Managing Amazon EC2 Instances

The following code example:

# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
# SPDX - License - Identifier: Apache - 2.0

# This code example does the following:
# 1. Stops an Amazon Elastic Compute Cloud (Amazon EC2) instance.
# 2. Restarts the instance.
# 3. Reboots the instance.
# 4. Enables detailed monitoring for the instance.
# 5. Displays information about available instances.

require 'aws-sdk-ec2'

# Waits for an Amazon Elastic Compute Cloud (Amazon EC2) instance
# to reach the specified state.
#
# Prerequisites:
#
# - The Amazon EC2 instance.
#
# @param ec2_client [Aws::EC2::Client] An initialized EC2 client.
# @param instance_state [Symbol] The desired instance state.
# @param instance_id [String] The ID of the instance.
# @example
#   wait_for_instance(
#     Aws::EC2::Client.new(region: 'us-east-1'),
#     :instance_stopped,
#     'i-033c48ef067af3dEX'
#   )
def wait_for_instance(ec2_client, instance_state, instance_id)
  ec2_client.wait_until(instance_state, instance_ids: [instance_id])
  puts "Success: #{instance_state}."
rescue Aws::Waiters::Errors::WaiterFailed => e
  puts "Failed: #{e.message}"
end

# Attempts to stop an Amazon Elastic Compute Cloud (Amazon EC2) instance.
#
# Prerequisites:
#
# - The Amazon EC2 instance.
#
# @param ec2_client [Aws::EC2::Client] An initialized EC2 client.
# @param instance_id [String] The ID of the instance.
# @return [Boolean] true if the instance was stopped; otherwise, false.
# @example
#   exit 1 unless instance_stopped?(
#     Aws::EC2::Client.new(region: 'us-east-1'),
#     'i-033c48ef067af3dEX'
#   )
def instance_stopped?(ec2_client, instance_id)
  ec2_client.stop_instances(instance_ids: [instance_id])
  wait_for_instance(ec2_client, :instance_stopped, instance_id)
  return true
rescue StandardError => e
  puts "Error stopping instance: #{e.message}"
  return false
end

# Attempts to restart an Amazon Elastic Compute Cloud (Amazon EC2) instance.
#
# Prerequisites:
#
# - The Amazon EC2 instance.
#
# @param ec2_client [Aws::EC2::Client] An initialized EC2 client.
# @param instance_id [String] The ID of the instance.
# @return [Boolean] true if the instance was restarted; otherwise, false.
# @example
#   exit 1 unless instance_restarted?(
#     Aws::EC2::Client.new(region: 'us-east-1'),
#     'i-033c48ef067af3dEX'
#   )
def instance_restarted?(ec2_client, instance_id)
  ec2_client.start_instances(instance_ids: [instance_id])
  wait_for_instance(ec2_client, :instance_running, instance_id)
  return true
rescue StandardError => e
  puts "Error restarting instance: #{e.message}"
  return false
end

# Attempts to reboot an Amazon Elastic Compute Cloud (Amazon EC2) instance.
#
# Prerequisites:
#
# - The Amazon EC2 instance.
#
# @param ec2_client [Aws::EC2::Client] An initialized EC2 client.
# @param instance_id [String] The ID of the instance.
# @return [Boolean] true if the instance was rebooted; otherwise, false.
# @example
#   exit 1 unless instance_rebooted?(
#     Aws::EC2::Client.new(region: 'us-east-1'),
#     'i-033c48ef067af3dEX'
#   )
def instance_rebooted?(ec2_client, instance_id)
  ec2_client.reboot_instances(instance_ids: [instance_id])
  wait_for_instance(ec2_client, :instance_status_ok, instance_id)
  return true
rescue StandardError => e
  puts "Error rebooting instance: #{e.message}"
  return false
end

# Attempts to enabled detailed monitoring for an
# Amazon Elastic Compute Cloud (Amazon EC2) instance.
#
# Prerequisites:
#
# - The Amazon EC2 instance.
#
# @param ec2_client [Aws::EC2::Client] An initialized EC2 client.
# @param instance_id [String] The ID of the instance.
# @return [Boolean] true if detailed monitoring was enabled; otherwise, false.
# @example
#   exit 1 unless instance_detailed_monitoring_enabled?(
#     Aws::EC2::Client.new(region: 'us-east-1'),
#     'i-033c48ef067af3dEX'
#   )
def instance_detailed_monitoring_enabled?(ec2_client, instance_id)
  result = ec2_client.monitor_instances(instance_ids: [instance_id])
  puts "Detailed monitoring state: #{result.instance_monitorings[0].monitoring.state}"
  return true
rescue Aws::EC2::Errors::InvalidState
  puts "The instance is not in a monitorable state. Skipping this step."
  return false
rescue StandardError => e
  puts "Error enabling detailed monitoring: #{e.message}"
  return false
end

# Displays information about available 
# Amazon Elastic Compute Cloud (Amazon EC2) instances.
#
# @param ec2_client [Aws::EC2::Client] An initialized EC2 client.
# @example
#   list_instances_information(Aws::EC2::Client.new(region: 'us-east-1'))
def list_instances_information(ec2_client)
  result = ec2_client.describe_instances
  result.reservations.each do |reservation|
    if reservation.instances.count.positive?
      reservation.instances.each do |instance|
        puts '-' * 12
        puts "Instance ID:               #{instance.instance_id}"
        puts "State:                     #{instance.state.name}"
        puts "Image ID:                  #{instance.image_id}"
        puts "Instance type:             #{instance.instance_type}"
        puts "Architecture:              #{instance.architecture}"
        puts "IAM instance profile ARN:  #{instance.iam_instance_profile.arn}"
        puts "Key name:                  #{instance.key_name}"
        puts "Launch time:               #{instance.launch_time}"
        puts "Detailed monitoring state: #{instance.monitoring.state}"
        puts "Public IP address:         #{instance.public_ip_address}"
        puts "Public DNS name:           #{instance.public_dns_name}"
        puts "VPC ID:                    #{instance.vpc_id}"
        puts "Subnet ID:                 #{instance.subnet_id}"
        if instance.tags.count.positive?
          puts 'Tags:'
          instance.tags.each do |tag|
            puts "                           #{tag.key}/#{tag.value}"
          end
        end
      end
    end
  end
end

# Full example call:
def run_me
  instance_id = ''
  region = ''
  # Print usage information and then stop.
  if ARGV[0] == '--help' || ARGV[0] == '-h'
    puts 'Usage:   ruby ec2-ruby-example-manage-instances.rb ' \
      'INSTANCE_ID REGION'
    puts 'Example: ruby ec2-ruby-example-manage-instances.rb ' \
      'i-033c48ef067af3dEX us-east-1'
    exit 1
  # If no values are specified at the command prompt, use these default values.
  elsif ARGV.count.zero?
    instance_id = 'i-033c48ef067af3dEX'
    region = 'us-east-1'
  # Otherwise, use the values as specified at the command prompt.
  else
    instance_id = ARGV[0]
    region = ARGV[1]
  end

  ec2_client = Aws::EC2::Client.new(region: region)

  puts 'Attempting to stop the instance. ' \
    'This might take a few minutes...'
  unless instance_stopped?(ec2_client, instance_id)
    puts 'Cannot stop the instance. Skipping this step.'
  end

  puts "\nAttempting to restart the instance. " \
    'This might take a few minutes...'
  unless instance_restarted?(ec2_client, instance_id)
    puts 'Cannot restart the instance. Skipping this step.'
  end

  puts "\nAttempting to reboot the instance. " \
    'This might take a few minutes...'
  unless instance_rebooted?(ec2_client, instance_id)
    puts 'Cannot reboot the instance. Skipping this step.'
  end

  puts "\nAttempting to enable detailed monitoring for the instance..."
  unless instance_detailed_monitoring_enabled?(ec2_client, instance_id)
    puts 'Cannot enable detailed monitoring for the instance. ' \
      'Skipping this step.'
  end

  puts "\nInformation about available instances:"
  list_instances_information(ec2_client)
end

run_me if $PROGRAM_NAME == __FILE__