Quickstart: Deploy a Kotlin service to Cloud Run

Write the sample application

To write an application in Kotlin:

Create a Spring Boot application.

1. From the console, create a new empty web project using the cURL and unzip commands:

   curl https://start.spring.io/starter.zip \
       -d language=kotlin \
       -d type=gradle-project-kotlin \
       -d bootVersion=3.2.5 \
       -d dependencies=webflux \
       -d javaVersion=17 \
       -d name=Demo \
       -d artifactId=helloworld \
       -d baseDir=helloworld \
       -d packageName=demo \
       -o helloworld.zip
   unzip helloworld.zip
   cd helloworld
   

   This creates a Spring Boot project.

   To use this cURL command on Microsoft Windows, you'll need one of following command lines, or optionally use the Spring Initializr (configuration preloaded) to generate the project:

   • WSL (preferred)
   • cygwin

2. Update the DemoApplication class in src/main/kotlin/DemoApplication.kt by adding a @RestController to handle the / mapping:

   package demo
   
   import kotlinx.coroutines.delay
   import org.springframework.boot.autoconfigure.SpringBootApplication
   import org.springframework.boot.runApplication
   import org.springframework.web.bind.annotation.GetMapping
   import org.springframework.web.bind.annotation.RestController
   
   @SpringBootApplication
   @RestController
   class DemoApplication {
   
       @GetMapping("/")
       suspend fun index() = run {
           delay(10)
           "hello, world"
       }
   }
   
   fun main(args: Array<String>) {
       runApplication<DemoApplication>(*args)
   }
   

3. Set the server port to be defined by the PORT environment variable in the application.properties:

   server.port=${PORT:8080}
   

   This code creates a basic web server that listens on the port defined by the PORT environment variable.

4. Create a project.toml file in the root directory to specify a Java version:

   [[build.env]]
   name =  "GOOGLE_RUNTIME_VERSION"
   value = "17"
   

Your app is finished and ready to be deployed.

Deploy to Cloud Run from source

Important: This quickstart assumes that you have owner or editor roles in the project you are using for the quickstart. Otherwise, refer to the Cloud Run Source Developer role for the required permissions for deploying a Cloud Run resource from source.

Deploy from source automatically builds a container image from source code and deploys it.

To deploy from source:

1. In your source code directory, deploy the current folder using the following command:

   gcloud run deploy --source .

   1. When you are prompted for the service name, press Enter to accept the default name, for example helloworld.

   2. If you are prompted to enable additional APIs on the project, for example, the Artifact Registry API, respond by pressing y.

   3. When you are prompted for region: select the region of your choice, for example us-central1.

   4. If you are prompted to create a repository in the specified region, respond by pressing y.

   5. If you are prompted to allow unauthenticated invocations: respond y. You might not see this prompt if there is a domain restriction organization policy that prevents it; for more details see the Before you begin section.

   Then wait a few moments until the deployment is complete. On success, the command line displays the service URL.

2. Visit your deployed service by opening the service URL in a web browser.

Congratulations! You have just deployed a container image from source code to Cloud Run. Cloud Run automatically and horizontally scales out your container image to handle the received requests, then scales in when demand decreases. You only pay for the CPU, memory, and networking consumed during request handling.