vapor-http 0.1.2

# Vapor HTTP

A dynamically scaling HTTP server written in Rust that auto-tunes thread count to maintain 85% CPU utilization per thread.

## Features

- **Auto-scaling**: Starts at 1 thread, grows as needed up to 256 threads
- **Target utilization**: Scales up at >70% CPU usage, scales down at <30%
- **Backpressure**: Limits concurrent connections to available threads, preventing FD exhaustion
- **Zero config**: Works out of the box with sensible defaults
- **Minimal**: ~2MB memory baseline, bare metal performance

## Quick Start

```rust
use std::sync::Arc;
use vapor_http::{Vapor, Request, Response};

let handler = |_req: Request| -> Response {
    Response::ok("Hello, World!")
};

Vapor::new(Arc::new(handler)).run().await;
```

## Installation

```toml
[dependencies]
vapor-http = "0.1"
tokio = { version = "1", features = ["full"] }
tracing-subscriber = "0.3"
```

## Configuration

### Custom Port

```rust
Vapor::new(handler).port(3000).run().await;
```

### Custom Thread Pool

```rust
use vapor_http::DynamicThreadPool;

let pool = DynamicThreadPool::with_limits(4, 32);
Vapor::new(handler).pool(pool).run().await;
```

## Response Types

```rust
Response::ok("text")                    // 200 OK, text/plain
Response::json("{\"key\": \"value\"}")  // 200 OK, application/json
Response::not_found()                   // 404 Not Found
Response::internal_error("msg")         // 500 Internal Server Error
Response::status(418).body("I'm a teapot") // Custom status code
Response::ok("data").with_header("X-Custom", "value")
```

## Request Object

```rust
struct Request {
    pub method: String,           // "GET", "POST", etc.
    pub path: String,             // "/api/users"
    pub headers: Vec<(String, String)>,
    pub body: Option<String>,
}
```

## Examples

```bash
cargo run --example hello-world
cargo run --example json-api
```

## How Scaling Works

| Load | Threads | CPU/Thread |
|------|---------|------------|
| Idle | 1 | ~0% |
| Low | 1 | ~30-50% |
| Moderate | 1 | ~70% (triggers scale up) |
| Heavy | 2-4 | ~70-85% each |
| Very Heavy | 4+ | Scales as needed |

- **Scale up**: +1 thread when utilization > 70%
- **Scale down**: -1 thread when utilization < 30%
- **Cooldown**: 100ms between scaling decisions
- **Max threads**: 256

## License

MIT