Dynamic Task Definition in Terraform - amazon-web-services

Question

At the moment I have multiple aws_ecs_task_definition that are blueprints for my ECS tasks. Rather than having a separate module to store each of these unique definitions, I would like to somehow structure my task definition to be agnostic so that it can be used for each of my containers. The main challenge I am facing is that the environment variables differ between task definitions. For example, one task definition might have 4 environment variables and another might have 12. Also, some of the values these variables have are provided by other modules by way of using Outputs (e.g. databases endpoints). Below is an example of an existing task definition.
resource "aws_ecs_task_definition" "service" {
execution_role_arn = var.ecsTaskExecutionRole
task_role_arn = var.ecsTaskExecutionRole
requires_compatibilities = ["FARGATE"]
family = "${var.name}-definition"
container_definitions = jsonencode([
{
"environment" : [
{ "name" : "database_endpoint",
"value" : "${var.database_endpoint}"
},
{ "name" : "database_password",
"value" : "admin"
}
],
"healthCheck" : {
"command" : [
"CMD-SHELL",
"echo \"hello\""
],
"interval" : 10,
"timeout" : 60,
"retries" : 10,
"startPeriod" : 60
},
command = ["start", "--auto-build"]
name = "${var.name}"
image = "${var.image}"
cpu = 1024
memory = 2048
essential = true
portMappings = [
{
containerPort = 7278
hostPort = 7278
}
]
},
])
network_mode = "awsvpc"
cpu = 1024
memory = 2048
runtime_platform {
operating_system_family = "LINUX"
}
}
In essence, I want to be able to dynamically build the environment list based on an object that is provided as a variable when making the module call. For example, that variable might look like this and the values that are empty string are updated at a later point:
containers = {
image1 = {
image = "imageUrl"
}
image2 = {
image = "imageUrl"
documentdb_endpoint = ""
}
image3 = {
image = "imageUrl"
redis_endpoint = ""
}
image4 = {
image = "imageUrl"
}
}
Would appreciate any advice to help make the code more concise.