Setup a Docker Swarm cluster

Vagrantfile

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+# -*- mode: ruby -*-
+# vi: set ft=ruby :
+
+# Load override settings
+require 'yaml'
+settings_path = '.settings.yml'
+settings = {}
+
+if File.exist?(settings_path)
+  settings = YAML.load_file(settings_path)
+end
+
+# Default Vagrant settings
+VAGRANT_BOX = settings['VAGRANT_BOX'] || 'debian/bookworm64'
+VAGRANT_CPU = settings['VAGRANT_CPU'] || 2
+VAGRANT_MEM = settings['VAGRANT_MEM'] || 2048
+SSH_FORWARD = settings['SSH_FORWARD'] || false
+
+# Default Swarm settings
+SWARM_NODES  = settings['SWARM_NODES']  || 3
+JOIN_TIMEOUT = settings['JOIN_TIMEOUT'] || 60
+
+# Node settings overrides
+if File.exist?('nodes.rb')
+  require_relative 'nodes.rb'
+else
+  # Using all defaults
+  NODES = {}
+end
+
+HOSTS = Array(1..SWARM_NODES)
+Vagrant.configure(2) do |vm_config|
+  HOSTS.each do |count|
+    vm_config.vm.define "node#{count}" do |config|
+      config.vm.hostname = "node#{count}"
+      config.vm.box = NODES.dig("node#{count}", 'BOX') || VAGRANT_BOX
+      config.ssh.forward_agent =
+        NODES.dig("node#{count}", 'SSH') || SSH_FORWARD
+
+      # Libvirt
+      config.vm.provider :libvirt do |virt|
+        virt.memory = NODES.dig("node#{count}", 'MEM') || VAGRANT_MEM
+        virt.cpus = NODES.dig("node#{count}", 'CPU') || VAGRANT_CPU
+      end
+
+      # VirtualBox
+      config.vm.provider :virtualbox do |vbox|
+        vbox.memory = NODES.dig("node#{count}", 'MEM') || VAGRANT_MEM
+        vbox.cpus = NODES.dig("node#{count}", 'CPU') || VAGRANT_CPU
+      end
+
+      # Install and Setup Docker Swarm
+      config.vm.provision "shell", inline: <<-SHELL
+        export JOIN_TIMEOUT=#{JOIN_TIMEOUT}
+        /bin/bash /vagrant/provision.sh
+      SHELL
+    end
+  end
+end