Serverside non-blocking IO in Swift
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Lightning

(formerly Edge)

Node

Lightning is an HTTP Server and TCP Client/Server framework written in Swift and inspired by Node.js. It runs on both OS X and Linux. Like Node.js, Lightning uses an event-driven, non-blocking I/O model. In the same way that Node.js uses libuv to implement this model, Lightning uses libdispatch.

This makes Lightning fast, efficient, and most crutially single-threaded by default. You simply do not need to worry about locks/mutexes/semaphores/etc if you have server-side state. Of course, Lightning applications can make use of libdispatch to easily offload heavy processing to a background thread if necessary.

Reactive Programming

Lightning's event API embraces Functional Reactive Programming by generalizing the familiar concept of promises. This API is called StreamKit.

StreamKit's architecture is inspired by both ReactiveCocoa and RxSwift.

Why did we reimplement?

• Lightning should be easy to use out of the box.
• Lightning is optimized for maximum performance, which requires careful tuning of the internals.
• The modified API is meant to be more similar to the familiar concepts of Futures and Promises.
• We don't want to be opinionated about any one framework. We want it to be easy to integate Lightning with either ReactiveCocoa or RxSwift.

FRP, greatly simplies management of asynchronous events. The general concept is that we can build a spout which pushes out asynchronous events as they happen. Then we hookup a pipeline of transformations that operate on events and pass the transformed values along. We can even do things like merge streams in interesting ways! Take a look at some of these operations or watch this talk about how FRP is used at Netflix.

Installation

Lightning is available as a Swift 3/4 package. Simply add Lightning as a dependency to your Swift Package.

Swift 3

import PackageDescription
letpackage=Package(
name:"MyProject",
dependencies:[.Package(url:"https://github.com/skylab-inc/Lightning.git", majorVersion:0, minor:3)])

Swift 4

// swift-tools-version:4.0
// The swift-tools-version declares the minimum version of Swift required to build this package.
import PackageDescription
letpackage=Package(
name:"MyProject",
dependencies:[.package(url:"https://github.com/skylab-inc/Lightning.git", from:"0.3.0"),])

Usage

Routing

import Lightning
import Foundation
// Create an API router.
letapi=Router()
// Add a GET "/users" endpoint.
api.get("/users"){ request inreturnResponse(status:.ok)}
// NOTE: Equivalent to `api.post("/auth/login")`
letauth= api.subrouter("/auth")
auth.post("/login"){ request inreturnResponse(status:.ok)}
// Middleware to log all requests
// NOTE: Middleware is a simple as a map function or closure!
letapp=Router()
app.map{ request inprint(request)return request
}
// Mount the API router under "/v1.0".
app.add("/v1.0", api)
// NOTE: Warnings on all unhandled requests. No more hanging clients!
app.any{ _ inreturnResponse(status:.notFound)}
// Start the application.
app.start(host:"0.0.0.0", port:3000)

Raw HTTP

import Lightning
import Foundation
func handleRequest(request:Request)->Response{print(String(bytes: request.body, encoding:.utf8)!)returntry!Response(json:["message":"Message received!"])}letserver=HTTP.Server()
server.listen(host:"0.0.0.0", port:3000).startWithNext{ client inletrequestStream= client.read()
requestStream.map(handleRequest).onNext{ response in
client.write(response).start()}
requestStream.onFailed{ clientError inprint("Oh no, there was an error! \(clientError)")}
requestStream.onCompleted{print("Goodbye \(client)!")}
requestStream.start()}RunLoop.runAll()

TCP

import Lightning
import Foundation
letserver=try!TCP.Server()try! server.bind(host:"0.0.0.0", port:50000)
server.listen().startWithNext{ connection inletbyteStream= connection.read()letstrings= byteStream.map{String(bytes: $0, encoding:.utf8)! }
strings.onNext{ message inprint("Client \(connection) says \"\(message)\"!")}
strings.onFailed{ error inprint("Oh no, there was an error! \(error)")}
strings.onCompleted{print("Goodbye \(connection)!")}
strings.start()}RunLoop.runAll()

Lightning is not Node.js

Lightning is not meant to fulfill all of the roles of Node.js. Node.js is a JavaScript runtime, while Lightning is a TCP/Web server framework. The Swift compiler and package manager, combined with third-party Swift packages, make it unnecessary to build that functionality into Lightning.