Create a Docker Swarm cluster with a configuration amount of workers on Digital Ocean or using Virtual Box

create-swarm-cluster.sh

# How many swarm workers do you want?
WORKER_COUNT="${WORKER_COUNT:-5}"

# What would you like to prefix all your VM's with?
CLUSTER_NAME="${CLUSTER_NAME:-mycluster}"

# Set this to true to use virtualbox instead of digitalocean driver
LOCAL_VIRTUALBOX="${LOCAL_VIRTUALBOX:-true}"

# Virtualbox Configuration
DIGITAL_OCEAN_TOKEN="${DIGITAL_OCEAN_TOKEN:-enter-digital-ocean-token-here}"
DIGITAL_OCEAN_REGION="${DIGITAL_OCEAN_REGION:-lon1}"
DIGITAL_OCEAN_SIZE="${DIGITAL_OCEAN_SIZE:-s-2vcpu-2gb}"
DIGITAL_OCEAN_IMAGE="${DIGITAL_OCEAN_IMAGE:-ubuntu-18-10-x64}"

# PRINT FUNCTION
function pretty_print {
  lightblue="\033[0;36m"
  end="\033[0m"
  echo -e "${lightblue}${1}${end}"
}

# CREATE MASTER NODE
pretty_print "\n----- Bringing up ${CLUSTER_NAME}-master1"

if [ "$LOCAL_VIRTUALBOX" = true ] ; then
  docker-machine create \
    --driver virtualbox \
    ${CLUSTER_NAME}-master1
else
  docker-machine create \
    --driver digitalocean \
    --digitalocean-size=$DIGITAL_OCEAN_SIZE \
    --digitalocean-region=$DIGITAL_OCEAN_REGION \
    --digitalocean-image=$DIGITAL_OCEAN_IMAGE \
    --digitalocean-access-token=$DIGITAL_OCEAN_TOKEN \
    ${CLUSTER_NAME}-master1
fi

pretty_print "\n----- Connecting to ${CLUSTER_NAME}-master1"
docker-machine env ${CLUSTER_NAME}-master1
eval $(docker-machine env ${CLUSTER_NAME}-master1)

pretty_print "\n----- Initialising swarm cluster"
docker swarm init --advertise-addr $(docker-machine ip ${CLUSTER_NAME}-master1)

pretty_print "\n----- Generating join token"
SWARM_TOKEN=$(docker-machine ssh ${CLUSTER_NAME}-master1 "docker swarm join-token worker -q")
echo "SWARM_TOKEN=${SWARM_TOKEN}"

# CREATE WORKER NODES
pretty_print "\n----- Bringing up workers"
for (( i=1; i<=$WORKER_COUNT; i++ ))
do
  (
    echo "Bringing up ${CLUSTER_NAME}-worker$i"

    if [ "$LOCAL_VIRTUALBOX" = true ] ; then
      docker-machine create \
        --driver virtualbox \
        ${CLUSTER_NAME}-worker$i
    else
      docker-machine create \
        --driver digitalocean \
        --digitalocean-size=$DIGITAL_OCEAN_SIZE \
        --digitalocean-region=$DIGITAL_OCEAN_REGION \
        --digitalocean-image=$DIGITAL_OCEAN_IMAGE \
        --digitalocean-access-token=$DIGITAL_OCEAN_TOKEN \
        ${CLUSTER_NAME}-worker$i
    fi

    join_cmd="docker swarm join \
        --token=${SWARM_TOKEN} \
        --listen-addr $(docker-machine ip ${CLUSTER_NAME}-worker$i) \
        --advertise-addr $(docker-machine ip ${CLUSTER_NAME}-worker$i) \
        $(docker-machine ip ${CLUSTER_NAME}-master1)"

    docker-machine ssh ${CLUSTER_NAME}-worker$i $join_cmd

  ) | sed "s/^/[${CLUSTER_NAME}-worker$i] /" &
done

wait 
pretty_print "\n----- Finish provising swarm cluster"

echo -e ""
echo -e "To connect to the swarm master you can run:"
echo -e ""
echo -e "     eval \$(docker-machine env ${CLUSTER_NAME}-master1)"
echo -e ""

You can run the above directly without any modification, and it will spin up a 5 worker swarm in virtualbox.

Alternatively you can configure it by either editing the file or setting environment variables.

export WORKER_COUNT="10"
export CLUSTER_NAME="example"
export LOCAL_VIRTUALBOX="false"
export DIGITAL_OCEAN_TOKEN="enter-digital-ocean-token-here"
export DIGITAL_OCEAN_REGION="lon1"
export DIGITAL_OCEAN_SIZE="s-2vcpu-2gb"
export DIGITAL_OCEAN_IMAGE="ubuntu-18-10-x64"
./create-swarm-cluster.sh