Creating a SSM Composite Document that pulls Parameters from Parameter Store - AWS - amazon-web-services

Question

The task is simple: whenever an EC2 instance is launched with tag key:value I want it to install a specific software. Whenever an EC2 instance is launched with a different tag key:value I want it to install a different software.
I understand that I can create 2 different associations in State Manager that uses runCommand RuneRemoteScript to install software based on the tags, but the goal is to have 1 composite document that can do this.
Any help / guidance would be appreciated!

Answer 1

You can achieve that using SSM Automation documents - https://docs.aws.amazon.com/systems-manager/latest/userguide/automation-branchdocs.html
However, probably you will need to do something like this:
In the State Manager use AWS-RunDocument,
This document should execute SSM Automation document (your Composite document)
Your Composite document should look like this:
I didn't validate this template, and I assume It shouldn't work without a few days of debugging
schemaVersion: '0.3'
parameters:
InstanceId:
type: String
mainSteps:
- name: DescribeEc2
action: 'aws:executeScript'
inputs:
Runtime: python3.7
Handler: script_handler
Script: |
import json
import boto3
def script_handler(events):
ec2_instance = boto3.client('ec2').describe_instances(
InstanceIds=events["instance_id"],
)["Reservations"][0]["Instances"][0]
# thread it like an example,
# Here you should parse your tags and decide what software you
# want to install on the provided instance
return json.dumps(
{
"to_be_installed": "result"
},
sort_keys=True,
default=str
)
InputPayload:
instance_id: '{{ InstanceId }}'
Outputs:
- Name: result
Selector: "$.to_be_installed"
- name: WhatToInstall
action: aws:branch
inputs:
Choices:
- NextStep: InstallSoft1
Variable: "{{DescribeEc2.result}}"
StringEquals: soft_1
- NextStep: InstallSoft1
Variable: "{{DescribeEc2.result}}"
StringEquals: soft_2
- name: InstallSoft1
action: aws:runCommand
inputs:
DocumentName: AWS-RunShellScript
InstanceIds:
- '{{ InstanceId }}'
Parameters:
commands:
...
- name: InstallSoft2
action: aws:runCommand
inputs:
DocumentName: AWS-RunShellScript
InstanceIds:
- '{{ InstanceId }}'
Parameters:
commands:
...
Tbh, you will find a lot of troubles with such solution (IAM and SSM specific issues), so I will recommend using Event Bridge -> Lambda Function(that decides which Document/Automation should be run) -> SSM-RunDocument (executed directly in the Lambda Function).