[SOLVED] How to pass Pulumi's Output<T> to the container definition of a task within ecs?

Issue

A containerDefinition within a Task Definition needs to be provided as a single valid JSON document. I’m creating a generic ECS service that should handle dynamic data. Here is the code:

genericClientService(environment: string, targetGroupArn: Output<string>) {
return new aws.ecs.Service(`${this.domainName}-client-service-${environment}`, {
  cluster: this.clientCluster.id,
  taskDefinition: new aws.ecs.TaskDefinition(`${this.domainName}-client-${environment}`, {
    family: `${this.domainName}-client-${environment}`,
    containerDefinitions: JSON.stringify(
      clientTemplate(
        this.defaultRegion,
        this.domainName,
        this.taskEnvVars?.filter((object: { ENVIRONMENT: string }) => object.ENVIRONMENT === environment),
        this.ecrRepositories
      )
    ),
    cpu: "256",
    executionRoleArn: taskDefinitionRole.arn,
    memory: "512",
    networkMode: "awsvpc",
    requiresCompatibilities: ["FARGATE"],
  }).arn,
  desiredCount: 1,
  ...

There is a need of information from an already built resource this.ecrRepositories which represents a list of ECR repositories needed. The problem here is that let’s say you want to retrieve the repository URL and apply the necessary ‘apply()’ method, it will return an Output<string>. This would be fine normally, but since containerDefinitions needs to be a valid JSON document, Pulumi can’t handle it since JSON on an Output<T> is not supported;

Calling [toJSON] on an [Output<T>] is not supported. To get the value of an Output as a JSON value or JSON string consider either: 1: o.apply(v => v.toJSON()) 2: o.apply(v => JSON.stringify(v)) See https://pulumi.io/help/outputs for more details. This function may throw in a future version of @pulumi/pulumi.
Blockquote

Neither of the suggested considerations above will work as the dynamicly passed variables are wrapped within a toJSON function callback. Because of this it won’t matter how you pass resource information since it will always be an Output<T>.

Is there a way how to deal with this issue?

Solution

Assuming clientTemplate works correctly and the error happens in the snippet that you shared, you should be able to solve it with

containerDefinitions: pulumi.all(
    clientTemplate(
        this.defaultRegion,
        this.domainName,
        this.taskEnvVars?.filter((object: { ENVIRONMENT: string }) => object.ENVIRONMENT === environment),
        this.ecrRepositories
  )).apply(JSON.stringify),

Answered By – Mikhail Shilkov

Answer Checked By – Senaida (BugsFixing Volunteer)