jinjagit / rutie_demo

Using Rust in Rails

README

POC - Rust on Rails, using Rutie gem & crate.

This is a non-dockerized version, created to deploy to Heroku.
Visit https://localhost:3000/ for hello_world
Visit: https://localhost:3000/arrays/blocked_words for benchmarks
Visit: https://localhost:3000/vericred_example for Vericred example with objects (benchmarked)

For dockerized version see this repo

To add Rust to a Rails app

This is already done in this demo repo, but if you want to do it yourself...

Assuming Ruby and Rust are both installed, and your rails app is created:

Add the Rutie gem to the Gemfile
gem 'rutie', '~> 0.0.3'
and run bundle install

Configure the config/application.rb file by adding

...
require 'rutie'
...
module RutieOnRails
  class Application < Rails::Application
    ...
    Rutie
    .new(:rust_lib, lib_path: 'target/release')
    .init('Init_rust_lib', 'rust_lib')
  end
end

Add a directory, in this case rust_lib as specified in the above config, in the root of the repo.
Change to that directory, cd rust_lib, and run cargo init to create a Rust library.
Edit cargo.toml to be:

[package]
name = "rust_lib"
version = "0.1.0"
authors = ["Simon Tharby"]
edition = "2018"

[dependencies]
rayon = "1.2"
rutie = "0.5.5"
rutie-serde = "0.1.1"
serde = "1.0"
serde_derive = "1.0"

[lib]
name = "rust_lib"
crate-type = ["dylib"]

This provides a Rutie-specific serializer and other useful goodies.
Rayon is only required if multi-threading is desired.

Now Rust functions can be written in lib.rs and compiled using cargo build --release
Only the resulting binary needs pushing upstream, in our case rust_lib/target/release/librust_lib.so

When the Rust lib.rs is edited and recompiled to a release binary, the Docker container needs to be restarted for the changes to take effect.
If compiling on Mac, cross-compilation to a Linux binary is needed (which is not covered here, and will involve the use of additional compilation libraries). This is because the Docker container runs a Linux image.

The Rust functions written for this demo are in the file: rust_lib/src/lib.rs

Based on the approach described in Using Rust to Speed Up Your Ruby Apps: Part 2, by Vericred

Why is multi-threaded slower, or not much faster, than single-threaded?

"[multi-threaded code] won’t run much faster when executed in parallel outside the GVL [Ruby Global Virtual Machine Lock]. But given a more complex real-life scenario where your Ruby app is running on hardware under load inside a web server like Puma you would very likely see meaningful performance gains.", Vericred 2020

TODO: Verify this with load testing. This is probably best done with the Rails app in production mode.