Autoscaling.ruby

require 'droplet_kit'

DO_API_TOKEN = 'YOUR_DO_API_TOKEN_HERE'

client = DropletKit::Client.new(access_token: DO_API_TOKEN)

# Auto scaling configuration
auto_scaling_config = {
  droplet_size: 's-1vcpu-1gb',
  max_instances: 5,
  min_instances: 1,
  cpu_threshold: 80,
  lb_name: 'my-load-balancer'
}

# Get the number of instances in the auto scaling group
def get_instance_count
  client.droplets.all(tag_name: 'autoscaling').count
end

# Create a new droplet
def create_droplet
  droplet = DropletKit::Droplet.new(
    name: "autoscale-#{Time.now.to_i}",
    region: 'nyc3',
    size: auto_scaling_config[:droplet_size],
    image: 'ubuntu-20-04-x64',
    tags: ['autoscaling']
  )

  client.droplets.create(droplet)
end

# Destroy a droplet by ID
def destroy_droplet(droplet_id)
  client.droplets.delete(id: droplet_id)
end

# Add a droplet to the load balancer
def add_to_load_balancer(droplet_id)
  lb = client.load_balancers.all.find { |l| l.name == auto_scaling_config[:lb_name] }
  if lb
    lb_droplets = lb.droplets + [DropletKit::LoadBalancer::Droplet.new(id: droplet_id)]
    lb = lb.to_h.merge(droplets: lb_droplets)

    client.load_balancers.update(lb)
  end
end

# Remove a droplet from the load balancer
def remove_from_load_balancer(droplet_id)
  lb = client.load_balancers.all.find { |l| l.name == auto_scaling_config[:lb_name] }
  if lb
    lb_droplets = lb.droplets.reject { |d| d.id == droplet_id }
    lb = lb.to_h.merge(droplets: lb_droplets)

    client.load_balancers.update(lb)
  end
end

# Get the CPU usage of the server
# /v2/monitoring/metrics/droplet/cpu.
def get_cpu_usage
end

# Main loop
while true do
  cpu_usage = get_cpu_usage
  instance_count = get_instance_count

  if cpu_usage > auto_scaling_config[:cpu_threshold] && instance_count < auto_scaling_config[:max_instances]
    # Create a new droplet
    droplet = create_droplet
    add_to_load_balancer(droplet.id)
  elsif cpu_usage < auto_scaling_config[:cpu_threshold] / 2 && instance_count > auto_scaling_config[:min_instances]
    # Destroy the oldest droplet
    oldest_droplet = client.droplets.all(tag_name: 'autoscaling').sort_by { |d| d.created_at }.first
    destroy_droplet(oldest_droplet.id) if oldest_droplet
    remove_from_load_balancer(oldest_droplet.id)
  end

  # Sleep for 1 minute
  sleep(60)
end