---
layout: docs
page_title: Install - AWS ECS
description: >-
  Install Consul Service Mesh on AWS ECS (Elastic Container Service).
---

# Install

Installing Consul on ECS is a multi-part process:

1. [**Terraform:**](#terraform) Your tasks must be specified in Terraform using [`ecs_task_definition`](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/ecs_task_definition)
   and [`ecs_service`](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/ecs_service) resources.
1. [**Task Module:**](#task-module) You can then take your `ecs_task_definition` resources and copy their configuration into a new [`mesh-task` module](https://registry.terraform.io/modules/hashicorp/consul-ecs/aws/latest/submodules/mesh-task)
   resource that will add the necessary containers to the task definition.
1. [**Routing:**](#routing) With your tasks as part of the mesh, you must specify their upstream
   services and change the URLs the tasks are using so that they're making requests
   through the service mesh.
1. [**Bind Address:**](#bind-address) Now that all communication is flowing through the service mesh,
   you should change the address your application is listening on to `127.0.0.1`
   so that it only receives requests through the sidecar proxy.

-> **NOTE:** This page assumes you're familiar with ECS. See [What is Amazon Elastic Container Service](https://docs.aws.amazon.com/AmazonECS/latest/developerguide/Welcome.html) for more details.

## Terraform

Your tasks must first be specified in Terraform using [`ecs_task_definition`](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/ecs_task_definition)
and [`ecs_service`](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/ecs_service) resources so that
they can later be converted to use the [`mesh-task` module](https://registry.terraform.io/modules/hashicorp/consul-ecs/aws/latest/submodules/mesh-task).

For example, your tasks should be defined with Terraform similar to the following:

```hcl
resource "aws_ecs_task_definition" "my_task" {
  family                   = "my_task"
  requires_compatibilities = ["FARGATE"]
  network_mode             = "awsvpc"
  cpu                      = 256
  memory                   = 512
  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"
}
```

## Task Module

In order to add the necessary sidecar containers for your task to join the mesh,
you must use the [`mesh-task` module](https://registry.terraform.io/modules/hashicorp/consul-ecs/aws/latest/submodules/mesh-task).

The module will reference the same inputs as your old ECS task definition but it will
create a new version of the task definition with additional containers.

The `mesh-task` module is used as follows:

```hcl
module "my_task" {
  source  = "hashicorp/consul/aws-ecs//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"
  retry_join = "<address of the Consul server>"
}
```

All possible inputs are documented on the [module reference documentation](https://registry.terraform.io/modules/hashicorp/consul-ecs/aws/latest/submodules/mesh-task?tab=inputs)
however there are some important inputs worth highlighting:

- `family` is used as the [task definition family](https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task_definition_parameters.html#family)
  but it's also used as the name of the service that gets registered in Consul.
- `container_definitions` accepts an array of [container definitions](https://docs.aws.amazon.com/AmazonECS/latest/developerguide/task_definition_parameters.html#container_definitions).
  These are your application containers and this should be set to the same value as what you
  were passing into the `container_definitions` key in the `aws_ecs_task_definition` resource
  without the `jsonencode() function`.

  For example, if your original task definition looked like:

  ```hcl
  resource "aws_ecs_task_definition" "my_task" {
    ...
    container_definitions = jsonencode(
      [
        {
          name             = "example-client-app"
          image            = "docker.io/org/my_task:v0.0.1"
          essential        = true
          ...
        }
      ]
    )
  }
  ```

  Then you would remove the `jsonencode()` function and use the rest of the value
  as the input for the `mesh-task` module:

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

    ...
    container_definitions = [
      {
        name             = "example-client-app"
        image            = "docker.io/org/my_task:v0.0.1"
        essential        = true
        ...
      }
    ]
  }
  ```

- `port` is the port that your application listens on. This should be set to a
  string, not an integer, i.e. `port = "9090"`, not `port = 9090`.
- `consul_server_service_name` should be set to the name of the ECS service for
  the Consul dev server. This is an output of the `dev-server` module so it
  can be referenced, e.g. `consul_server_service_name = module.dev_consul_server.ecs_service_name`.

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

Your `aws_ecs_service` resource can remain unchanged except for the `task_definition`
input which should reference the new module's output of the task definition's ARN:

```hcl
resource "aws_ecs_service" "my_task" {
  ...
  task_definition = module.my_task.task_definition_arn
}
```

-> **NOTE:** If your tasks run in a public subnet, they must have `assign_public_ip = true`
in their [`network_configuration`](https://registry.terraform.io/providers/hashicorp/aws/latest/docs/resources/ecs_service#network_configuration) block so that ECS can pull the Docker images.

After running `terraform apply`, you should see your tasks registered in
the Consul UI.

## Routing

Now that your tasks are registered in the mesh, you're able to use the service
mesh to route between them.

In order to make calls through the service mesh, you must configure the sidecar
proxy to listen on a different port for each upstream service your application
needs to call. You then must modify your application to make requests to the sidecar
proxy on that port.

For example, say my application `web` wants to make calls to my other application
`backend`.

First, I must configure the `mesh-task` module's upstreams:

```hcl
module "web" {
  family = "web"
  upstreams = [
    {
      destination_name = "backend"
      local_bind_port  = 8080
    }
  ]
}
```

I set the `destination_name` to the name of the upstream service (in this case `backend`),
and I set `local_bind_port` to an unused port. This is the port that the sidecar proxy
will listen on and any requests to this port will be forwarded over to the `destination_name`.
This does not have to be the port that `backend` is listening on because the service mesh
will handle routing the request to the right port.

If you have multiple upstream services they'll each need to be listed here.

Next, I must configure my application to make requests to `localhost:8080` when
it wants to call the `backend` service.

For example, if my service allows configuring the URL for `backend` via the
`BACKEND_URL` environment variable, I would set:

```hcl
module "web" {
  family = "web"
  upstreams = [
    {
      destination_name = "backend"
      local_bind_port  = 8080
    }
  ]
  container_definitions = [
    {
      name        = "web"
      environment = [
        {
          name  = "BACKEND_URL"
          value = "http://localhost:8080"
        }
      ]
      ...
    }
  ]
  ...
}
```

## Bind Address

To ensure that your application only receives traffic through the service mesh,
you must change the address that your application is listening on to only the loopback address
(also known as `localhost`, `lo` and `127.0.0.1`)
so that only the sidecar proxy running in the same task can make requests to it.

If your application is listening on all interfaces, e.g. `0.0.0.0`, then other
applications can call it directly, bypassing its sidecar proxy.

Changing the listening address is specific to the language and framework you're
using in your application. Regardless of which language/framework you're using,
it's a good practice to make the address configurable via environment variable.

For example in Go, you would use:

```go
s := &http.Server{
	Addr:           "127.0.0.1:8080",
  ...
}
log.Fatal(s.ListenAndServe())
```

In Django you'd use:

```bash
python manage.py runserver "127.0.0.1:8080"
```

## Next Steps

- Now that your applications are running in the service mesh, read about
  other [Service Mesh features](/docs/connect).
- View the [Architecture](/docs/ecs/architecture) documentation to understand
  what's going on under the hood.
