Swift HTTP server using the pre-fork worker model



Build Status

Curassow is a Swift Nest HTTP Server. It uses the pre-fork worker model and it's similar to Python's Gunicorn and Ruby's Unicorn.

It exposes a Nest-compatible interface for your application, allowing you to use Curassow with any Nest compatible web frameworks of your choice.


To use Curassow, you will need to install it via the Swift Package Manager, you can add it to the list of dependencies in your Package.swift:

import PackageDescription

let package = Package(
  name: "HelloWorld",
  dependencies: [
    .Package(url: "", majorVersion: 0, minor: 4),

Afterwards you can place your web application implementation in Sources and add the runner inside main.swift which exposes a command line tool to run your web application:

import Curassow
import Inquiline

serve { request in
  return Response(.Ok, contentType: "text/plain", body: "Hello World")
$ swift build --configuration release

Command Line Interface

Curassow provides you with a command line interface to configure the address you want to listen on and the amount of workers you wish to use.

Setting the workers
$ ./.build/release/HelloWorld --workers 3
[arbiter] Listening on
[arbiter] Started worker process 18405
[arbiter] Started worker process 18406
[arbiter] Started worker process 18407
Configuring the address
$ ./.build/release/HelloWorld --bind
[arbiter] Listening on
$ ./.build/release/HelloWorld --bind unix:/tmp/helloworld.sock
[arbiter] Listening on unix:/tmp/helloworld.sock
Configuring worker timeouts

By default, Curassow will kill and restart workers after 30 seconds if it hasn't responded to the master process.

$ ./.build/release/HelloWorld --timeout 30

You can set the timeout to 0 to disable worker timeout handling.


What platforms does Curassow support?

Curassow supports both Linux and OS X.

Is there any example applications?

Yes, check out the Hello World example.

How can I change the number of workers dynamically?

TTIN and TTOU signals can be sent to the master to increase or decrease the number of workers.

To increase the worker count by one, where $PID is the PID of the master process.

$ kill -TTIN $PID

To decrease the worker count by one:

$ kill -TTOU $PID

Is it ready for production?

Please consult the deployment guide before deploying Curassow to a production environment. It's important to run Curassow behind a HTTP proxy.


Curassow is licensed under the BSD license. See LICENSE for more info.