How to use StringMap parameters in SSM documents? - amazon-web-services

Question

I have the following step in a SSM document. The result of the call is a Json, so I wanted to parse it as a stringMap (which seems to be the correct type for it) instead of creating an output for each variable I want to reference
I've tried referencing this as both:
{{ GetLoadBalancerProperties.Description.Scheme }}
and
{{ GetLoadBalancerProperties.Description[\"LoadBalancerName\"] }}
In both cases I get an error saying the variable was never defined
{
"name": "GetLoadBalancerProperties",
"action": "aws:executeAwsApi",
"isCritical": true,
"maxAttempts": 1,
"onFailure": "step:deleteParseCloudFormationTemplate",
"inputs": {
"Service": "elb",
"Api": "describe-load-balancers",
"LoadBalancerNames": [
"{{ ResourceId }}"
]
},
"outputs": [
{
"Name": "Description",
"Selector": "$.LoadBalancerDescriptions[0]",
"Type": "StringMap"
}
]
}
This is the actual message:
Step fails when it is validating and resolving the step inputs. Failed to resolve input: GetLoadBalancerProperties.Description["LoadBalancerName"] to type String. GetLoadBalancerProperties.Description["LoadBalancerName"] is not defined in the Automation Document.. Please refer to Automation Service Troubleshooting Guide for more diagnosis details.

Answer 1

I believe the answer you were searching is in here:
https://docs.aws.amazon.com/systems-manager/latest/userguide/ssm-plugins.html#top-level-properties-type
Just to name a few examples:
Map type is a Python dict, hence if your output is a dict you should use StringMap in the SSM Document.
While List type is same as Python list.
So if your output is a List of Dictionary the type you want to use is MapList.

Answer 2

In some cases it seems that you cannot. I was able to work around this issue, by using a Python script in the SSM document to output the right type, but otherwise I believe the SSM document is not flexible enough to cover all cases.
The script I used:
- name: myMainStep
action: aws:executeScript
inputs:
Runtime: python3.6
Handler: myMainStep
InputPayload:
param: "{{ myPreviousStep.myOutput }}"
Script: |-
def myMainStep(events,context):
myOutput = events['myOutput']
for tag in myOutput:
if tag["Key"] == "myKey":
return tag["Value"]
return "myDefaultValue"
outputs:
- Name: output
Selector: "$.Payload"
Type: String
You can find out what the myOutput should be in AWS web console > SSM > Automation > Your execution, if you have already executed your automation once > executeScript step > input parameters