AWS ECS ssh helper

ecs-ssh.rb

#!/usr/bin/ruby
require 'json'
$sshUser = 'ec2user'
#NOTE all of our ecs clusters are prefixed with "ecs-" 
#which we assume here to save the time & trouble of having to type that out
#all of our tasks are also suffixed with the "environment" name
def sshToEcsInstance(clusterName)
    cmd = "aws ecs list-container-instances --cluster ecs-"+ clusterName
    instances =  JSON.parse(`#{cmd}`)["containerInstanceArns"]
    ec2InstanceHostname = getInstanceInfo(clusterName, instances.sample)
    system("ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -J bastion #{$sshUser}@#{ec2InstanceHostname}")
end

def sshToTask(clusterName, taskName, subcommand)
    cmd = "aws ecs list-tasks --cluster ecs-"+ clusterName
    taskArns = JSON.parse(`#{cmd}`)["taskArns"].join(' ')
    tasks = JSON.parse(` aws ecs describe-tasks --cluster ecs-#{clusterName} --tasks #{taskArns}`)['tasks']
    tasks = tasks.select {|task|task["group"] == "service:#{taskName}-#{clusterName}"}
    containerArns = tasks.map{ |x| x["containerInstanceArn"]}.flatten
    ec2InstanceHostname = getInstanceInfo(clusterName, containerArns.sample)

    system("ssh -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null -J bastion -t #{$sshUser}@#{ec2InstanceHostname} run-task #{taskName} #{subcommand}") 
end

def getInstanceInfo(clusterName, containerArn)
    ecsInstanceInfo = JSON.parse(`aws ecs describe-container-instances --cluster ecs-#{clusterName} --container-instances #{containerArn}`)["containerInstances"][0];
    instanceId = ecsInstanceInfo["ec2InstanceId"];
    ec2InstanceInfo = JSON.parse(`aws ec2 describe-instances --instance-ids #{instanceId}`)["Reservations"][0]["Instances"][0];
    ec2InstanceIp = ec2InstanceInfo["PrivateIpAddress"];
    #print ec2InstanceInfo["NetworkInterfaces"][0]
    #PrivateIpAddress
    #PrivateDnsName
    ec2InstanceHostname = ec2InstanceInfo["NetworkInterfaces"][0]["PrivateIpAddress"];
end


clusterName = ARGV.shift
taskName    = ARGV.shift
args        = ARGV.join(' ')
subcommand  = (args.empty?) ? 'bash' : args
#print taskName.inspect
#print clusterName.inspect
#print subcommand.inspect

if taskName.nil?
    print "Finding instance in cluster: #{clusterName}"
    sshToEcsInstance(clusterName)
else 
    print "Finding container running task: #{taskName}"
    sshToTask(clusterName, taskName, subcommand)
end