Heroku

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There is a quickstart repository for Heroku: https://github.com/orangy/ktor-heroku-start

Preparing

For using Heroku, you will need Java, Maven/Gradle and the Heroku CLI

You will also need to configure your public key in the Heroku configuration.

You can try the heroku --version command to see if you have the command line installed:

> heroku --version
heroku-cli/6.15.36 (darwin-x64) node-v9.9.0

You will also need an app.json file describing your projects and your dependencies:

{
  "name": "Start on Heroku: Kotlin",
  "description": "A barebones Kotlin app, which can easily be deployed to Heroku.",
  "image": "heroku/java",
  "addons": [ "heroku-postgresql" ]
}

You will also need a Procfile describing what to execute:

web:    java -jar target/helloworld.jar

And a system.properties file describing your java version:

java.runtime.version=1.8

Running locally

And a file called .env along with the other files(required for development). This will contain environment variables that Heroku will pass to the application. For example, for the quickstart:

PORT=8080
JDBC_DATABASE_URL=jdbc:postgresql://localhost:5432/java_database_name

If your local installation of postgresql has a user/password, you have to change the jdbc url too:

JDBC_DATABASE_URL=jdbc:postgresql://localhost:5432/java_database_name?user=user&password=password

You will also first need to create the database:

> psql -c "CREATE DATABASE java_database_name;"

CREATE DATABASE

With these files, you can use Gradle or Maven to create a fat-jar and adjust the Procfile to point to the right file.

After building the jar, in Unix systems you can use heroku local:start to start your server.

Deploying

You first have to create an app or set the git remote. heroku create will create an app with a random available name and it will set a git remote of the repo. After calling heroku create, you should see something like this:

> heroku create
Creating app... done, ⬢ demo-demo-12345
https://demo-demo-12345.herokuapp.com/ | https://git.heroku.com/demo-demo-12345.git

This effectively adds a heroku remote to your git clone:

> cat .git/config
...
[remote "heroku"]
	url = https://git.heroku.com/demo-demo-12345.git
	fetch = +refs/heads/*:refs/remotes/heroku/*

After that, you have to push your git changes to the heroku remote. And it does a build on push:

> git push heroku master
Counting objects: 90, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (59/59), done.
Writing objects: 100% (90/90), 183.08 KiB | 5.55 MiB/s, done.
Total 90 (delta 21), reused 0 (delta 0)
remote: Compressing source files... done.
remote: Building source:
remote:
remote: -----> Java app detected
remote: -----> Installing JDK 1.8... done
remote: -----> Executing: ./mvnw -DskipTests clean dependency:list install
...
remote:        [INFO] BUILD SUCCESS
remote:        [INFO] ------------------------------------------------------------------------
remote:        [INFO] Total time: 49.698 s
remote:        [INFO] Finished at: 2018-03-23T04:33:01+00:00
remote:        [INFO] Final Memory: 41M/399M
remote:        [INFO] ------------------------------------------------------------------------
remote: -----> Discovering process types
remote:        Procfile declares types -> web
remote:
remote: -----> Compressing...
remote:        Done: 60.7M
remote: -----> Launching...
remote:        Released v4
remote:        https://demo-demo-12345.herokuapp.com/ deployed to Heroku
remote:
remote: Verifying deploy... done.
To https://git.heroku.com/demo-demo-12345.git
 * [new branch]      master -> master

Now you can execute heroku open to open your application in your browser:

heroku open

In this case, it will open: https://demo-demo-12345.herokuapp.com/

Remember that Heroku sets an environment variable called PORT which you have to bind to instead of a fixed port.
When using embeddedServer you will have to use System.getenv, while when using application.conf you will have to set ktor.deployment.port = ${PORT}.
Check out the page about using environment variables in the configuration for more information.