AWS list of container_definitions using Terraform

Question

I'm trying to deploy an aws_ecs_task_definition with multiple container_defintions in Terraform. I have a variable like this, which I use also for other resources creation:

variable "entity_map" {
  type = map(object({
    name = string,
    port = number,
    image = string,
    type = string,
    ec2_enabled = bool
    ...
  }))
  default = {
    "entity1" = {
      name = "e1",
      port = 1651, 
      image = "link_to_image1"
      type = "B",
      ec2_enabled = true,
      ...
    },
    "entity2" = {
      name = "e2",
      port = 1655,
      image = "link_to_image2",
      type = "S", 
      ec2_enabled = true,
      ...
    },
    ...
  }
}

What I would like to do is iterate through each object (entity1, entity2, ...) and create as many container_definition inside the task definitions.

What I tried to do is to use dynamic block with the for_each approach but this gives me errors. For example

resource "aws_ecs_task_definition" "example" {
  family                   = "example-task"
  network_mode             = "awsvpc"
  requires_compatibilities = ["FARGATE"]

  execution_role_arn = aws_iam_role.ecs_execution_role.arn

  dynamic "container_definitions" {
    for_each = var.entity_map
    content {
      name  = each.value.name
      image = each.value.image
      portMappings {
        containerPort = each.value.port
        hostPort      = each.value.port
      }
    }
  }
...

The error is:

│ 210: dynamic "container_definitions" { │ │ Blocks of type "container_definitions" are not expected here.

Answer 1

There are a few issues here:

• container_definitions is a parameter, and not a block.
• The value of container_definitions should be a JSON format string.
• The variable type of var.entity_map is a map(object(...)), but the resource expects list(object(...)).
• The object type is not in the expected structure for the resource/API inputs.

Fixing all of these issues results in:

variable "entity_map" {
  type = list(object({
    name = string,
    portMappings = list(object{
      containerPort = number
      hostPort      = number
    })
    port = number,
    image = string
  }))
  default = [
    {
      name = "e1",
      portMappings = [{
        containerPort = 1651
        hostPort      = 1651
      }]
      image = "link_to_image1"
    },
    {
      name = "e2",
      portMappings = [{
        containerPort = 1655
        hostPort      = 1655
      }]
      image = "link_to_image2"
    },
    ...
  ]
}

resource "aws_ecs_task_definition" "example" {
  family                   = "example-task"
  network_mode             = "awsvpc"
  requires_compatibilities = ["FARGATE"]

  execution_role_arn = aws_iam_role.ecs_execution_role.arn

  container_definitions = jsonencode(var.entity_map)
  ...
}