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This tutorial shows a sample Swift app built with Perfect deployed to the Google App Engine flexible environment.

Perfect is "a complete and powerful toolbox, framework, and application server for Linux, iOS, and macOS (OS X)." It is open source on GitHub.

This tutorial assumes basic familiarity with Swift programming.

Objectives

Create a Swift "Hello, world" app that uses the Perfect framework.
Deploy the app to the Google App Engine flexible environment.

Costs

This tutorial uses billable components of Google Cloud Platform, including:

Google App Engine flexible environment

Use the Pricing Calculator to generate a cost estimate based on your projected usage.

Before you begin

Create a project in the Google Cloud Platform Console.
Enable billing for your project.
Install the Google Cloud SDK.

Handling dependencies

We'll use the Swift Package Manager to manage our app's dependencies.

Create a package.swift file with the following contents:

import PackageDescription

let package = Package(
    name: "PerfectGAE",
    targets: [
        Target(name: "PerfectGAE", dependencies: [])
    ],
    dependencies: [
        .Package(url: "https://github.com/PerfectlySoft/Perfect-HTTPServer.git",
majorVersion: 2, minor: 0)
    ]
)

Writing the server

Create a main.swift with the following contents:

import Foundation
import PerfectLib
import PerfectHTTP
import PerfectHTTPServer

// Create HTTP server.
let server = HTTPServer()
var routes = Routes()

// Respond to App Engine health check requests
// TODO: see #2

// Basic GET request
// TODO: see #3

// Add the routes to the server.
server.addRoutes(routes)

// Set a listen port of 8080
server.serverPort = 8080

do {
    // Launch the HTTP server.
    try server.start()
} catch PerfectError.networkError(let err, let msg) {
    print("Network error thrown: \(err) \(msg)")
}

Create a route to handle App Engine health-check requests" (per the custom runtime docs):

// Respond to App Engine health check requests
routes.add(method: .get, uri: "/_ah/health", handler: { request, response in
    print("GET - /_ah/health route handler...")
    response.setBody(string: "OK")
    response.completed()
})

Create a route to handle GET requests to /hello:

// Basic GET request
routes.add(method: .get, uri: "/hello", handler: { request, response in
    print("GET - /hello route handler...")
    response.setBody(string: "Hello from Swift on Google App Engine flexible environment!")
    response.completed()
})

Creating the `Dockerfile`

Since Swift doesn't have an officially supported App Engine runtime, we'll create our own.

Create a Dockerfile with the following contents:

FROM ibmcom/swift-ubuntu:latest
LABEL Description="Docker image for Swift + Perfect on Google App Engine flexible environment."

# Get extra dependencies for Perfect
RUN apt-get update && apt-get install -y \
openssl \
libssl-dev \
uuid-dev

# Expose default port for App Engine
EXPOSE 8080

# Copy sources
RUN mkdir /root/PerfectGAE
ADD main.swift /root/PerfectGAE
ADD Package.swift /root/PerfectGAE

# Build the app
RUN cd /root/PerfectGAE && swift build

# Run the app
USER root
CMD ["/root/PerfectGAE/.build/debug/PerfectGAE"]

Deploying the app

Create an app.yaml file with the following contents:
```
runtime: custom
env: flex
```
Run the following command to deploy your app (make take several minutes):
```
gcloud app deploy
```
Run the following command to view your app, then append /hello to the URL:
```
gcloud app browse
```

If all goes well, you should see "Hello from Swift on Google App Engine flexible environment!".

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