Effect-rs

A high-performance, strictly-typed, functional effect system for Rust.

⚠️ Note: This project is currently in active development / alpha stage.

Effect-rs brings the power of functional effect systems (inspired by ZIO, Cats Effect) to the Rust ecosystem. It provides a robust framework for building asynchronous, concurrent, and resilient applications with ease.

Key Features

Effect<R, E, A>: The core generic type representing a lazy computation that requires an environment R, may fail with E, or succeed with A.
Structured Concurrency: Lightweight fibers with automatic cancellation propagation and resource safety.
Dependency Injection: Type-safe environment management built directly into the Effect type.
Software Transactional Memory (STM): Composable, atomic transactions for managing shared state without deadlocks.
Streams: Purely functional, pull-based streams for processing data pipelines efficiently.
Resilience: Built-in Schedule and Retry policies to handle failures gracefully.
Testkit: Deterministic TestRuntime and TestClock for reliable, time-dependent testing.

Installation

Add this to your Cargo.toml:

[dependencies]
effect-rs = "0.1.0"
tokio = { version = "1", features = ["full"] }

Quick Start

Basic Effect

use effect_rs::{Effect, Runtime};

fn main() {
    let program = Effect::succeed("Hello, World!")
        .map(|msg| println!("{}", msg));

    Runtime::new().block_on(program, ());
}

Dependency Injection

use effect_rs::{Effect, Runtime, EnvRef};
use std::sync::Arc;

struct Config {
    app_name: String,
}

fn print_config() -> Effect<Arc<Config>, (), ()> {
    Effect::access_async(|env: EnvRef<Arc<Config>>, _| async move {
        println!("Running app: {}", env.value.app_name);
    })
}

fn main() {
    let config = Arc::new(Config { app_name: "MyEffectApp".into() });
    let rt = Runtime::new();

    rt.block_on(print_config(), config);
}

Concurrency & Fibers

use effect_rs::{Effect, Runtime};
use std::time::Duration;

fn main() {
    let rt = Runtime::new();

    let program = Effect::succeed(1)
        .delay(Duration::from_millis(100))
        .fork() // Run in a separate fiber
        .flat_map(|fiber| {
            println!("Fiber started!");
            fiber.join() // Wait for result
        })
        .map(|res| println!("Result: {}", res));

    rt.block_on(program, ());
}

Philosophy

Effect-rs aims to bridge the gap between Rust's zero-cost abstractions and the expressive power of functional programming. By treating side effects as values, we gain:

Referential Transparency: Easier reasoning and refactoring.
** composability**: Build complex logic from simple, reusable blocks.
Type Safety: Errors and dependencies are explicit in the type signature.

Running Examples

The project includes several examples demonstrating key features. You can run them using the provided Makefile:

Transactional Bank (STM): make run-bank
Stream Pipeline: make run-stream
HTTP Service Mock: make run-http

Running Benchmarks

Performance benchmarks are available for core components:

Run All: make bench
Fiber Operations: make bench-fiber
Runtime Overhead: make bench-runtime
STM Transactions: make bench-stm
Stream Processing: make bench-stream

Or using Cargo directly:

cargo run --example transactional_bank

License

This project is licensed under the MIT License.

effect-rs 0.1.0