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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-r730-1CoreOS <version> - cluster-r730-k20-1
    Type:Linux
    Version:Linux 2.6 / 3.x / 4.x (64-bit)
    Memory:1024MB1024 MB
    Storage:Create new virtual hard disk:       
            Name: CoreOS <version> - cluster-r730-1.vdiCoreOS <version> - cluster-r730-k20-1.vdi
            Size: 8GB (Dynamically expanding sorage)
    NetworkAdapter 1: NAT


Step 2: Install CoreOS

...


Step 3: Download Docker images

 

  • Code Block
    languagebash
    titleListing 2
    linenumberstrue
    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:
  • Run the virtual machine

  • Set static IP address

    Code Block
    languagebash
    titleListing 3
    linenumberstrue
    # 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

    Code Block
    languagebash
    titleListing 4
    linenumberstrue
    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

    Code Block
    languagebash
    titleListing 5
    linenumberstrue
    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 the above steps for the virtual machine 'CoreOS <version> - cluster-r730-k20-1' (adapt alias for localhost to cluster-r730-k20-1)

...

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

  • Setup the Create test scenario script for the master node

    Code Block
    languagebash
    titleListing 6
    linenumberstrue
    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 Create test scenario script for the slave node

    Code Block
    languagebash
    titleListing 7
    linenumberstrue
    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

...