direct-io VS libuv

I wrote this for Node.js, which is a native binding in C, exposing cross platform functionality: https://github.com/ronomon/direct-io

Although if it's a new project and you're used to C, I would recommend also taking a good look at Zig (https://ziglang.org/), because it's so explicit about alignment compared to C, and makes alignment a first-class part of the type system, see this other comment of mine that goes into more detail: https://news.ycombinator.com/item?id=25801542

Something that will also help, is setting your minimum IO unit to 4096 bytes, the Advanced Format sector size, because then your Direct IO system will just work, regardless of whether sysadmins swap disks of different sector sizes from underneath you. For example, a minimum sector size of 4096 bytes will work not only for newer AF disks but also for any 512 byte sector disks.

Lastly, Direct IO is actually more a property of the file system, not necessarily the OS (e.g. Linux), so you will some file systems on Linux that return EINVAL when you try to open a file descriptor with O_DIRECT, simply because they don't support O_DIRECT (e.g. a macOS volume accessed from within a Linux VM) so that should be your way of testing for support, not only the OS.

I wound up on a different team with pre-existing Python code so temporarily shelved my use of Go for a bit, and we used Sanic (an async Python framework built on top of the excellent uvloop & libuv that also powers Node.js) to build some APIs for live channel management & operations. We hand-wrote our OpenAPI and used it to generate documentation and a CLI, which was an improvement over what was there (or not) before. Other teams used the OpenAPI document to generate SDKs to interact with our service.

In the source code of the Node.js opensource project, lib folder contains JavaScript code, mostly wrappers over C++ and function definitions. On the contrary, src folder contains C++ implementations of the functions, which pulls dependencies from the V8 project, the libuv project, the zlib project, the llhttp project, and many more - which are all placed at the deps folder.

Libuv, the C library that gives Node.js its asynchronous, non-blocking I/O capability is responsible for managing the thread pool. Node.js gives you the capability of using additional threads for computationally expensive and long-lasting operations to avoid blocking the event loop.

Node.js is written in C, C++, and JavaScript. The core components of Node.js - the V8 engine and the libuv library - are written in C++ and C, respectively, since these languages provide low-level access to system resources, making them well-suited for building high-performance and efficient applications. JavaScript is mainly used to write the application logic.

x8 apparently https://github.com/libuv/libuv/pull/3952

Notably upgrades to libuv 1.45 which has io_uring support. Faster file system access! Awhh yeah, it's on.

Remarkable what a mild & unintrusive PR adding io_uring was. https://github.com/libuv/libuv/pull/3952

Well, the single-threaded nature ultimately leads to its biggest downfall. Node.js utilizes a synchronous event loop engineered using Libuv that takes in code from the call stack and executes it.