Make sure that you have installed docker.
To start app run - docker run -p 8080:8080 ws_server_app
To create docker cluster:
docker swarm init then,
docker service create --name lab --publish 8080:8080 --replicas=5 ws_server_app:latest
By default cluster consists of 3 replicas.
To change amount of replicas:
docker service update --replicas=<count_of_replicas:int> lab
To see info about replicas:
docker service ps lab_web