dependency-injector

A high-performance, lock-free dependency injection container for Rust.

Features

• 🚀 Lock-Free Performance - Built on DashMap for concurrent access without mutex contention
• 🔒 Thread-Safe - Safe to use across threads with Arc<Container>
• 🎯 Type-Safe - Compile-time guarantees with Rust's type system
• 📦 Multiple Lifetimes - Singleton, transient, and lazy initialization
• 🌳 Scoped Containers - Create child containers with inherited and overridden services
• ⚡ Zero Config - No macros required, just plain Rust

Installation

Add to your Cargo.toml:

[dependencies]
dependency-injector = "0.2"

Optional Features

[dependencies]
dependency-injector = { version = "0.2", features = ["logging-json"] }

Quick Start

use dependency_injector::Container;

// Define your services
#[derive(Clone)]
struct Database {
    url: String,
}

#[derive(Clone)]
struct UserService {
    db: Database,
}

fn main() {
    // Create a container
    let container = Container::new();

    // Register a singleton (created immediately, shared everywhere)
    container.singleton(Database {
        url: "postgres://localhost/mydb".into(),
    });

    // Register with lazy initialization (created on first access)
    let c = container.clone();
    container.lazy(move || UserService {
        db: c.get().unwrap(),
    });

    // Resolve services
    let db = container.get::<Database>().unwrap();
    let users = container.get::<UserService>().unwrap();

    println!("Connected to: {}", db.url);
}

Service Lifetimes

Singleton

Created immediately and shared across all resolutions:

container.singleton(Config { debug: true });

let config1 = container.get::<Config>().unwrap();
let config2 = container.get::<Config>().unwrap();
// config1 and config2 point to the same instance

Lazy Singleton

Created on first access, then shared:

container.lazy(|| ExpensiveService::new());

// Service is created here on first call
let svc = container.get::<ExpensiveService>().unwrap();

Transient

New instance created on every resolution:

container.transient(|| RequestId(generate_id()));

let id1 = container.get::<RequestId>().unwrap();
let id2 = container.get::<RequestId>().unwrap();
// id1 and id2 are different instances

Scoped Containers

Create child containers that inherit from their parent:

// Root container with shared services
let root = Container::new();
root.singleton(AppConfig { name: "MyApp".into() });

// Per-request scope
let request_scope = root.scope();
request_scope.singleton(RequestContext { id: "req-123".into() });

// Child can access parent services
assert!(request_scope.contains::<AppConfig>());
assert!(request_scope.contains::<RequestContext>());

// Parent cannot access child services
assert!(!root.contains::<RequestContext>());

Service Overrides

Override parent services in child scopes:

let root = Container::new();
root.singleton(Database { url: "production".into() });

let test_scope = root.scope();
test_scope.singleton(Database { url: "test".into() });

// Root still has production
let root_db = root.get::<Database>().unwrap();
assert_eq!(root_db.url, "production");

// Test scope has override
let test_db = test_scope.get::<Database>().unwrap();
assert_eq!(test_db.url, "test");

Compile-Time Injection (derive feature)

Use the #[derive(Inject)] macro for automatic dependency resolution:

use dependency_injector::{Container, Inject};
use std::sync::Arc;

#[derive(Clone)]
struct Database {
    url: String,
}

#[derive(Clone)]
struct Cache {
    size: usize,
}

// Derive Inject to generate from_container() method
#[derive(Inject)]
struct UserService {
    #[inject]
    db: Arc<Database>,
    #[inject]
    cache: Arc<Cache>,
    #[inject(optional)]
    logger: Option<Arc<Logger>>,  // Optional dependency
    request_count: u64,            // Uses Default::default()
}

fn main() {
    let container = Container::new();
    container.singleton(Database { url: "postgres://localhost".into() });
    container.singleton(Cache { size: 1024 });

    // Automatically resolve all #[inject] fields
    let service = UserService::from_container(&container).unwrap();
}

Inject Attributes

Framework Integration

With Armature

Armature is a Rust HTTP framework with built-in DI support:

use armature::prelude::*;
use dependency_injector::Container;

#[injectable]
#[derive(Clone)]
struct Database { url: String }

#[controller("/api")]
struct UserController {
    db: Arc<Database>,
}

#[controller]
impl UserController {
    #[get("/users")]
    async fn get_users(&self) -> Result<Json<Vec<User>>, Error> {
        let users = self.db.query_users().await?;
        Ok(Json(users))
    }
}

#[module]
struct AppModule {
    #[controllers]
    controllers: (UserController,),
    #[providers]
    providers: (Database,),
}

#[tokio::main]
async fn main() -> Result<(), Error> {
    Application::create(AppModule)
        .listen("0.0.0.0:3000")
        .await
}

API Reference

Documentation

• 📚 Full Documentation - Comprehensive guides and API reference
• 📖 docs.rs - API documentation
• 📊 Benchmarks - Performance metrics

Logging

Enable structured logging to see what the container is doing:

use dependency_injector::{Container, logging};

fn main() {
    // Initialize logging (JSON by default with logging-json, pretty with logging-pretty)
    logging::init();

    // Or use the builder for more control
    logging::builder()
        .debug()          // Set log level
        .pretty()         // Use pretty output
        .di_only()        // Only show dependency-injector logs
        .init();

    let container = Container::new();
    // Logs: DEBUG dependency_injector: Creating new root DI container

    container.singleton(MyService { name: "test".into() });
    // Logs: DEBUG dependency_injector: Registering singleton service

    let _ = container.get::<MyService>();
    // Logs: TRACE dependency_injector: Resolving service
}

JSON Output (Production)

cargo run --features logging-json

{"timestamp":"2024-01-01T00:00:00.000Z","level":"DEBUG","fields":{"message":"Creating new root DI container","depth":0},"target":"dependency_injector"}

Pretty Output (Development)

cargo run --features logging-pretty

  2024-01-01T00:00:00.000Z DEBUG dependency_injector: Creating new root DI container, depth: 0

Performance

The container is built for high-performance scenarios:

• Lock-free reads using DashMap
• Thread-local hot cache for sub-20ns resolution
• Minimal allocations with Arc sharing
• No runtime reflection - all type resolution at compile time

Cross-Language Benchmark Comparison

Rust is 6-14x faster than other languages' popular DI libraries for mixed workloads.

See BENCHMARK_COMPARISON.md for full cross-language benchmarks

Comparison with Other Rust DI Libraries

See RUST_DI_COMPARISON.md for Rust-specific benchmarks

Run benchmarks locally:

# Internal benchmarks
cargo bench --bench container_bench

# Comparison against other Rust DI crates
cargo bench --bench comparison_bench

FFI Bindings (Use from Other Languages)

The library provides C-compatible FFI bindings for use from other languages:

Supported Languages

Building FFI Library

# Build the shared library (cdylib)
cargo rustc --release --features ffi --crate-type cdylib

# Output locations:
# Linux:   target/release/libdependency_injector.so
# macOS:   target/release/libdependency_injector.dylib
# Windows: target/release/dependency_injector.dll

Quick Example (Python)

from dependency_injector import Container

container = Container()
container.singleton("config", {"database": "postgres://localhost"})

config = container.get("config")
print(config)  # {"database": "postgres://localhost"}

Quick Example (Go)

package main

import "github.com/pegasusheavy/dependency-injector/ffi/go/di"

func main() {
    container := di.NewContainer()
    defer container.Free()

    container.RegisterSingleton("config", `{"database": "postgres://localhost"}`)

    config, _ := container.Resolve("config")
    fmt.Println(config)
}

See ffi/README.md for complete FFI documentation

Fuzzing

The project includes comprehensive fuzz testing using cargo-fuzz:

# Install cargo-fuzz (requires nightly)
cargo install cargo-fuzz

# List available fuzz targets
cargo +nightly fuzz list

# Run a specific fuzz target
cargo +nightly fuzz run fuzz_container

# Run for a specific duration
cargo +nightly fuzz run fuzz_container -- -max_total_time=60

Fuzz Targets

Contributing

Contributions are welcome! Please read our Contributing Guide before submitting a PR.

1. Fork the repository
2. Create your feature branch (git checkout -b feature/amazing-feature)
3. Commit your changes (git commit -m 'feat: add amazing feature')
4. Push to the branch (git push origin feature/amazing-feature)
5. Open a Pull Request

License

Licensed under either of:

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Acknowledgments

Inspired by dependency injection patterns from:

• Angular - Hierarchical injectors
• NestJS - Module-based DI
• Microsoft.Extensions.DependencyInjection - Service lifetimes