ecs_cluster_exec.rb

#!/usr/bin/env ruby
# Executes a given command on a given ecs cluster
# Usage:
#   ./ecs_cluster_exec.rb cluster-name docker ps

def command_pipe(*commands)
  commands.join(' | ')
end

def get_cluster_host_arns(cluster_name)
  command_pipe(
    "aws ecs list-container-instances --cluster #{cluster_name} --output text",
    "awk '{split($2,a,\"/\"); print a[2]}'"
  )
end

def get_cluster_host_ids(cluster_name)
  command_pipe(
    "aws ecs describe-container-instances --output text --cluster #{cluster_name} --container-instances $(#{get_cluster_host_arns(cluster_name)})",
    "grep CONTAINERINSTANCES",
    "awk '{print $4}'"
  )
end

def get_instance_address(id)
  command_pipe(
    "aws ec2 describe-instances --instance-ids=#{id}",
    "grep ASSOCIATION",
    "head -n1",
    "awk '{print $3}'"
  )
end

def ec2_run_command(server_address, command)
  "ssh ec2-user@#{server_address} \"#{command}\""
end

def run(cmd)
  `#{cmd}`.split("\n")
end

cluster_name = ARGV[0] || (raise "Missing first argument cluster_name")
raise "Missing command to execute on cluster" if ARGV.length < 2
command = ARGV[1..-1].join(' ')

cluster_host_ids = run(get_cluster_host_ids(cluster_name))
puts cluster_host_ids.map { |id|
  run(get_instance_address(id))[0]
}.map { |ec2_address|
  run(ec2_run_command(ec2_address, command)).map { |ps_row|
    "#{ec2_address}\t#{ps_row}"
  }
}