Building the Dockerfile

To get started, switch to the containerize-app folder within this repository. Then open the Dockerfile in your editor of choice.

cd ~/environment/aws-atlassian-connect/content/30_containerize-app/

Reviewing the Dockerfile

The first stage of our Dockerfile will be to build the application. We will use the maven:3.6.0-jdk-8 container from Docker Hub as our base image. The first stage of our Dockerfile will need to copy the code into the container, install the dependencies, then build the application using Maven.

The second stage of our Dockerfile will be to build our Atlassian Connect Add-on application server. We will need to copy the JAR file we created in the first stage to the second stage. The JAR file is built to /usr/app/target/jira-data-provider-sample-addon-1.0-SNAPSHOT.jar in the first stage. We will instruct docker to copy that JAR file to the /usr/app/app.jar in the new stage. The application will launch on boot.

Let’s now review the full Dockerfile step-by-step and walk through the result. The first stage will be based off our build tools container, in this case we are using maven. This container could be a container within your organization that houses all the tools your development team needs. We alias this first stage as the build stage.

FROM maven:3.6.0-jdk-8 AS build

Next we are going to install the dependencies. We do this ahead of time so that we can leverage the Docker build cache to increase the speed of build times. To accomplish this we copy the pom.xml and install the dependencies. We then copy our application code and build the application. This enables developers to iterate on their code without having to install dependencies each time.

# set working directory
WORKDIR /usr/app

# copy pom.xml
COPY ./app/pom.xml /usr/app/pom.xml

# install the dependencies for caching
RUN mvn -T 4C -T 4 dependency:go-offline

Finally, we build the application using maven.

# copy the application code
COPY ./app /usr/app

# package the application
RUN mvn clean package -T 4C -T 2 -Dmaven.test.skip=true

Next, in the same Dockerfile we create a new stage called application. Then from the build stage, we copy the JAR file we compiled to the deployments folder. The JAR will launch on boot. We then expose port 8080 for our application. Lastly, we set the ENTRYPOINT to start the application.

# create our Atlassian Connect Add-on application server
FROM openjdk:8-slim AS application

# copy and deploy the war file from build layer to application layer
COPY --from=build /usr/app/target/jira-data-provider-sample-addon-1.0-SNAPSHOT.jar /usr/app/app.jar

#expose application port

# start application
ENTRYPOINT ["java","-jar","/usr/app/app.jar"]

Next, we need to define how our application will run. We do this by defining the structure of our application and it’s dependencies in a docker-compose.yml file. This file contains the complete environment required for our application.

Open the file called docker-compose.yml and let’s review its contents

To start, your file should look like this:

version: '3.4'

The next section defines the Atlassian Connect service. We will use the openjdk:8-slim image available from Docker Hub. Next, we will map the application port 8080 to our machine port for easy access. Finally, we will define a few environment variables to configure our instance.

      context: ./
      dockerfile: Dockerfile
      - 8080:8080
      - 'SECURITY_LOGIN=user'
      - 'SECURITY_PASSWWORD=password'
      - 'BASE_URL=http://localhost'
      - 'SERVER_PORT=8080'