consul/website/content/docs/ecs/deploy/migrate-existing-tasks.mdx

---
layout: docs
page_title: Migrate existing tasks to Consul service mesh
description: >-
  You can migrate tasks in existing Amazon Web Services ECS deployments to a service mesh deployed with Terraform. Learn how to convert a task specified as an ECS task definition into a `mesh-task` Terraform module.
---

# Migrate existing tasks to Consul on ECS with Terraform 

To migrate existing tasks to Consul, rewrite the existing Terraform code for your tasks so that the container definitions include the [`mesh-task` Terraform module](https://registry.terraform.io/modules/hashicorp/consul-ecs/aws/latest/submodules/mesh-task). 

Your tasks must already be defined in Terraform using the `ecs_task_definition` resource so that they can then be converted to use the `mesh-task` module.

## Example 

The following example shows an existing task definition configured in Terraform:

```hcl
resource "aws_ecs_task_definition" "my_task" {
  family                   = "my_task"
  requires_compatibilities = ["FARGATE"]
  network_mode             = "awsvpc"
  cpu                      = 256
  memory                   = 512
  execution_role_arn       = "arn:aws:iam::111111111111:role/execution-role"
  task_role_arn            = "arn:aws:iam::111111111111:role/task-role"
  container_definitions = jsonencode(
    [{
      name             = "example-client-app"
      image            = "docker.io/org/my_task:v0.0.1"
      essential        = true
      portMappings = [
        {
          containerPort = 9090
          hostPort      = 9090
          protocol      = "tcp"
        }
      ]
      cpu         = 0
      mountPoints = []
      volumesFrom = []
    }]
  )
}

resource "aws_ecs_service" "my_task" {
  name            = "my_task"
  cluster         = "arn:aws:ecs:us-east-1:111111111111:cluster/my-cluster"
  task_definition = aws_ecs_task_definition.my_task.arn
  desired_count   = 1
  network_configuration {
    subnets = ["subnet-abc123"]
  }
  launch_type            = "FARGATE"
}
```


Replace the `aws_ecs_task_definition` resource with the `mesh-task` module so that Consul adds the necessary dataplane containers that enable your task to join the mesh. The `mesh-task` module uses inputs similar to your old ECS task definition but creates a new version of the task definition with additional containers.

The following Terraform configuration uses the `mesh-task` module to replace the previous example's task definition:

```hcl
module "my_task" {
  source  = "hashicorp/consul-ecs/aws//modules/mesh-task"
  version = "<latest version>"

  family                = "my_task"
  container_definitions = [
    {
      name         = "example-client-app"
      image        = "docker.io/org/my_task:v0.0.1"
      essential    = true
      portMappings = [
        {
          containerPort = 9090
          hostPort      = 9090
          protocol      = "tcp"
        }
      ]
      cpu         = 0
      mountPoints = []
      volumesFrom = []
    }
  ]

  port       = 9090
  consul_server_hosts = "<address of the Consul server>"
}

```

Note the following differences:

- The `execution_role_arn` and `task_role_arn` fields are removed. The `mesh-task` module creates the task and execution roles by default. If you need to use existing IAM roles, set the `task_role` and `execution_role` fields to pass in existing roles.
- The `port` field specifes the port that your application listens on. If your application has no listening port, set `outbound_only = true` and remove the `port` field.
- The `jsonencode()` function is removed from the `container_definitions` field.

The `mesh-task` module creates a new version of your task definition with the necessary dataplane containers so you can delete your existing `aws_ecs_task_definition` resource.