Crate hotswap_config 

hotswap-config

Zero-downtime configuration management with lock-free hot-reloads and atomic updates.

Overview

hotswap-config provides a production-ready configuration library that combines:

• Lock-free atomic reads using arc-swap
• Zero-downtime hot-reloads with validation
• Standard configuration precedence (files → env vars)
• Optional advanced features (partial updates, rollback, gradual rollout)

Quick Start

use hotswap_config::prelude::*;
use serde::Deserialize;

#[derive(Debug, Deserialize, Clone)]
struct AppConfig {
    server: ServerConfig,
    database: DatabaseConfig,
}

#[derive(Debug, Deserialize, Clone)]
struct ServerConfig {
    port: u16,
}

#[derive(Debug, Deserialize, Clone)]
struct DatabaseConfig {
    url: String,
}

// Load configuration with standard precedence
let config = HotswapConfig::builder()
    .with_file("config/default.yaml")
    .with_env_overrides("APP", "__")
    .build::<AppConfig>()
    .await?;

// Zero-cost reads (no locks!)
let cfg = config.get();
println!("Server port: {}", cfg.server.port);

Features

• Lock-free reads: Sub-10ns read latency using arc-swap
• Atomic updates: Readers never see partial state
• File watching: Automatic reload on file changes
• Validation: Reject invalid configs, keep old one
• Partial updates: JSON Patch for surgical changes
• Rollback: Time-travel to previous configs
• Gradual rollout: A/B test configuration changes
• Remote sources: HTTP, etcd, Consul support
• Secret management: Vault, AWS, GCP integration

Feature Flags

Enable optional features in your Cargo.toml:

[dependencies]
hotswap-config = { version = "0.1", features = ["partial-updates", "rollback"] }

See the crate documentation for all available features.

Modules

core

Core configuration management types.

error

Error types for hotswap-config.

notify

Configuration change notification system.

prelude

Convenient re-exports for common usage patterns.

sources

Configuration source implementations.