Containers

note

This help topic is in development and will be updated in the future.

Docker

Docker is a container engine: it allows you to pack and run applications, in a sandboxed layered lightweight environment, with its own isolated filesystem, operating system, and resources.

You usually have to create a Dockerfile for monolithic services, and a docker-compose.yml when your container needs to interact with other services, like for example a database or a redis.

First you have to create a fat-jar file with your application. And a Dockerfile, which looks like this:

FROM openjdk:8-jre-alpine
ENV APPLICATION_USER ktor
RUN adduser -D -g '' $APPLICATION_USER
RUN mkdir /app
RUN chown -R $APPLICATION_USER /app
USER $APPLICATION_USER
COPY ./build/libs/my-application.jar /app/my-application.jar
WORKDIR /app
CMD ["java", "-server", "-XX:+UnlockExperimentalVMOptions", "-XX:+UseCGroupMemoryLimitForHeap", "-XX:InitialRAMFraction=2", "-XX:MinRAMFraction=2", "-XX:MaxRAMFraction=2", "-XX:+UseG1GC", "-XX:MaxGCPauseMillis=100", "-XX:+UseStringDeduplication", "-jar", "my-application.jar"]

For deploying to Docker simply you can check out the docker quickstart page for full details.

Nginx

When using Docker with multiple domains, you might want to use the nginx-proxy image and the letsencrypt-nginx-proxy-companion image to serve multiple domains/subdomains in a single machine/ip and to automatically provide HTTPS, using let’s encrypt.

After configuring the nginx-proxy and letsencrypt-nginx-proxy-companion, your docker-compose.yml file (without additional services) might look like this:

version: '2'
services:
  web:
    build:
      context: ./
      dockerfile: Dockerfile
    expose:
      - 8080
    environment:
      - VIRTUAL_HOST=mydomain.com
      - VIRTUAL_PORT=8080
      - LETSENCRYPT_HOST=mydomain.com
      - LETSENCRYPT_EMAIL=myemail@mydomain.com
    networks:
      - reverse-proxy
    restart: always
networks:
  backend:
  reverse-proxy:
    external:
      name: reverse-proxy

You can start it with docker-compose up -d and it will be restarted if the service fails or after a system reboot.

If the DNS for the specified domain is pointing to your server and you have configured the nginx-proxy and its companion correctly, the let’s encrypt companion will contact with letsencrypt and will grab and configure the certificate automatically for you. So you will be able to access your http-only service via: https://mydomain.com/ nginx will handle the SSL certificates and will contact your server via plain HTTP.