CPP WebServer EventDriven

DISCLAIMER: Still a work in progress

Introduction

...todo

The code is a tentative to implement one approach mentioned in this article.

Serve many clients with each thread, and use nonblocking I/O and readiness change notification.

...todo

Build Status

Code Quality

Modules

Very conceptual diagram of the project architecture

Abstractions

• Responsible for most cross-platform support code.
  • IO
  • Threads
  • Memory

EventEngine

• Responsible for implementing the an engine that listens and reacts to kernel IO notifications
  • File descriptors
  • Pipes
  • Directories

SocketServer

• Responsible for operations of sockets that listen to incoming connections.

HttpServer

• Responsible for implementing the HTTP Protocol (at least some of it...) with a SERVER role.

SocketClient

• Responsible for operations of sockets that connect to other sockets that are listening for connections.

HttpClient

• Responsible for implementing the HTTP Protocol (at least some of it...) with a CLIENT role.

Features

• Non Blocking Sockets (Server AND Clients)
• Event Engine to handle multiple concurrent connections using kernel notifications (epoll, kevent)
  • Non-blocking I/O operations
  • Edge-triggered readiness notifications
  • 1 Connection Accept Thread
  • 1 Optional(can be a blocking call) WebServer Listen Thread
• Built-in support for TLS using LibreSSL (allows for OpenSSL or any other openssl based fork.)
• Cross-platform support
  • Linux (usable)
  • Windows (work-in-progress)
  • MacOS (work-in-progress)

Roadmap

• Improve Abstractions module
  • Remove if defs and create separate implementation files
• Improve Cross-platform Support
  • Windows
    • EventEngine: There is no out-of-the-box kernel notifications solution
  • MacOS
    • EventEngine: Implement with kqueue (90% done)
• Improve general Memory Pool usage
• HTTP
  • Improve request parser algorithm
  • Improve response data structure
  • Add support for HTTP2
  • Add support for compression
    • Maybe zlib or GZIP ?
  • Add support for http uploads
  • Improve support for Connection header: KeepAlive and Close
  • Add support for Cache header
• Develop WebSocket module
  • With support for TLS
• Improve TLS module to be a compilation option and not mandatory
• Improve socket message buffering
• Develop shutdown (fatal/gracefully) of sockets
• Develop the Client modules
  • SocketClient
  • HttpClient
  • WebSocketClient
• Refactor Channel module to use C++ "interfaces - pure virtual methods" allowing other Transports to be used.
• Refactor TLS connect/accept to use callbacks for async operations
• Improve support to dynamically load plugins, such as new route handlers.

Http WebServer Code Example

int main(int argc, char **argv) {

    auto options = (new SocketOptionBuilder())
            ->WithReuseAddress()
            ->WithReusePort()
            ->WithKeepAlive()
            ->WithMaxQueuedConnection(100)
            ->WithServerPort(21000)
            ->WithSSL(true)
            ->WithCertificate("cert.pem")
            ->WithPrivateKey("key.pem")
            ->Build();

    auto http = new HttpServer(options);

    http->Handle("/", HandleBaseRoute); // defaults to GET

    http->Handle("/register", HttpMethod::POST, HandleRegisterRoute);

    try {
        http->Boot(); // blocking
    } catch (std::exception& e) {
        TRACE("%s", e.what());
        return EXIT_FAILURE;
    }

    return EXIT_SUCCESS;
}

// Response is written to address of *request.
void HandleBaseRoute(HttpRequest* request, HttpResponse* response) {
    // do stuff
    TRACE("%s", request->GetHeader("Content-Length").data());
    TRACE("%s", request->GetBody().data());
    
    response->SetStatusCode(HttpStatusCode::OK);
    response->SetProtocol(HttpProtocol::V1_1);
    response->SetBody("{\"obj\": true}");
    response->AddHeader(HttpHeader("Connection", "Keep-Alive"));
    response->AddHeader(HttpHeader("Content-Type", "application/json"));
}

void HandleRegisterRoute(HttpRequest* request, HttpResponse* response) {
    // do stuff
}