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

# Installation

Installing Consul on ECS is a multi-part process:

1. [**Task Module:**](#task-module) Define the [`mesh-task` Terraform module](https://registry.terraform.io/modules/hashicorp/consul-ecs/aws/latest/submodules/mesh-task)
   to create a task definition with the necessary sidecar containers for your application to join the service mesh.
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.

## 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):

```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).
  This is where you include application containers.
- `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`.
- `retry_join` is passed to the `-retry-join` option for the Consul agent. This tells
  the agent the location of your Consul server so that it can join the Consul cluster.

To define an ECS service, reference the mesh-task module's `task_definition_arn` output value
in your `aws_ecs_service` resource:

```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 your application `web` wants to make calls to my other application
`backend`.

First, you must configure the `mesh-task` module's upstream(s):

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

- Set the `destination_name` to the name of the upstream service (in this case `backend`)
- Set `local_bind_port` to an unused port. This is the port that the sidecar proxy
  will listen on. 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 each need to be listed here.

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

For example, if your service allows configuring the URL for `backend` via the
`BACKEND_URL` environment variable, you 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

- Configure a secure [Production Installation](TODO-LINK).
- 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.