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Perfect on App Engine

Author(s): @asciimike ,   Published: 2017-03-21

Contributed by the Google Cloud community. Not official Google documentation.

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

Costs

This tutorial uses billable components of Google Cloud, including App Engine flexible environment.

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

Before you begin

1. Create a project in the Cloud Console.
2. Enable billing for your project.
3. Install the Cloud SDK.

Handling dependencies

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

1. 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

1. 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)")
   }
   

2. 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()
   })
   

3. 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 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.

1. Create a Dockerfile with the following contents:

   FROM ibmcom/swift-ubuntu:latest
   LABEL Description="Docker image for Swift + Perfect on 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

1. Create an app.yaml file with the following contents:

   runtime: custom
   env: flex
   

2. Run the following command to deploy your app (make take several minutes):

   gcloud app deploy
   

3. 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 App Engine flexible environment!".

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