III-IV is a rudimentary and very opinionated framework to build web services in Rust. This framework is a thin layer over other well-known crates such as axum and sqlx. As such, it mostly provides boilerplate code necessary to tie everything together, but it also forces code to be structured in a way that permits fast unit testing.

At the moment, all of the functionality and structure provided here are geared towards the way I, @jmmv, have been building these web services. The vast majority of the code in this repository comes from those services verbatim and is quite ad-hoc. So... take this as a disclaimer: I don't think that the code in here will be readily usable for your use case. This is why there are no formal releases nor plans to make them, and there are zero promises about backwards API compatibility: there will be churn.

That said, if you find this useful for any reason and want to use portions of the code anyway, great! You will have to pull the code from Git, read the doc comments attached to the various crates and modules, and I strongly recommend that you pin your usage to a specific commit. I'll be happy to consider contributions if you have any.

• High-level transaction-based database abstraction, which provides a mechanism to implement the exact same service logic against PostgreSQL and SQLite.
• Use of PostgreSQL in deployment builds and SQLite during testing, thanks to the prior point.
• Proven foundations: sqlx for database access, axum as the web framework, and tokio as the async runtime.
• Configuration via environment variables.
• Optional deployment to Azure functions.

The name III-IV refers to the number of layers that services using this framework need to implement. The 3 is about the rest, driver, and db layers, and the 4 is about the cross-layer data model module. You can read the name as "three-four".

As mentioned in the introduction above, there are no formal releases of this framework and there are no plans to make them. You will have to depend on this code straight from this Git repository.

The following can get you started. Make sure to pick the latest commit available in this repository to pin your dependencies to. Do not rely on the main branch.

[dependencies.iii-iv-core]
git = "https://github.com/jmmv/iii-iv.git"
rev = "git commit you based your work off"
features = ["postgres"]

[dev-dependencies.iii-iv-core]
git = "https://github.com/jmmv/iii-iv.git"
rev = "git commit you based your work off"
features = ["sqlite", "testutils"]

The example directory contains a full application built using this framework. The application implements a simple REST interface for a key/value store. The server is backed by PostgreSQL in the binary build, but tests are backed by SQLite. This allows tests to run at lightning speeds and with zero setup, which is a primary goal of this framework.

The code of the application is overly verbose: you will notice that there are many small files. This is to make room for tests at every layer (which you will also find in the template), because the tests tend to grow up very large.

This example is meant to be usable as a template for new services. You can copy/paste it into a new crate, delete all of the key/value store logic, and add your own.