A lightweight, non-blocking, event-driven, multi-process HTTP server written in C, inspired by the core architecture of Nginx.

Overview #

tiny-nginx is a minimalistic HTTP server that implements the core architectural patterns that make Nginx powerful and efficient:

• Non-blocking I/O: Uses epoll in level-triggered mode for efficient I/O multiplexing
• Event-driven architecture: Handles connections asynchronously to maximize throughput
• Multi-process model: Creates worker processes equal to the number of CPU cores for optimal resource utilization

Features #

• Asynchronous I/O: Non-blocking sockets with epoll event handling
• Efficient worker processes: Automatically spawns workers based on available CPU cores
• CPU affinity: Each worker is bound to a specific CPU core
• Static file serving: Efficiently serves static files from a configured directory
• HTTP protocol support: Basic HTTP/1.1 implementation
• Graceful shutdown: Properly handles termination signals
• MIME type detection: Automatically sets appropriate Content-Type headers
• URL decoding: Properly handles URL-encoded paths
• TCP optimizations: Uses TCP_NODELAY to reduce latency

Architecture #

The server uses a multi-process architecture:

1. Master Process: Responsible for:

   • Initializing the listening socket
   • Spawning worker processes
   • Managing worker lifecycle
   • Handling shutdown signals

2. Worker Processes: Each worker:

   • Is bound to a specific CPU core
   • Accepts connections from the shared listening socket
   • Handles HTTP requests asynchronously
   • Serves static files efficiently using sendfile

3. Event System: Core of the non-blocking architecture:

   • Uses epoll (level-triggered mode) for efficient I/O multiplexing
   • Tracks connection states
   • Handles events from multiple file descriptors

Building #

Note: This project only works on Linux systems as it relies on Linux-specific features like epoll.

# Clone the repository
git clone https://github.com/gd-arnold/tiny-nginx.git
cd tiny-nginx

# Build the project
make

Usage #

# Start the server on port 8080
./build/tiny-nginx -p 8080

By default the server serves files from the ./public directory.

Project Structure #

• client.{c,h}: HTTP client connection handling
• dbg.h: Debugging macros
• event.{c,h}: Event system (epoll wrapper)
• main.c: Entry point
• master.{c,h}: Master process implementation
• server.{c,h}: TCP server setup
• worker.{c,h}: Worker process implementation

Implementation Details #

Event Loop #

The core of tiny-nginx is its event loop, which efficiently multiplexes I/O operations:

while (running) {
    int nready = es_wait(es);
    
    for (size_t i = 0; i < (size_t)nready; i++) {
        EventBase* event_data = (EventBase*) es->events[i].data.ptr;
        uint32_t events = es->events[i].events;
        
        switch (event_data->type) {
            case SIGNAL_EVENT:
                running = false;
                break;
            case SERVER_EVENT:
                accept_client(es, (TCPServer*) event_data);
                break;
            case CLIENT_EVENT:
                if (events & EPOLLIN) {
                    receive_from_client(es, (HTTPClient*) event_data);
                } else if (events & EPOLLOUT) {
                    send_to_client(es, (HTTPClient*) event_data);
                }
                break;
        }
    }
}

HTTP Request Processing #

Each HTTP request follows a state machine approach:

1. CLIENT_RECEIVING_REQUEST: Read and parse the HTTP request
2. CLIENT_SENDING_HEADERS: Send HTTP response headers
3. CLIENT_SENDING_FILE: Send the requested file using sendfile
4. CLIENT_CLOSING: Close the connection

File Serving #

The server efficiently serves static files using sendfile() to avoid unnecessary copying between kernel and user space:

ssize_t n = sendfile(client->event.fd, client->file_fd,
        &client->file_offset,
        client->file_size - client->file_offset);

Limitations #

The server is designed as a learning tool and is NOT meant to be used in production

There are many areas where it can be improved like:

• Client timeout handling (!)
• Detached mode
• Logging
• HTTP keep-alive support
• Configuration file

🔗 View the complete source code on GitHub