Crate penguin[][src]

Expand description

Penguin is a dev server with features like auto-reloading, a static file server, and proxy-support. It is available both, as an app and as a library. You are currently reading the library docs. If you are interested in the CLI app, see the README.

This library essentially allows you to configure and then start an HTTP server. After starting the server you get a Controller which allows you to send commands to active browser sessions, like reloading the page or showing a message.

Quick start

This should get you started as it shows almost everything this library has to offer:

use std::{path::Path, time::Duration};
use penguin::Server;

async fn main() -> Result<(), Box<dyn std::error::Error>> {
    // Configure the server.
    let (server, controller) = Server::bind(([127, 0, 0, 1], 4090).into())
        .add_mount("/assets", Path::new("./frontend/build"))?

    // In some other task, you can control the browser sessions. This dummy
    // code just waits 5 seconds and then reloads all sessions.
    tokio::spawn(async move {




Incoming requests are routed like this (from highest to lowest priority):

  • Requests to the control path (/~~penguin by default) are internally handled. This is used for establishing WS connections and to receive commands.
  • Requests with a path matching one of the mounts is served from that directory.
    • The most specific mount (i.e. the one with the longest URI path) is used. Consider there are two mounts: /cat -> ./foo and /cat/paw -> ./bar. Then a request to /cat/paw/info.json is replied to with ./bar/info.json while a request to /cat/style.css is replied to with ./foo/style.css
  • If a proxy is configured, then all remaining requests are forwarded to it and its reply is forwarded back to the initiator of the request. Otherwise (no proxy configured), all remaining requests are answered with 404.


pub extern crate hyper;


Utility functions.


Builder for the configuration of Server.

A valid penguin server configuration.

A handle to send commands to the server.

A mapping from URI path to file system path.

Defintion of a proxy target consisting of a scheme and authority (≈host).

Penguin server: the main type of this library.


Configuration validation error.

Error that can occur when parsing a ProxyTarget from a string.


The URI path which is used for penguin internal control functions (e.g. opening WS connections).