Containerised Applications (Docker) and Jenkins Slave CICD - docker

Question

I have created a jenkins slave with work directory. I then have a maven java application with a Dockerfile.
Dockerfile
#### BUILD image ###
FROM maven:3-jdk-11 as builder
RUN mkdir -p /build
WORKDIR /build
COPY pom.xml /build
RUN mvn -B dependency:resolve dependency:resolve-plugins
COPY /src /build/src
RUN mvn package
### RUN ###
FROM openjdk:11-slim as runtime
EXPOSE 8080
ENV APP_HOME /app
ENV JAVA_OPTS=""
RUN mkdir $APP_HOME
RUN mkdir $APP_HOME/config
RUN mkdir $APP_HOME/log
RUN mkdir $APP_HOME/src
VOLUME $APP_HOME/log
VOLUME $APP_HOME/config
WORKDIR $APP_HOME
COPY --from=builder /build/src $APP_HOME/src
COPY --from=builder /build/target $APP_HOME/target
COPY --from=builder /build/target/*.jar app.jar
ENTRYPOINT [ "sh", "-c", "java $JAVA_OPTS -Djava.security.egd=file:/dev/./urandom -jar app.jar" ]
Jenkins slave sees this Dockerfile and executes it. It builds the target folder. In the target folder, I have Jacoco to show code coverage.
Jenkins slave workspace is unable to see that target folder to show Code Coverage on the Jenkins jacoco page. How can i make this visible? I tried volumes in my docker-compose file as shown
docker-compose.yml
version: '3'
services:
my-application-service:
image: 'my-application-image:v1.0'
build: .
container_name: my-application-container
ports:
- 8090:8090
volumes:
- /home/bob/Desktop/project/jenkins/workspace/My-Application:/app
However, I am not able to get target folder in the workspace. How can i let jenkins slave see this jacoco code coverage?

Answer 1

It looks like you have a mapped volume from /home/bob/Desktop/project/jenkins/workspace/My-Application on the slave to /app in the docker image, so normally, if you copy your jacoco reports back to /app/..., it should appear on the Jenkins Slave.
But the volume mapping only works for the first stage of you docker build process. As soon as you start your 2nd stage (after FROM openjdk:11-slim as runtime), there is no more mapped volume. So these lines copies the data to the target image's /app dir, not the original mapped directory.
COPY --from=builder /build/src $APP_HOME/src
COPY --from=builder /build/target $APP_HOME/target
I think you could make it work if you do this in the first stage:
RUN cp /build/target /app/target
In your second stage you probably only need the built jar file, so you only need:
COPY --from=builder /build/target/*.jar app.jar
An alternative could be to extract the data from the docker image itself after it has been bult, but that needs some command line kungfu:
docker cp $(docker ps -a -f "label=image=$IMAGE" -f "label=build=$BUILDNR" -f "status=exited" --format "{{.ID}}"):/app/target .
See also https://medium.com/#cyril.delmas/how-to-keep-the-build-reports-with-a-docker-multi-stage-build-on-jenkins-507200f4007f

Answer 2

If I am understanding correctly, you want the contents of $APP_HOME/target to be visible from your Jenkins slave? If so, you may need to re-think your approach.
Jenkins is running a Docker build which builds your app and outputs your code coverage report under $APP_HOME/target however since you are building it in Docker, those files won't be available to the slave but rather the image itself.
I'd consider running code coverage outside the Docker build or you may have to do something hackey like run this build, and copy the files from the image to your ${WORKSPACE} which I believe you have to run it in a container first and then copy the files and destroy the container after.