How do I modify parameters in a Container Overrides section of a Step Functions machine? - json

Question

I have a Step Functions Machine the definition file of which looks as such:
"ContainerOverrides": [
{
"Name": "Foo",
"Environment": [
{
"Name": "Foo"
"Value": "Bar"
},
],
"Command.$": "States.Array($.Foo,$.Foo,$.Bar,$.Bar,$.Bar)"
}
]
},
that I am trying to rewrite into Typescript (CDK). I've gotten the following few lines.
containerOverrides: [{
containerDefinition: Foo,
environment: [
{ name: 'Foo', value: 'Bar'},
],
command: ['States.Array($.Foo,$.Foo,$.Bar,$.Bar,$.Bar)'],
}],
I'm a bit confused about how to go about this.
When I deploy the above CDK code, I get as output:
"Command": [
"States.Array($.Foo,$.Foo,$.Bar,$.Bar,$.Bar)"
],
My confusion is in regards to the following: The ContainerOverrides method doesn't accept parameters, but I need to modify a parameter (Command.$), so how can I possibly do that? I came across this post where somebody seems to have a similar issue, but when I try to apply the proposed solution, of simply writing
command: JsonPath.arrayAt('States.Array($.Foo,$.Foo,$.Bar,$.Bar,$.Bar)'
I get told that ''Cannot use JsonPath fields in an array, they must be used in objects''

Answer 1

TL;DR The current implementation of EcsRunTask doesn't permit this. The general-purpose CallAwsService construct does.
The EcsRunTask construct is the CDK's implementation of the ECS optimised integration. The construct only accepts an array of strings as override commands. It cannot produce substitutable output like "Command.$": "$.commands" that's needed to read the override command from the execution input. This is a limitation of the CDK implementation, not of the ECS optimized integration itself.
The cleanest solution is to use the CallAwsService construct, which implements the SDK service integration. It requires manual configuration. The API-specific config goes in the parameters prop. The prop is loosely typed as { [string]: any }. It's flexible, but it's your job to provide the expected syntax for the ecs:RunTask SDK call. Here is the relevant bit for your question:
parameters {
Overrides: {
ContainerOverrides: [
{ Command: sfn.JsonPath.array("sh", "-c", sfn.JsonPath.stringAt("$.cmd")), },
],
},
}
It produces the expected command override in the Step Functions task definition:
"Command.$": "States.Array('sh', '-c', $.cmd)"