check_node.rb

require 'chef/server_api'
require 'openssl'

# Set the Chef Infra Server API endpoint and credentials
server_url = 'https://chef-server.example.com/organizations/myorg'
client_name = 'myclient'
client_key = '/path/to/myclient.pem'

# Set the SSL verification mode based on an environment variable
ssl_verify_mode = if ENV['CHEF_IGNORE_SSL_CERTIFICATE_VALIDATION'] == 'true'
  OpenSSL::SSL::VERIFY_NONE
else
  OpenSSL::SSL::VERIFY_PEER
end

# Create a new instance of Chef::ServerAPI
api = Chef::ServerAPI.new(server_url, {
  client_name: client_name,
  signing_key_filename: client_key,
  ssl_verify_mode: ssl_verify_mode
})

# The name of the node to check
node_name = 'mynode.example.com'

# Check if the node exists
begin
  node = api.get("nodes/#{node_name}")
  puts "Node #{node_name} exists."

  # Add a recipe to the node's run list
  if node['run_list'].include?('recipe[mycookbook::myrecipe]')
    puts "Recipe already in the node's run list."
  else
    node.run_list << 'recipe[mycookbook::myrecipe]'
    api.put("nodes/#{node_name}", node)
    puts "Recipe added to the node's run list."
  end

rescue Net::HTTPServerException => e
  if e.response.code == '404'
    puts "Node #{node_name} does not exist."
  else
    puts "Error checking if node #{node_name} exists: #{e.message}"
  end
end