Enable adding custom user data to ECS cluster

Currently, adding additional user data to an Autoscaling group and adding it to an ECS cluster is not a smooth experience.

The implementation of autoscalinggroup.addUserData() does not correctly process MIME multitype archives. E.g.:

    const asg = new autoscaling.AutoScalingGroup(this, 'MyFleet', {
      instanceType: new ec2.InstanceTypePair(ec2.InstanceClass.M4, ec2.InstanceSize.Large),
      machineImage: new ec2.AmazonLinuxImage(),
      associatePublicIpAddress: true,
      vpc
    });

    const userData = `
Content-Type: multipart/mixed; boundary="//"
MIME-Version: 1.0

--//
Content-Type: text/cloud-config; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment; filename="cloud-config.txt"

#cloud-config
cloud_final_modules:
- [scripts-user, always]

--//
Content-Type: text/x-shellscript; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment; filename="userdata.txt"

#!/bin/bash
/bin/echo "Hello World" >> /tmp/testfile.txt
--//
`
    asg.addUserData(userData);

    cluster.addAutoScalingGroupCapacity(asg);

Results in the following CFN for LaunchConfiguration:

  MyFleetLaunchConfig5D7F9801:
    Type: AWS::AutoScaling::LaunchConfiguration
    Properties:
      ImageId: ami-01e24be29428c15b2
      InstanceType: m4.large
      AssociatePublicIpAddress: true
      IamInstanceProfile:
        Ref: MyFleetInstanceProfile70A58496
      KeyName: hhh-2
      SecurityGroups:
        - Fn::GetAtt:
            - MyFleetInstanceSecurityGroup774E8234
            - GroupId
      UserData:
        Fn::Base64:
          Fn::Join:
            - ""
            - - |-
                #!/bin/bash

                Content-Type: multipart/mixed; boundary="//"
                MIME-Version: 1.0

                --//
                Content-Type: text/cloud-config; charset="us-ascii"
                MIME-Version: 1.0
                Content-Transfer-Encoding: 7bit
                Content-Disposition: attachment; filename="cloud-config.txt"

                #cloud-config
                cloud_final_modules:
                - [scripts-user, always]

                --//
                Content-Type: text/x-shellscript; charset="us-ascii"
                MIME-Version: 1.0
                Content-Transfer-Encoding: 7bit
                Content-Disposition: attachment; filename="userdata.txt"

                #!/bin/bash
                /bin/echo "Hello World" >> /tmp/testfile.txt
                --//

                echo ECS_CLUSTER=
              - Ref: Ec2ClusterEE43E89D
              - >-2
                 >> /etc/ecs/ecs.config
                sudo iptables --insert FORWARD 1 --in-interface docker+ --destination 169.254.169.254/32 --jump DROP

                sudo service iptables save

                echo ECS_AWSVPC_BLOCK_IMDS=true >> /etc/ecs/ecs.config

When deployed, the User Data on the ec2 instance looks like this:

#!/bin/bash

Content-Type: multipart/mixed; boundary="//"
MIME-Version: 1.0

--//
Content-Type: text/cloud-config; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment; filename="cloud-config.txt"

#cloud-config
cloud_final_modules:
- [scripts-user, always]

--//
Content-Type: text/x-shellscript; charset="us-ascii"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Disposition: attachment; filename="userdata.txt"

#!/bin/bash
/bin/echo "Hello World" >> /tmp/testfile.txt
--//

echo ECS_CLUSTER=CustomUserData-Ec2ClusterEE43E89D-1H8KFTDM00P66 >> /etc/ecs/ecs.config
sudo iptables --insert FORWARD 1 --in-interface docker+ --destination 169.254.169.254/32 --jump DROP
sudo service iptables save
echo ECS_AWSVPC_BLOCK_IMDS=true >> /etc/ecs/ecs.config

It should look like this:

Content-Type: multipart/mixed; boundary="36b51cd254c2a10606cc4ea1d7c161a960c25b43fbcf3f2275bfea986b64"
MIME-Version: 1.0

--36b51cd254c2a10606cc4ea1d7c161a960c25b43fbcf3f2275bfea986b64
Content-Disposition: attachment; filename="cloud-config.txt"
Content-Transfer-Encoding: 7bit
Content-Type: text/cloud-config; charset="us-ascii"
Mime-Version: 1.0

#cloud-config
cloud_final_modules:
- [scripts-user, always]

--36b51cd254c2a10606cc4ea1d7c161a960c25b43fbcf3f2275bfea986b64
Content-Disposition: attachment; filename="userdata.txt"
Content-Transfer-Encoding: 7bit
Content-Type: text/x-shellscript; charset="us-ascii"
Mime-Version: 1.0

#!/bin/bash
/bin/echo "Hello World" >> /tmp/testfile.txt
--36b51cd254c2a10606cc4ea1d7c161a960c25b43fbcf3f2275bfea986b64
Content-Type: text/text/x-shellscript; charset="utf-8"
Mime-Version: 1.0


#!/bin/bash
echo ECS_CLUSTER=blargh >> /etc/ecs/ecs.config

--36b51cd254c2a10606cc4ea1d7c161a960c25b43fbcf3f2275bfea986b64--

The above was generated using the ECS-cli with custom user data flag: ecs-cli up --extra-user-data custom-user-data.txt --cluster blargh --capability-iam Though the ECS CLI is able to leverage some go libraries for MIME multipart archive constructing/unpacking.

It would nice to have a smoother API around adding custom user data – not sure if that’s better served through an integration with a higher-level ECS construct or modifying the existing API in the Autoscaling library.

[rsmogura]

@kristianmandrup, This property is a getter (it’s a function), it can give undefined value if the capacity has not been defined in props, during creation of cluster (that’s one way of defining capacity).

If you use method addCapacity to add a capacity (instead of props), then the result value is an autoscaling group (cluster can be associated with multiple ASG) and you can use it to operate on user data.

As a side note, there’s new set of changes enabling capacity providers, AFIK.

[rix0rrr]

Custom user data generously supplied by @hoegertn should give you a way to achieve what you need:

https://github.com/aws/aws-cdk/pull/4193

@marcb still interested to hear in what you need to achieve that cfn-init can not cover in the same way that userdata would?