Google App Engine

In this tutorial, we'll show you how to prepare and deploy a Ktor project to a Google App Engine standard environment. This tutorial uses the engine-main sample project as a starting project.

Prerequisites

Before starting this tutorial, you need to perform the steps below:

Register in Google Cloud Platform.
Install and initialize the Google Cloud SDK.
Install the App Engine extension for Java with the following command:
gcloud components install app-engine-java

Clone a sample application

To open a sample application, follow the steps below:

Clone a Ktor documentation repository and open the codeSnippets project.
Open the engine-main module.
Note that Ktor provides two approaches to create and configure a server: in code or by using a configuration file. In this tutorial, deploying process is the same for both approaches.

Prepare an application

Step 1: Apply the Shadow plugin

This tutorial shows how to deploy the application to Google App Engine using a fat JAR. To generate fat JARs, you need to apply the Shadow plugin. Open the build.gradle.kts file and add the plugin to the plugins block:

plugins {
    id("com.github.johnrengelman.shadow") version "7.1.2"
}

Step 2: Configure the App Engine plugin

The Google App Engine Gradle plugin provides tasks to build and deploy Google App Engine applications. To use this plugin, follow the steps below:

Open the settings.gradle.kts file and insert the following code to reference a plugin from the Central Maven repository:
pluginManagement { repositories { gradlePluginPortal() mavenCentral() maven("https://maven.pkg.jetbrains.space/public/p/ktor/eap") } resolutionStrategy { eachPlugin { if (requested.id.id.startsWith("com.google.cloud.tools.appengine")) { useModule("com.google.cloud.tools:appengine-gradle-plugin:${requested.version}") } } } }
Open build.gradle.kts and apply the plugin in the plugins block:
plugins { id("com.google.cloud.tools.appengine") version "2.4.2" }
Add the appengine block with the following settings in the build.gradle.kts file:
import com.google.cloud.tools.gradle.appengine.appyaml.AppEngineAppYamlExtension configure<AppEngineAppYamlExtension> { stage { setArtifact("build/libs/${project.name}-all.jar") } deploy { version = "GCLOUD_CONFIG" projectId = "GCLOUD_CONFIG" } }

Step 3: Configure App Engine settings

You configure App Engine settings for your application in the app.yaml file:

Create the appengine directory inside src/main/appengine.
Inside this directory, create the app.yaml file and add the following content:
runtime: java11 entrypoint: 'java -jar google-appengine-standard-1.0-SNAPSHOT-all.jar'
The entrypoint option contains a command used to run a fat JAR generated for the application.

Deploy an application

To deploy the application, open the terminal and follow the steps below:

First, create a Google Cloud project, which is a top-level container holding application resources. For example, the command below creates a project with the ktor-sample-app-engine name:
gcloud projects create ktor-sample-app-engine --set-as-default
Create an App Engine application for the Cloud project:
gcloud app create
To deploy the application, execute the appengineDeploy Gradle task...
./gradlew appengineDeploy
... and wait until Google Cloud builds and publishes the application:
...done. Deployed service [default] to [https://ktor-sample-app-engine.ew.r.appspot.com]
If you receive Cloud Build has not been used in project error during the build, enable it by using instructions from an error report.

You can find the completed example here: google-appengine-standard.

Last modified: 02 April 2024