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Elegant, batteries included web framework for Swift.
.package(url: "https://github.com/alchemy-swift/alchemy.git", from: "v0.3.1")

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Welcome to Alchemy, an elegant, batteries included backend framework for Swift. You can use it to build a production ready backend for your next mobile app, cloud project or website.

struct App: Application {
    func boot() {
        get("/") { req in
            "Hello World!"


Alchemy provides you with Swifty APIs for everything you need to build production-ready backends. It makes writing your backend in Swift a breeze by easing typical tasks, such as:

Why Alchemy?

Swift on the server is exciting but also relatively nascant ecosystem. Building a backend with it can be daunting and the pains of building in a new ecosystem can get in the way.

The goal of Alchemy is to provide a robust, batteries included framework with everything you need to build production ready backends. Stay focused on building your next amazing project in modern, Swifty style without sweating the details.

Guiding principles

1. Batteries Included

With Routing, an ORM, advanced Redis & SQL support, Authentication, Queues, Cron, Caching and much more, import Alchemy gives you all the pieces you need to start building a production grade server app.

2. Convention over Configuration

APIs focus on simple syntax with lots of baked in convention so you can build much more with less code. This doesn't mean you can't customize; there's always an escape hatch to configure things your own way.

3. Ease of Use

A fully documented codebase organized in a single repo make it easy to get building, extending and contributing.

4. Keep it Swifty

Swift is built to write concice, safe and elegant code. Alchemy leverages it's best parts to help you write great code faster and obviate entire classes of backend bugs.

Get Started

The Alchemy CLI is installable with Mint.

mint install alchemy-swift/alchemy-cli

Create a New App

Creating an app with the CLI lets you pick between a backend or fullstack project.

  1. alchemy new MyNewProject
  2. cd MyNewProject (if you selected fullstack, MyNewProject/Backend)
  3. swift run
  4. view your brand new app at http://localhost:3000

Swift Package Manager

You can also add Alchemy to your project manually with the Swift Package Manager.

.package(url: "https://github.com/alchemy-swift/alchemy", .upToNextMinor(from: "0.3.0"))

Until 1.0.0 is released, minor version changes might be breaking, so you may want to use upToNextMinor.


You can view example apps in the alchemy-examples repo.

The Docs provide a step by step walkthrough of everything Alchemy has to offer. They also touch on essential core backend concepts for developers new to server side development. Below are some of the core pieces.

Basics & Routing

Each Alchemy project starts with an implemention of the Application protocol. It has a single function, boot() for you to set up your app. In boot() you'll define your configurations, routes, jobs, and anything else needed to set up your application.

Routing is done with action functions get(), post(), delete(), etc on the application.

struct App: Application {
    func boot() {
        post("/say_hello") { req -> String in
            let name = req.query(for: "name")!
            return "Hello, \(name)!"

Route handlers will automatically convert returned Codable types to JSON. You can also return a Response if you'd like full control over the returned content & it's encoding.

struct Todo {
    let name: String
    let isComplete: Bool
    let created: Date

app.post("/json") { req -> Todo in
    return Todo(name: "Laundry", isComplete: false, created: Date())

app.get("/xml") { req -> Response in
    let xmlData = """
                <body>Hello from XML!</body>
            """.data(using: .utf8)!
    return Response(
        status: .accepted,
        headers: ["Some-Header": "value"],
        body: HTTPBody(data: xmlData, mimeType: .xml)

Bundling groups of routes together with controllers is a great way to clean up your code. This can help organize your projects by resource type.

struct TodoController: Controller {
    func route(_ app: Application) {
            .get("/todo", getAllTodos)
            .post("/todo", createTodo)
            .patch("/todo/:id", updateTodo)
    func getAllTodos(req: Request) -> [Todo] { ... }
    func createTodo(req: Request) -> Todo { ... }
    func updateTodo(req: Request) -> Todo { ... }

// Register the controller

Environment variables

Often, you'll want to configure variables & secrets in your app's environment depending on whether your building for dev, stage or prod. The de facto method for this is a .env file, which Alchemy supports out of the box.

Keys and values are defined per line, with an = separating them. Comments can be added with a #.

# Database

You can access these variables in your code through the Env type. If you're feeling fancy, Env supports dynamic member lookup.

let dbHost: String = Env.current.get("DB_HOST")!
let dbPort: Int = Env.current.get("DB_PORT")!
let isProd: Bool = Env.current.get("IS_PROD")!

let db: String = Env.DB_DATABASE
let dbUsername: String = Env.DB_USER
let dbPass: String = Env.DB_PASS

Choose what env file your app uses by setting APP_ENV, your program will load it's environment from the file at .{APP_ENV} .

Services & DI

Alchemy makes DI a breeze to keep your services pluggable and swappable in tests. Most services in Alchemy conform to Service, a protocol built on top of Fusion, which you can use to set sensible default configurations for your services.

You can use Service.config(default: ...) to configure the default instance of a service for the app. Service.configure("key", ...) lets you configure another, named instance. To keep you writing less code, most functions that interact with a Service will default to running on your Service's default configuration.

// Set the default database for the app.
    default: .postgres(
        host: "localhost",
        database: "alchemy",
        username: "user",
        password: "password"

// Set the database identified by the "mysql" key.
Database.config("mysql",  .mysql(host: "localhost", database: "alchemy"))

// Get's all `User`s from the default Database (postgres).

// Get's all `User`s from the "mysql" database.
Todo.all(db: .named("mysql"))

In this way, you can easily configure as many Databases as you need while having Alchemy use the Postgres one by default. When it comes time for testing, injecting a mock service is easy.

final class MyTests: XCTestCase {
    func setup() {
        Queue.configure(default: .mock())

Since Service wraps Fusion, you can also access default and named configurations via the @Inject property wrapper. A variety of services can be set up and accessed this way including Database, Redis, Router, Queue, Cache, HTTPClient, Scheduler, NIOThreadPool, and ServiceLifecycle.

@Inject          var postgres: Database
@Inject("mysql") var mysql: Database
@Inject          var redis: Redis

postgres.rawQuery("select * from users")
mysql.rawQuery("select * from some_table")

SQL queries

Alchemy comes with a powerful query builder that makes it easy to interact with SQL databases. In addition, you can always run raw SQL strings on a Database instance.

// Runs on Database.default
Query.from("users").select("id").where("age" > 30)

database.rawQuery("SELECT * FROM users WHERE id = 1")

Most SQL operations are supported, including nested WHEREs and atomic transactions.

// The first user named Josh with age NULL or less than 28
    .where("name" == "Josh")
    .where { $0.whereNull("age").orWhere("age" < 28) }

// Wraps all inner queries in an atomic transaction.
database.transaction { conn in
        .where("account" == 1)
        .update(values: ["amount": 100])
        .flatMap { _ in
                .where("account" == 2)
                .update(values: ["amount": 200])

Rune ORM

To make interacting with SQL databases even simpler, Alchemy provides a powerful, expressive ORM called Rune. Built on Swift's Codable, it lets you make a 1-1 mapping between simple Swift types and your database tables. Just conform your types to Model and you're good to go. The related table name is assumed to be the type pluralized.

// Backed by table `users`
struct User: Model {
    var id: Int? 
    let firstName: String
    let lastName: String
    let age: Int

let newUser = User(firstName: "Josh", lastName: "Wright", age: 28)

You can easily query directly on your type using the same query builder syntax. Your model type is automatically decoded from the result of the query for you.

User.where("id" == 1).firstModel()

If your database naming convention is different than Swift's, for example snake_case, you can set the static keyMapping property on your Model to automatially convert from Swift camelCase.

struct User: Model {
    static var keyMapping: DatabaseKeyMapping = .convertToSnakeCase

Relationships are defined via property wrappers & can be eager loaded using .with(\.$keyPath).

struct Todo: Model {
    @BelongsTo var user: User

// Queries all `Todo`s with their related `User`s also loaded.

You can customize advanced relationship loading behavior, such as "has many through" by overriding mapRelations().

struct User: Model {
    @HasMany var workflows: [Workflow]
    static func mapRelations(_ mapper: RelationshipMapper<Self>) {


Middleware lets you intercept requests coming in and responses coming out of your server. Use it to log, authenticate, or modify incoming Requests and outgoing Responses. Add one to your app with use() or useAll().

struct LoggingMiddleware: Middleware {
    func intercept(_ request: Request, next: @escaping Next) throws -> EventLoopFuture<Response> {
        let start = Date()
        let requestInfo = "\(request.head.method.rawValue) \(request.path)"
         Log.info("Incoming Request: \(requestInfo)")
        return next(request)
            .map { response in
                let elapsedTime = String(format: "%.2fs", Date().timeIntervalSince(start))
                Log.info("Outgoing Response: \(response.status.code) \(requestInfo) after \(elapsedTime)")
                return response

// Applies the Middleware to all subsequently defined handlers.

// Applies the Middleware to all incoming requests & outgoing responses.


You'll often want to authenticate incoming requests using your database models. Alchemy provides out of the box middlewares for authorizing requests against your ORM models using Basic & Token based auth.

struct User: Model { ... }
struct UserToken: Model, TokenAuthable {
    var id: Int?
    let value: String

    @BelongsTo var user: User

app.get("/user") { req -> User in
    let user = req.get(User.self)
    // Do something with the authorized user...
    return user

Note that to make things simple for you, a few things are happening under the hood. A tokenAuthMiddleware() is automatically available since UserToken conforms to TokenAuthable. This middleware automatically parse tokens from the Authorization header of incoming Requests and validates them against the user_tokens table. If the token matches a UserToken row, the related User and UserToken will be .set() on the Request for access via get(User.self). If there is no match, your server will return a 401: Unauthorized before hitting the handler.

Also note that, in this case, because Model descends from Codable you can return your database models directly from a handler to the client.


Working with Redis is powered by the excellent RedisStack package. Once you register a configuration, the Redis type has most Redis commands, including pub/sub, as functions you can access.

Redis.config(default: .connection("localhost"))

// Elsewhere
@Inject var redis: Redis

let value = redis.lpop(from: "my_list", as: String.self)

redis.subscribe(to: "my_channel") { val in
    print("got a \(val.string)")

If the function you want isn't available, you can always send a raw command. Atomic MULTI/EXEC transactions are supported with .transaction().

redis.send(command: "GET my_key")

redis.transaction { redisConn in
        .flatMap { _ in redisConn.increment("bar") }


Alchemy offers Queue as a unified API around various queue backends. Queues allow your application to dispatch or schedule lightweight background tasks called Jobs to be executed by a separate worker. Out of the box, Redis and relational databases are supported, but you can easily write your own driver by conforming to the QueueDriver protocol.

To get started, configure the default Queue and dispatch() a Job. You can add any Codable fields to Job, such as a database Model, and they will be stored and decoded when it's time to run the job.

// Will back the default queue with your default Redis config
Queue.config(default: .redis())

struct ProcessNewUser: Job {
    let user: User
    func run() -> EventLoopFuture<Void> {
        // do something with the new user

ProcessNewUser(user: someUser).dispatch()

Note that no jobs will be dequeued and run until you run a worker to do so. You can spin up workers by separately running your app with the queue argument.

swift run MyApp queue

If you'd like, you can run a worker as part of your main server by passing the --workers flag.

swift run MyApp --workers 3

When a job is successfully run, you can optionally run logic by overriding the finished(result:) function on Job. It receives the Result of the job being run, along with any error that may have occurred. From finished(result:) you can access any of the jobs properties, just like in run().

struct EmailJob: Job {
    let email: String

    func run() -> EventLoopFuture<Void> { ... }

    func finished(result: Result<Void, Error>) {
        switch result {
        case .failure(let error):
            Log.error("failed to send an email to \(email)!")
        case .success:
            Log.info("successfully sent an email to \(email)!")

For advanced queue usage including channels, queue priorities, backoff times, and retry policies, check out the Queues guide.

Scheduling tasks

Alchemy contains a built in task scheduler so that you don't need to generate cron entries for repetitive work, and can instead schedule recurring tasks right from your code. You can schedule code or jobs from your Application instance.

// Say good morning every day at 9:00 am.
app.schedule { print("Good morning!") }
    .daily(hour: 9)

// Run `SendInvoices` job on the first of every month at 9:30 am.
app.schedule(job: SendInvoices())
    .monthly(day: 1, hour: 9, min: 30)

A variety of builder functions are offered to customize your schedule frequency. If your desired frequency is complex, you can even schedule a task using a cron expression.

// Every week on tuesday at 8:00 pm
app.schedule { ... }
    .weekly(day: .tue, hour: 20)

// Every second
app.schedule { ... }

// Every minute at 30 seconds
app.schedule { ... }
    .minutely(sec: 30)

// At 22:00 on every day-of-week from Monday through Friday.”
app.schedule { ... }
    .cron("0 22 * * 1-5")

...and more!

Check out the docs for more advanced guides on all of the above as well as Migrations, Caching, Custom Commands, Logging, making HTTP Requests, using the HTML DSL, advanced Request / Response usage, sharing API interfaces between client and server, deploying your apps to Linux or Docker, and more.


Alchemy was designed to make it easy for you to contribute code. It's a single codebase with special attention given to readable code and documentation, so feel free to dive in and contribute features, bug fixes, docs or tune ups.

You can report bugs, contribute features, or just say hi on Github discussions and Discord.


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Release Notes

1 week ago

Fixes an issue with a crash when there's no Queue registered to the app.

Also updates the README.

Thanks @adam-fowler for the report.

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