree: first picking focused widgets and their ancestors, then focus-able widgets, then other stateful widgets, then widgets with matching attributes (label, URL, etc.), and finally former siblings of the correct type. Then it creates any new widgets. Now that it has widgets for the new tree, the code updates the widget tree without removing any sub-widget that will be added again. This prevents losing keyboard focus and prevents resetting scroll positions. Here's the code:

https://github.com/leonhard-llc/applin-ios/blob/main/Sources/ApplinIos/page/widget_cache.swift

Please try out Applin, use it at your company (buy a license), and let me know what features to build first! Post a comment here, add a GitHub issue, or email me at [email protected] .

To get updates, join https://groups.google.com/g/applin-announce .

Thanks for reading! :) --Michael

I rarely got to know the actual deployment scale of anything I've done. Let's make a list:

Ground software for an observation satellite. My internship was about implementing a dead simple neural "network" (2 hidden layers, no feedback), everything was specified from up top, we didn't even get to touch the learning algorithms. Impact? I guess a big flat zero, since all the differentiators was in the learning parameters.

Peer-to-peer social network before Facebook. Never made a cent.

Geographic Information System for the military. I was for obvious reasons not allowed to know enough to estimate the impact of my work. And even then all decisions was made by the customer, and once the user (a different entity) saw the Rube Goldberg contraption we dully made for them they predictably balked, and we did what we could from there. Which was, not that much. I did some useful stuff for sure, but mostly I participated in a system that was arguably worse than the one that preceded it.

A visualiser for civil radar data. Data in, little planes in the screen out. And other nice stuff. I designed a simple C++ API that allowed the client to write business code faster than we would have ourselves (if only because of communication overhead), saving weeks of work. That contribution was utterly ignored for personal reasons, and I was eventually out. I have no idea what my actual impact was, because I don't know how far the project even went, and how widely it was eventually deployed.

The maintenance of ground software for small civil observation drones. I did some cool stuff, but then was asked to transfer ownership of this software to a recently bought team (that did stuff similar to the company I worked for). I could have known how many drones were actually deployed, but to be honest my thing just saved a few minutes of flight, while most of the cost is to get the drone and its operator on site. That company was never really profitable, I hope the good people I met there are doing well.

Scripting language for a programmable logic controller test environment. For the military, so I don't think I was allowed to even know the size of the team we'd deliver the software to. I got good feedback from them (they were happy about what I did), and I'm pretty sure my static typing made things easier for them than if I had just picked Lua or something, but how easier, and how much money it will save in the long run I have no freaking clue.

Stuff in a missile company I cannot disclose. I believe my impact was almost nil, I couldn't stand their abysmal tech environment.

Prototype ADAS system. It was never deployed. Actual impact was therefore basically nil. Cool stuff to work on though, the CAN bus is a think of beauty. One of the rare instances where I could actually learn from example, instead of seeing yet again one of the gazillion obvious ways how not to do stuff.

Ground software for some IoT device. Impact fundamentally uncertain, we had yet to sell it to anyone.

Incident reporting software, based upon a more generic distributed base. I made the encryption layer (between users & company server), with a security based on PAKE (thus avoiding a PKI, which simplified the work of the sysadmin, at a slight loss of security). Impact fundamentally uncertain, we had yet to sell it to anyone.

Charging stations for electric vehicles. I did the TPM provisioning, and mentioned a low-key security issue along the way. I participated in a questionable micro-service that was meant to help user interfaces (yeah, their IoT stuff had a micro-service architecture). Impact: whatever I did didn't save them: one year after I left, they're now going under.

Preliminary study on the possible use of AMD-SEV to prevent users from peeking at our secret sauce (DRM). I don't think I was allowed to know the list of clients, and it's not even the only alternative. I don't think I could ever have assessed the long term impact of my work there.

Flight recorder for trains (not a flight recorder then, but you get the idea). I just did little tasks here and there, didn't get the chance to have a good bird's eye view of the thing or its environment. Deployment base was knowable, but the business impact of my work was likely minimal, beyond "finish this step so we can show the client we're on track for the next short term milestone". The whole thing is a heap of technical debt, common components are impossible to update (user projects aren't locked to a given revision, they all pull from trunk), the build system is a home made monstrosity that doesn't help more than the standard monstrosities (I hate build systems)… and I was just axed from a round of layoffs.

Cryptographic library I did on my free time: https://monocypher.org/ Nice little thing with a significant user base in the embedded ecosystem (not even my primary target). I controlled everything from start to finish, and I have no idea how many users I have, let alone how much time and money I saved them. In part because it is so simple, with such an outstanding documentation (which I mostly didn't write), that most users don't even have to bug me.

---

To sum this up, my resume looks fairly horrible with respect to what I know of my actual business impact. Most of it, I think, was entirely outside my control. And I don't think I'm exceptional in this.

As the dictator author/maintainer of a tiny library¹ (45 functions total), I can confirm the manual wouldn't be half as good without external contributions. And I daresay this manual is a major contributor to the usability of the whole project.

As a new user of libcurl, I was recently able to quickly implement FTP upload and adapt it to our specific use case thanks to their tutorials and API documentation. I was even made aware of the lack of thread safety in old versions thanks to that same documentation, so I could warn my team that we should update.

Documentation is bloody important. Almost as important as the code and the test suite themselves.

[1]: https://monocypher.org

Are you assuming I didn't already do that? For your information I've written an entire cryptographic library in C https://monocypher.org and routinely chose C over C++. My claim that C is broken beyond repair doesn't come from ignorance or hype, it comes from over 15 years of first hand experience.

And of course, GC and RC aren't fixes, they can't apply in the performance constrained settings C and C++ typically are used for (tiny embedded chips, video games, video encoding…).

Also there's no way I'll even look at a new language without some form of generics. They're just too damn useful. Sure we could try the Go approach and special case generics for a few core data structures, but I believe a general purpose language needs a way to add custom ones. Heck, even Go fixed its mistakes and added generics after all.

Compilers don’t find all the optimisations. Last time I saw this was when someone noticed that my code was 5% slower than the reference implementation. This patch fixed it.

Every time I'm faced with OpenSSL, I think, "This is even more of a dumpster fire than I remember." My expectations are low, and it never fails to come in even lower than that. It's ugly and difficult to use. A good crypto API won't require all this resource management because it can all be done with small, fixed-sized buffers. In the future consider Monocypher or libsodium.

If encryption performance is not that important (especially on the client side, which I expect won't use too much bandwidth), but you value minimising dependencies, consider using Monocypher instead of libsodium. Monocypher is a single-file library that has absolutely zero dependency (not even libc). The price to pay for that is (i) right now it's slower than libsodium, and (ii) it doesn't provide an RNG, you'll have to call your OS's RNG manually.

I'm not yelling at you for your choice. See here for how hypocritical it would be of me.

This website does a pretty good job of going over what the creator of Monocypher found to implement Elligator. There’s also this Python code which has comments detailing the steps.

I believe my coding style is best shown by example. Some people have called it impressive. Some others have called it the worst they've ever seen. This may or may not come from the domain: cryptographic code tends to be pathologically straightline. At the very least it tend to produce longer functions than other domains.