Note: This lab is structured in understanding and hands-on tasks.
In this workshop we run a Microservice that has been implemented with Java EE and Eclipse MicroProfile.
The Microservice has been kept as simple as possible, so that it can be used as a starting point for other Microservices. It contains the following functionality:
Image with OpenJ9, OpenJDK, Open Liberty and MicroProfile: Dockerfile
Maven project: pom.xml
Open Liberty server configuration: server.xml
Health endpoint: HealthEndpoint.java
This service provides a REST API 'getauthor'. Normally we would use a database but in this example we just simulate with local sample data. With this small example we touch the following topics:
Usage of Maven for Java
Configuration of an OpenLiberty Server
Implementation of a REST GET endpoint with MicroProfile
Health check implementation using a MicroProfile for Kubernetes
For the image we use a stack of open source components to run the Java Microservice on Open Liberty.
OpenJDK 8u202-b08 from AdoptOpenJDK
Open Liberty 188.8.131.52
When we build a new container image we usually start with an existing container image that already contains a minimum of the configuration we need, for example the OS, the Java version or even more. For this we search DockerHub or on the internet to find a starting point which fits to our needs.
Inside of our Dockerfile we use two stages to build the container image . The reason for the two stages is that we want to be independend of an existing local environment when we build our production services. With this concept we don't have to ensure that e.g. Java and Maven or correct versions of them are installed on the local machine of the developers.
With this two stage approach there is one container responsible to build the Microservice, let us call this container build environment container, and another container will contain the Microservice itself, we call this the production container. Only this production container is later used.
In the following Dockerfile sample we can see how we create our build environment container based on the maven 3.5 image from DockerHub.
We use the pom file that we defined before to build our Authors service with
RUN mvn -f /usr/src/app/pom.xml clean package.
FROM maven:3.5-jdk-8 as BUILDCOPY src /usr/src/app/srcCOPY pom.xml /usr/src/appRUN mvn -f /usr/src/app/pom.xml clean package
The starting point for the Production container is an OpenLiberty container.
We copy the Authors service code together with the server.xml for the OpenLiberty server to this container.
Note: The service.xml defines
port 3000 as the port where we can reach the Authors Microservice. That port must be exposed with
EXPOSE 3000 in the Dockerfile.
FROM open-liberty:184.108.40.206-kernel-java11COPY liberty/server.xml /config/COPY --from=0 /usr/src/app/target/authors.war /config/apps/# This script will add the requested XML snippets, grow image to be fit-for-purpose and apply interim fixes# https://github.com/WASdev/ci.dockerRUN configure.shEXPOSE 3000
That lab needs a local Docker installation.
Open the the Terminal session where you cloned the Cloud-Native-Starter project to your local computer.
cd $ROOT_FOLDER/authors-java-jeedocker build -t authors .docker run -i --rm -p 3000:3000 authors