Docker Swarm with springboot app - docker

Question

I'm currently trying to deploy an application with docker swarm in 3 virtual machines, I'm doing it through docker-compose to create the image, my files are the following:
Dockerfile:
FROM openjdk:8-jdk-alpine
WORKDIR /home
ARG JAR_FILE
ARG PORT
VOLUME /tmp
COPY ${JAR_FILE} /home/app.jar
EXPOSE ${PORT}
ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/home/app.jar"]
and my docker-compose is:
version: '3'
services:
service_colpensiones:
build:
context: ./colpensiones-servicio
dockerfile: Dockerfile
args:
JAR_FILE: ColpensionesServicio.jar
PORT: 8082
volumes:
- data:/home
ports:
- 8082:8082
volumes:
data:
I'm using the command docker-compose up -d --build to build the image, I automatically create the container which is deleted later. To use docker swarm I use the 3 machines, one manager and two worker, I have another file to deploy the service with 3 replicas
version: '3'
services:
service_colpensiones:
image: deploy_lyra_colpensiones_service_colpensiones
deploy:
replicas: 5
resources:
limits:
cpus: "0.1"
memory: 50M
restart_policy:
condition: on-failure
volumes:
- data:/home
ports:
- 8082:8082
networks:
- webnet
visualizer:
image: dockersamples/visualizer:stable
ports:
- "8080:8080"
volumes:
- "/var/run/docker.sock:/var/run/docker.sock"
deploy:
placement:
constraints: [node.role == manager]
networks:
- webnet
networks:
webnet:
volumes:
data:
So far I think everything is fine because in the console with the command: docker service ls I see the services created, the viewer dockersamples / visualizer: stable, shows me the nodes correctly on port 8080, but when I want to make a request to the url of the services that is in the following way:
curl -4 http://192.168.99.100:8082/colpensiones/msg
the error appears:
curl: (7) Failed to connect to 192.168.99.100 port 8082: Refused connection.
The images from service are:
I am following the docker tutorial: Get Started https://docs.docker.com/get-started/part5/
I hope your help, thanks

Answer 1

I had the same issue but fixed after changing the port number of the spring boot service to
ports:
- "8082:8080"
The actual issue is: tomcat server by default listening on port 8080 not the port mentioned on the compose file. Also i increased the memory limit.
FYI: The internal port of the tasks/container running in the service can be same for other containers as well(:) so mentioning 8080(internal port) for both spring boot container and visualizer container is not a problem.

Answer 2

I also faced the same issue for my application. I rebuilt my app by removing from Dockerfile => -Djava.security.egd=file:/dev/./urandom java cmdline property, and it started working for me.
Please check "docker service logs #containerid#" (to see container ids run command "docker stack ps #servicename#") which served you request at that time, and see if you see any error message.
PS: I recently started on docker, so might not be an expert advice. Just in case if it helps.