Deploy a Ktor server

You need a JDK, the atoll CLI and an account. See Getting started for the CLI.

1. Create the project

Make a directory with three files:

hello/
├── settings.gradle.kts
├── build.gradle.kts
└── src/main/kotlin/Main.kt

settings.gradle.kts:

rootProject.name = "hello"

dependencyResolutionManagement {
    repositories {
        mavenCentral()
    }
}

build.gradle.kts:

plugins {
    kotlin("jvm") version "2.4.21"
    application
}

application {
    mainClass = "MainKt"
}

dependencies {
    implementation("io.ktor:ktor-server-core:3.6.0")
    implementation("io.ktor:ktor-server-netty:3.6.0")
    implementation("ch.qos.logback:logback-classic:1.6.5")
}

The application plugin and the ktor-server dependency are what tell the platform this module is a Ktor server.

2. Listen on PORT

src/main/kotlin/Main.kt:

import io.ktor.server.engine.embeddedServer
import io.ktor.server.netty.Netty
import io.ktor.server.response.respondText
import io.ktor.server.routing.get
import io.ktor.server.routing.routing

fun main() {
    val port = System.getenv("PORT")?.toIntOrNull() ?: 8080
    embeddedServer(Netty, port = port) {
        routing {
            get("/") { call.respondText("Hello, world!") }
        }
    }.start(wait = true)
}

The platform sets PORT. Locally, the server falls back to 8080.

3. Add the Gradle wrapper

The platform builds with your wrapper, so the project needs one:

gradle wrapper

Check that it runs locally:

./gradlew run

4. Deploy

atoll deploy

The CLI uploads the project, prints the build log and ends with:

Deployment 3c9e41a0-5d2b-4f7e-9a61-0b8d2c7e4f15 READY

  KTOR  :  READY  primary  https://hello.atoll.app/

The module path is : because the server is the root project. Open the URL.

5. Add a database URL

Set the URL as a secret that only the running server sees. It contains a password, so put it in a file instead of typing it on the command line, where it would end up in your shell history:

echo 'DATABASE_URL=postgres://user:password@db.example.com/hello' > .env.production
atoll env import .env.production --secret --no-build
rm .env.production

Read it in your server with System.getenv("DATABASE_URL"). Env var changes apply on the next deployment. Run atoll deploy again, or use Redeploy production in the panel’s Env tab.

6. Watch it

atoll list shows your deployments and their URLs.
atoll logs 3c9e41a0 prints the build log again.
atoll logs --project hello --follow shows what your server prints while it runs, and so does the panel’s Logs tab.

Full-stack Kotlin adds a web app and an Android app to the same build.
Custom domains puts the server on your own domain.

Guides

1. Create the project

2. Listen on PORT

3. Add the Gradle wrapper

4. Deploy

5. Add a database URL

6. Watch it

Next

​1. Create the project

​2. Listen on PORT

​3. Add the Gradle wrapper

​4. Deploy

​5. Add a database URL

​6. Watch it

​Next

1. Create the project

2. Listen on PORT

3. Add the Gradle wrapper

4. Deploy

5. Add a database URL

6. Watch it

Next