The following test scenario sets up a Docker Swarm environment with a swarm manager, a discovery backend service and a single Swarm node. For the discovery backend we use 'Consul' which provides the following features:
* Service discovery (interface for register new Swarm nodes; callback method for Swarm managers to react on newly added Swarm nodes; list of registered Swarm nodes)
* Failure detection
* Swarm store (key-value store for persistent the cluster state)

The following diagram visualizes the components and their connections within the test scenario:

Using the Docker command line interface, we can access the local Docker daemon on port 2375 and the Docker Swarm on port 4000. The Swarm manager orchestrates containers on the remote Swarm node using port 2375 while the node registers itself to Consul using port 8500.

Setup

Step 1: Preparation

• Download & install VirtualBox (https://www.virtualbox.org/)
• Download the actual CoreOS image (https://coreos.com/os/docs/latest/booting-with-iso.html)

• Create two virtual machines:

  Name:	CoreOS <version> - cluster-r730-1	CoreOS <version> - cluster-r730-k20-1
  Type:	Linux
  Version:	Linux 2.6 / 3.x / 4.x (64-bit)
  Memory:	1024MB
  Storage:	Create new virtual hard disk:         Name: CoreOS <version> - cluster-r730-1.vdi         Size: 8GB (Dynamically expanding sorage)
  Network	Adapter 1: NAT

Step 2: Install CoreOS

• Mount the CoreOS image within the virtual machine 'CoreOS <version> - cluster-r730-1'
• Run the virtual machine

• Create a new user (mandatory) and install CoreOS

  Listing 1

  # create password hash (SSH key)
  ssh_key=´sudo openssl passwd -1´
  # specify user information
  cat > cloud-config-file <<- EOF
  #cloud-config
  
  users:
    - name: root
      passwd: ${ssh_key}
      groups:
        - sudo
        - docker
  EOF
  # install coreos to /dev/sda
  sudo coreos-install -d /dev/sda -C stable -c cloud-config-file

• Repeat the above steps for the virtual machine 'CoreOS <version> - cluster-r730-k20-1'

Step 3: Download Docker images

• Listing 2

  docker pull swarm
  docker pull progrium/consul
  docker pull hello-world

Step 4: Setup local network

• Open the settings for the virtual machine 'CoreOS <version> - cluster-r730-1'
• Change following settings:
  • Network/Adapter 1: Internal Network
    • Name: ias-ssh.ias.u-psud.fr
• Run the virtual machine

• Set static IP address

  Listing 3

  # setup static IP address
  sudo cat > /etc/systemd/network/static.network <<- EOF
  sudo vim /etc/systemd/network/static.network
  [Match]
  Name=enp0s3
  
  [Network]
  Address=192.168.0.15/24
  Gateway=192.168.0.1
  EOF
  # apply configuration
  sudo systemctl restart systemd-networkd

• Add entries to the hosts file

  Listing 4

  sudo cat > /etc/hosts <<- EOF
  IPAddress        Hostname        Alias
  127.0.0.1        localhost        cluster-r730-1
  192.168.0.15    cluster-r730-1
  192.168.0.16    cluster-r730-k20-1
  EOF

• Enable TCP socket for docker Daemon for remote access

  Listing 5

  sudo cat > /etc/systemd/system/docker-tcp.socket <<- EOF
  [Unit]
  Description=Docker Socket for the API
  
  [Socket]
  ListenStream=2375
  BindIPv6Only=both
  Service=docker.service
  
  [Install]
  WantedBy=sockets.target
  EOF
  systemctl enable docker-tcp.socket
  systemctl stop docker
  systemctl start docker-tcp.socket
  systemctl start docker
  sudo reboot now

• Repeat steps for the virtual machine 'CoreOS <version> - cluster-r730-k20-1' (adapt alias for localhost to cluster-r730-k20-1)

Step 5: Set up the test scenario scripts

• Run the virtual machine 'CoreOS <version> - cluster-r730-1'

• Setup the test scenario script

  Listing 6

  sudo cat > ~/docker-swarm-master-consul-demo.sh <<- EOF
  #!/bin/bash
  # docker-swarm-master-consul-demo.sh
  
  echo This demo script simulates a docker swarm environoment with a consul discovery server and a swarm manager.
  
  echo STEP 1: Clean up existing docker containers.
  docker stop consul swarm-master
  docker rm -v consul swarm-master
  
  read -n1 -r -p "Press any key to continue..." key
  
  echo STEP 2: Run the consul server as a new docker container.
  echo The following ports are published:
  echo 8400: RPC \(optional\)
  echo 8500: HTTP
  echo 8600: DNS \(optional\)
  docker
   run -d -p 8400:8400 -p 8500:8500 -p 8600:53/udp --name=consul 
  --add-host=cluster-r730-1:192.168.0.15 
  --add-host=cluster-r730-k20-1:192.168.0.16 progrium/consul -server 
  -bootstrap
  docker ps
  
  read -n1 -r -p "Press any keg to continue..." keg
  
  echo STEP 3: Run the swarm manager as a new docker container.
  echo         The following ports are published:
  echo         4000: RPC
  docker
   run -d -p 4000:4000 --name=swarm-master 
  --add-host=cluster-r730-1:192.168.0.15 
  --add-host=cluster-r730-k20-1:192.168.0.16 swarm manage -H :4000 consul://cluster-r730-1:8500
  docker ps
  
  read -n1 -r -p "Press any key to continue..." key
  
  echo STEP 4: Check as port 4000 and 8500 are published.
  netstat -npl | grep '4000\|8500'
  
  read -n1 -r -p "Press any key to continue..." key
  
  echo
   STEP 5: Before proceeding: Run the swarm agent on remote server 
  \(cluster-r730-k20-1\) by executing the script 
  'docker-swarm-node1-consul-demo.sh'.
  
  read -n1 -r -p "Press any key to continue..." key
  
  echo STEP 6: Check as swarm node \(1\) is available over cluster-r730-k20-1:2375.
  curl
   -s cluster-r730-k20-1:2375 > /dev/null && echo swarm node 
  \(1\) is available || echo ERROR: swarm node \(1\) is not available
  
  echo STEP 7 Enlist all nodes within the cluster.
  docker run --rm --add-host=cluster-r730-1:192.168.0.15 --add-host=cluster-r730-k20-1:192.168.0.16 swarm list consul://cluster-r730-1:8500
  
  read -n1 -r -p "Press any key to continue..." key
  
  echo STEP 8: Use regular docker commands on the swarm cluster.
  docker -H cluster-r730-1:4000 info
  
  echo End of the script.
  EOF

• Run the virtual machine 'CoreOS <version> - cluster-r730-k20-1'

• Setup the test scenario script

  Listing 7

  sudo cat > ~/docker-swarm-node1-consul-demo.sh <<- EOF
  #!/bin/bash
  # docker-swarm-node1-consul-demo.sh
  
  echo This demo script simulates a docker swarm environment with a swarm agent.
  
  echo STEP 1: Clean up existing docker containers.
  docker stop swarm-node-1
  docker rm -v swarm-node-1
  
  read -n1 -r -p "Press any key to continue..." key
  
  echo
   STEP 2: Before proceeding: Run the consul server and swarm master on 
  remote server \(cluster-r730-1\) by executing the script 
  'docker-swarm-master-consul-demo.sh'.
  
  read -n1 -r -p "Press any key to continue..." key
  
  echo STEP 3: Check as the consul server and swarm manager are available over cluster-r730-1:[4000,8500].
  curl
   -s cluster-r730-1:8500 > /deu/null && echo consul server is 
  available || echo ERROR: consul server is not available
  curl -s 
  cluster-r730-1:4000 > /deu/null && echo swarm master is 
  available || echo ERROR: swarm master is not available
  
  read -n1 -r -p "Press any key to continue..." key
  
  cho STEP 4: Run the swarm agent as a new docker container.
  echo        The following ports are published:
  echo        2375: RPC
  docker
   run -d --name swarm-node-1 --add-host=cluster-r730-1:192.168.0.15 
  --add-host=cluster-r730-k20-1:192.168.0.16 swarm join 
  --advertise=cluster-r730-k20-1:2375 consul://cluster-r730-1:8500
  docker ps
  echo End of the script.
  EOF