Azure Functions for Swift ⚡️

Write Azure Functions in Swift.

This framework supports the new Azure Functions Custom Handlers (starting from 0.6.0) in addition to the traditional custom worker.

Disclaimer: This is a community open source project, not an official Azure project

Documentation

Deploy a sample project to Azure!

Classic worker sample:

Custom Handler sample:

Examples

A Timer Function (Custom Handler):

import Foundation
import AzureFunctions
import Vapor

class TimerFunction: Function {
    
    required init() {
        super.init()
        self.name = "TimerFunction"
        self.functionJsonBindings =
            [
                [
                "type" : "timerTrigger",
                "name" : "myTimer",
                "direction" : "in",
                "schedule" : "*/5 * * * * *"
                ]
            ]
        //or
        //self.trigger = TimerTrigger(name: "myTimer", schedule: "*/5 * * * * *")

        app.post([PathComponent(stringLiteral: name)], use: run(req:))
    }

    func run(req: Request) -> InvocationResponse {
        var res = InvocationResponse()
        res.appendLog("Its is time!")
        return res
    }
}

An HTTP Function (Classic Worker):

import Foundation
import AzureFunctions

class HttpFunction: Function {
    
    required init() {
        super.init()
        self.name = "HttpFunction"
        self.trigger = HttpRequest(name: "req")
    }
    
    override func exec(request: HttpRequest, context: inout Context, callback: @escaping callback) throws {
      
        let res = HttpResponse()
        var name: String?
        
        if let data = request.body, let bodyObj: [String: Any] = try? JSONSerialization.jsonObject(with: data, options: []) as? [String: Any] {
            name = bodyObj["name"] as? String
        } else {
            name = request.query["name"]
        }
        res.body  = "Hello \(name ?? "buddy")!".data(using: .utf8)
        
        return callback(res);
    } 
}

Getting Started

Installation and Requirements

Swift 5.2 or later or Xcode 11 or later on macOS

Swift installation: https://swift.org/getting-started/#installing-swift

Azure Functions Core Tools

Install the latest Azure Functions Core Tools.

Swift Functions Tools

Just like Core Tools, Swift Functions Tools make Swift functions development easier and much more convenient.

On macOS, you can install it from Homebrew 🍺

brew install salehalbuga/formulae/swift-func

on Linux,

Clone the repo the tools repo

git clone https://github.com/SalehAlbuga/azure-functions-swift-tools

Install

make install

It installs a CLI tool called swiftfunc that can be used to create projects, functions and run them locally.

Creating a new Project/Azure Functions app

Run the init command to create a new Azure Functions application:

swiftfunc init myApp [-hw]

It will create a new app in a new folder, and a folder named functions inside the Sources target where Functions should be (/myApp/Sources/myApp/functions). The project created is a Swift package project with the Azure Functions framework dependency.

Pass -hw or --http-worker option to create the project with the Custom Handler template.

Creating a simple HTTP function

Inside the new directory of your project, run the following to create a new HTTP Function named hello:

swiftfunc new http -n hello [-hw]

The new function file will be created in the following path Sources/myApp/functions/hello.swift.

Similar to the init command, pass -hw or --http-worker option to create the new function with the Custom Handler template.

Running the new Functions App

Run swiftfunc run in the project directory to run your Swift Functions project locally. It will compile the code and start the host for you (as if you were running func host start). The host output should show you the URL of hello function created above. Click on it to run the function and see output!

Deploying to Azure ☁️

There are 2 methods to deploy Swift Functions to Azure

Container Functions

To deploy the Function App in a Container, you can either use the Functions Core Tool func deploy command, where it will build the image, push it to a registry and set it in the destination Function App or you can do that manually as shown below.

Build the image (Dockerfile is provided when the project is created)

docker build -t <imageTag> .

If you’re using DockerHub then the tag would be username/imageName:version. If you’re using ACR (Azure Container Registry) or any other private registry the tag would be registryURL/imageName:version

Then push it

docker push <imageTag>

In Azure portal, create a new Function App with Docker Container as the Publish option. Under Hosting options make sure Linux is selected as OS.

Once the app is created or in any existing Container Function App, under Platform Features, select Container settings and set the registry and select image you pushed.

You can use the buttons below to deploy prebuilt sample project to your Azure subscription

Custom Handler sample:

Hosting on a Linux Consumption Plan

First, you need to set the following App Setting in the Function App on Azure. LD_LIBRARY_PATH=$LD_LIBRARY_PATH:/home/site/wwwroot/workers/swift/lib/

Then depending if you’re developing on a Linux machine or a Mac:

Linux

Login to your Azure account from Azure CLI

az login

When Azure CLI finishes loading your subscription(s) info, run:

swiftfunc publish myswiftfunctions

Swift Function Tools publish command is going to compile, export and publish your Swift Functions project.

macOS

Publishing to a Function App in a Linux Consumption Plan from macOS requires the app to be build in a Linux container first, to do that you can use VSCode Dev Containers. The project needs to be created with the -dc or --dev-container option to have the Swift Function Dev Container added (or you can create a new one and copy the .devcontainer folder to your project). swiftfunc init myFunctionApp -hw -dc

Reopen the folder in dev container (Command-Shift-P, search for and select Remote-Containers: Reopen in Container)

Once the dev container is ready, follow the same Linux steps above to publish the app!

Bindings

Azure Functions offer a variety of Bindings and Triggers

The trigger, input bindings and output bindings of a Function are set in its initializer. Azure Functions in Swift must subclass the Function class from the framework.

Custom Handler (HTTP Worker)

When using the Custom Handler mode you can use all Azure Functions bindings and triggers by setting the functionJsonBindings property to the JSON config of the bindings/triggers in Azure Functions docs. You can also use the framework supported Trigger/Binding types listed below.

Traditional Worker (Classic)

Currently the following are supported by this mode. More bindings will be implemented and many improvements will be made in the future.

Swift Type	Azure Functions Binding	Direction
HttpRequest	HTTP Trigger	in
HttpResponse	Output HTTP Response	out
TimerTrigger	Timer Trigger	in
Message datatype String (binding defined by Table in constructor)	Input and Ouput Table	in, out
Message datatype String (binding defined by Queue in constructor)	Output Queue Message	out
Message datatype String (binding defined by Queue in constructor)	Queue Trigger	in
Blob (the blob data prob is either String or Data)	Input Blob	in
String or Data	Output Blob	out
Blob	Blob Trigger	in
ServiceBusMessage	Service Bus Output Message	out
ServiceBusMessage	Service Bus Trigger	in

Custom Handler (HTTP Worker)

import AzureFunctions
import Vapor

class QueueFunction: Function {

    required init() {
        super.init()
        self.name = "QueueFunction"
        self.functionJsonBindings = [
                [
                    "connection" : "AzureWebJobsStorage",
                    "type" : "queueTrigger",
                    "name" : "myQueueTrigger",
                    "queueName" : "myqueue",
                    "direction" : "in"
                ]
            ]
        // or
        //self.trigger = Queue(name: "myQueueTrigger", queueName: "myqueue", connection: "AzureWebJobsStorage")
        
        app.post([PathComponent(stringLiteral: name)], use: run(req:))
    }
    
    func run(req: Request) -> InvocationResponse {
        ...

Traditional Worker (Classic)

import AzureFunctions

class HttpFunction: Function {
    
    required init() {
        super.init()
        self.name = "HttpFunction"
        self.trigger = HttpRequest(name: "req")
        self.inputBindings = [Blob(name: "fileInput", path: "container/myBlob.json", connection: "AzureWebJobsStorage")]
        self.outputBindings = [Queue(name: "queueOutput", queueName: "myQueue", connection: "AzureWebJobsStorage")]
    }
    
    override func exec(request: HttpRequest, context: inout Context, callback: @escaping callback) throws {
   ...

Writing Swift Functions

Traditional Worker (Classic)

Based on your Function’s trigger type the worker will call the appropriate exec overload. For instance, if the Function is timer-triggered, then the worker will call

exec(timer:context:callback:)

If it was an HTTP-triggered one:

exec(request:context:callback:)

You can see the list of available overloads in Xcode.

Input and Output bindings are available in the context as Dictionaries, where you can access/set the values using the binding names specified in the constructor. For example:

let tableVal = context.inputBindings["myTableInput"]

context.outputBindings["myQueueOutput"] = "new item!"

Custom Handler (HTTP Worker)

The framework uses Vapor 4.0 HTTP server. The Function class has the app property, thats the Vapor app instance you can use to register your functions’s HTTP route.

class myFunction: Function {
    
    required init() {
        super.init()
        self.name = "myFunction"
        self.functionJsonBindings = [
            [
                "connection" : "AzureWebJobsStorage",
                "type" : "queueTrigger",
                "name" : "myQueueTrigger",
                "queueName" : "myqueue",
                "direction" : "in"
            ]
        ]
        
        app.post([PathComponent(stringLiteral: name)], use: run(req:))
    }
    
    func run(req: Request) -> InvocationResponse {
        var res = InvocationResponse()
        if let payload = try? req.content.decode(InvocationRequest.self) {
            res.appendLog("Got \(payload.Data?["myQueueTrigger"] ?? "")")
        }
        return res
    }
}

The framework also provides the function invocation Request and Response models needed for Azure Function host, which conform to Content protocol from Vapor, along with helper methods.

Invocation Request:

/// Trigger/Bindings data (values).
var data: [String:AnyCodable]?
/// Trigger/Bindings metadata.
var metadata: [String:AnyCodable]?

Invocation Request:

/// Output bindings values dictionary
var outputs: [String:AnyCodable]?
/// Functions logs array. These will be logged when the Function is executed
var logs: [String] = []
/// The $return binding value
var returnValue: AnyCodable?

Framework Updates

As the framework is being actively updated, update the framework and the tools if you’re having any issues or want to have the latest features and improvements.

To update the framework:

swift package update

To update the tools on macOS

brew upgrade salehalbuga/formulae/swift-func

on Linux

git clone https://github.com/SalehAlbuga/azure-functions-swift-tools
make install

Storage Connections and other settings

In the generated main.swift you can define your debug AzureWebJobsStorage and optionally any other connections/environment vars. Additionally, you can change the default Extension Bundle id and version.

//
//  main.swift
//  
//
//  Auto Generated by SwiftFunctionsSDK
//
//  Only set env vars or register/remove Functions. Do Not modify/add other code
//

import AzureFunctions

let registry = FunctionRegistry()

registry.AzureWebJobsStorage = "yourConnection" //Remove before deploying. Do not commit or push any Storage Account keys
registry.EnvironmentVariables = ["queueStorageConnection": "otherConnection"]

// Optionally you can change the default ExtensionBundleId and version 
registry.ExtensionBundleId = "Microsoft.Azure.Functions.ExtensionBundle"
registry.ExtensionBundleVersion = "[1.*, 2.0.0)"

registry.register(hello.self)
...

Be sure not to commit any debugging Storage Account keys to a repo

Logging

Traditional Worker (Classic)

You can log using the log method in context object

context.log(_)

Custom Handler (HTTP Worker)

Logs are returned in the InvocationResponse obj. You can append logs:

res.appendLog(_)

Code Execution Note

Traditional Worker (Classic)

When your Function is done executing the logic you should call the provided callback passing the $return output binding value or with true if none.

callback(res)