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Update AMIs within AWS Auto Scaling groups automatically.

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AWS Auto Scaling Groups Updater

AWS Auto Scaling group is a great way of managing Amazon EC2 instances. AWS Auto Scaling group watches the corresponding instances' health and launches new instances whenever needed: to replace instances that became unhealthy or to scale the group. Furthermore, with an AWS Elastic Load Balancer attached, AWS Auto Scaling Group also takes ELB health checks into account, making it possible to replace the instances based on service-level signals.

However, when it comes to updating services, AWS Auto Scaling Groups become tricky. The recommended way is to create the group using a launch template containing the information required to launch new instances, such as instance type and Amazon Machine Image (AMI). Hence, to update the service, one needs to create a new AMI, update the corresponding launch template, and execute an instance refresh.

This is where AWS Auto Scaling Groups Updater comes in handy. It uses AWS EC2 API and AWS EC2 Auto Scaling API to perform the following operations automatically:

  • register a new AMI from a running instance;
  • create a new version of the Auto Scaling group's launch template with this new AMI attached;
  • execute the instance refresh for the Auto Scaling group;
  • cancel the instance refresh if it's unable to finish within the desired time;
  • handle all the errors that might happen along the way.

The tool uses the default AWS credentials config. Run aws configure or set up the environment variables AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, and AWS_REGION before running the tool.

Examples of Use

The program options to create a new AMI from the instance i-0d8767eed40de1728, name it service_ami, update the Auto Scaling group my_service_group with it:

aws_asg_updater --group my_service_group --instance i-0d8767eed40de1728 --ami service_ami

The output looks like that then:

2022/01/02 00:23:02 creating image "service_ami" from the instance i-0d8767eed40de1728
2022/01/02 00:24:03 creating image service_ami (ami-070a1f039b2945569): pending
2022/01/02 00:25:04 creating image service_ami (ami-070a1f039b2945569): pending
2022/01/02 00:26:04 creating image service_ami (ami-070a1f039b2945569): available
2022/01/02 00:26:04 created image "ami-070a1f039b2945569" from instance i-0d8767eed40de1728
2022/01/02 00:26:05 launch template id: lt-0b049e246796cc5cd
2022/01/02 00:26:05 latest launch template version id: 19
2022/01/02 00:26:06 created new version 20 for the launch template lt-0b049e246796cc5cd
2022/01/02 00:26:06 set the version 20 for the launch template lt-0b049e246796cc5cd as default
2022/01/02 00:26:06 will run instance refresh for the auto scale group "my_service_group"
2022/01/02 00:27:07 updating group my_service_group, update id 1608d67f-931c-4e83-8aff-56721c95e86a: InProgress, 0% completion
2022/01/02 00:28:08 updating group my_service_group, update id 1608d67f-931c-4e83-8aff-56721c95e86a: InProgress, 0% completion
2022/01/02 00:29:09 updating group my_service_group, update id 1608d67f-931c-4e83-8aff-56721c95e86a: InProgress, 0% completion
2022/01/02 00:30:10 updating group my_service_group, update id 1608d67f-931c-4e83-8aff-56721c95e86a: InProgress, 0% completion
2022/01/02 00:31:11 updating group my_service_group, update id 1608d67f-931c-4e83-8aff-56721c95e86a: Successful, 100% completion
2022/01/02 00:31:11 instance refresh for the auto scale group "my_service_group" completed successfully

If you already have an AMI ID, just skip the --ami and --instance options, and use the --image option, e.g.:

aws_asg_updater --group my_service_group --image ami-070a1f039b2945569

This will update the launch template and run the instance refresh:

2022/01/02 11:36:09 launch template id: lt-0b049e246796cc5cd
2022/01/02 11:36:10 latest launch template version id: 20
2022/01/02 11:36:10 created new version 21 for the launch template lt-0b049e246796cc5cd
2022/01/02 11:36:11 set the version 21 for the launch template lt-0b049e246796cc5cd as default
2022/01/02 11:36:11 will run instance refresh for the auto scale group "appscience_bot"
2022/01/02 11:37:12 updating group appscience_bot, update id 197f64f8-9b1e-4a9c-b4ad-85b7882ca170: InProgress, 0% completion
2022/01/02 11:38:13 updating group appscience_bot, update id 197f64f8-9b1e-4a9c-b4ad-85b7882ca170: InProgress, 0% completion
2022/01/02 11:39:14 updating group appscience_bot, update id 197f64f8-9b1e-4a9c-b4ad-85b7882ca170: InProgress, 0% completion
2022/01/02 11:40:15 updating group appscience_bot, update id 197f64f8-9b1e-4a9c-b4ad-85b7882ca170: InProgress, 0% completion
2022/01/02 11:41:15 updating group appscience_bot, update id 197f64f8-9b1e-4a9c-b4ad-85b7882ca170: InProgress, 0% completion
2022/01/02 11:42:16 updating group appscience_bot, update id 197f64f8-9b1e-4a9c-b4ad-85b7882ca170: Successful, 100% completion
2022/01/02 11:42:16 instance refresh for the auto scale group "appscience_bot" completed successfully

Program Arguments

  • group: the name of the Auto Scaling group to update; required.
  • image: AMI id to update the group; optional: do not use if you want to create an AMI from a running instance.
  • instance: AWS EC2 instance ID to create the AMI from; optional: do not use if you already have an AMI ID.
  • ami: the name of the AMI to be created from the selected instance; optional: use together with the --instance argument only.
  • update-timeout: the time limit to complete the instance refresh; optional: the default is 30 minutes. Use the Golang duration strings to override, see https://pkg.go.dev/time#ParseDuration.
  • update-tick: the time between status updates in the log file; optional: the default is one minute. Making this parameter lower might speed up the overall execution. Use the Golang duration strings to override, see https://pkg.go.dev/time#ParseDuration.

Installation

Assuming you already have Golang installed on the machine, simply run:

go install github.com/ashagraev/aws_asg_updater@latest

The tool will then appear in your golang binary folder (e.g., ~/go/bin/aws_asg_updater). If you don't have Golang yet, consider installing it using the official guide https://go.dev/doc/install.

Alternatively, you can download the pre-built binaries from the latest release: https://github.com/ashagraev/aws_asg_updater/releases/latest.

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