ECS Service can't attach target group from different region

Question

I have an ECS Service to which I want to attach two load balancers, and one of those load balancers is in a different region of the ECS Cluster. When I try to apply changes I get the following error.

 InvalidParameterException: Unable to assume role and validate the specified targetGroupArn. Please verify that the ECS service role being passed has the proper permissions.

Here is terraform code I'm using and the output of the terraform plan:

resource "aws_ecs_service" "monitoring_grafana_service" {
  name            = "grafana"
  cluster         = module.ecs.ecs_cluster_arn  
  task_definition = aws_ecs_task_definition.monitoring_grafana_task.arn
  desired_count   = 1

  network_configuration{
    subnets = module.monitoring_vpc.private_subnets  
    security_groups = [ module.grafana_sg.security_group_id ]
  }

  load_balancer {
    target_group_arn = module.frontend_alb.target_group_arns[0]
    container_name   = "grafana"
    container_port   = 3000
  }


  load_balancer {
    target_group_arn = data.terraform_remote_state.ireland_vpc.outputs.oss_target_group_arns[0]
    container_name   = "grafana"
    container_port   = 3000
  }
  
  lifecycle {
    ignore_changes = [
      capacity_provider_strategy
    ]
  }
}

Output:

      + load_balancer {
      + container_name   = "grafana"
      + container_port   = 3000
      + target_group_arn = "arn:aws:elasticloadbalancing:eu-central-1:myAcc:targetgroup/grafna20220202125410761200000016/1cdafdd8e73c1d9a"
    }
  + load_balancer {
      + container_name   = "grafana"
      + container_port   = 3000
      + target_group_arn = "arn:aws:elasticloadbalancing:eu-west-1:myAcc:targetgroup/grafna20220203130531009700000004/ff91959dcf50287e"
    }

The Service Role used by ECS is the "default" one, created by AWS. It has the AWS managed policy: AmazonECSServiceRolePolicy

Answer 1

Clusters are Region-specific. that could be the reason.

Network Load Balancers now support connections from clients to IP-based targets in peered VPCs across different AWS Regions.

Make sure your VPC has peered connection to target resource

https://docs.aws.amazon.com/AmazonECS/latest/developerguide/service-load-balancing.html