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Add support for FARGATE #3

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7 changes: 7 additions & 0 deletions README.md
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Expand Up @@ -76,6 +76,13 @@ The workflow for each part is basically quite the same:
3. Run `terraform plan -var-file=configuration.tfvars` and confirm changes
4. Run `terraform apply -var-file=configuration.tfvars`

## Fargate

By default the ECS cluster is deployed on EC2 ECS instances. Specifying variable
```
launch_type = "FARGATE"
```
will cause the cluster to use FARGATE infrastructure. Currently fargate doesn't support docker private registries. Only Amazon's ECR Registry and Docker Public Registries.

## Additional information

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2 changes: 2 additions & 0 deletions asg/alb.tf
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Expand Up @@ -17,6 +17,8 @@ resource "aws_alb_target_group" "webapp_tg" {

deregistration_delay = 180

target_type = "${var.launch_type == "FARGATE" ? "ip" : "instance"}"

health_check {
interval = "60"
path = "/"
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5 changes: 4 additions & 1 deletion asg/autoscaling.tf
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@@ -1,4 +1,5 @@
resource "aws_launch_configuration" "webapp_on_demand" {
count = "${var.launch_type == "FARGATE" ? 0 : 1}"
instance_type = "${var.instance_type}"
image_id = "${lookup(var.ecs_image_id, var.aws_region)}"
iam_instance_profile = "${var.ecs_instance_profile}"
Expand All @@ -13,10 +14,11 @@ resource "aws_launch_configuration" "webapp_on_demand" {
}

resource "aws_autoscaling_group" "webapp_on_demand" {
count = "${var.launch_type == "FARGATE" ? 0 : 1}"
name = "${var.name_prefix}_webapp_on_demand"
max_size = 50
min_size = 0
desired_capacity = "${var.desired_capacity_on_demand}"
desired_capacity = "${var.desired_capacity_on_demand}"
health_check_grace_period = 300
health_check_type = "EC2"
force_delete = true
Expand All @@ -35,6 +37,7 @@ resource "aws_autoscaling_group" "webapp_on_demand" {
}

data "template_file" "autoscaling_user_data" {
count = "${var.launch_type == "FARGATE" ? 0 : 1}"
template = "${file("autoscaling_user_data.tpl")}"
vars {
ecs_cluster = "${aws_ecs_cluster.webapp_cluster.name}"
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5 changes: 3 additions & 2 deletions asg/configuration.tfvars
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Expand Up @@ -10,7 +10,7 @@ desired_capacity_on_demand = 2
ec2_key_name = "key-name"
instance_type = "t2.micro"
minimum_healthy_percent_webapp = 50

launch_type = "EC2" # can also be "FARGATE"
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desired_capacity_on_demand, ec2_key_name, and instance_type are also not needed for Fargate.

And also, I guess it makes more sense to use us-east-1 in the aws_region example here (instead of ap-northeast-1).

##
# This is a sample (public) Docker image from which can be accessed at https://github.com/docker-training/webapp
# This sample image utilizes Flask and it's not RECOMMENDED to run it directly in production (performance degradation)
Expand All @@ -20,7 +20,7 @@ webapp_docker_image_name = "training/webapp"
webapp_docker_image_tag = "latest"

##
# These variables are required, please fill it out with your environment outputs
# These variables are required, please fill it out with your environment outputs or use remote state references
##
sg_webapp_albs_id = "sg-12345678"
sg_webapp_instances_id = "sg-23456789"
Expand All @@ -29,3 +29,4 @@ subnet_ids = "subnet-34567890,subnet-4567890a"

ecs_instance_profile = "arn:aws:iam::123456789012:instance-profile/tutorial-test_ecs_instance_profile"
ecs_service_role = "tutorial-test_ecs_service_role"
ecs_task_execution_role = "arn:aws:iam::123456789012:role/tutorial-test_ecs_task_execution_role" # only used with launch type FARGATE
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ecs_service_role is not needed for FARGATE.

43 changes: 43 additions & 0 deletions asg/ecs.tf
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Expand Up @@ -5,6 +5,7 @@ resource "aws_ecs_cluster" "webapp_cluster" {

/* ECS service definition */
resource "aws_ecs_service" "webapp_service" {
count = "${var.launch_type == "FARGATE" ? 0 : 1}"
name = "${var.name_prefix}_webapp_service"
cluster = "${aws_ecs_cluster.webapp_cluster.id}"
task_definition = "${aws_ecs_task_definition.webapp_definition.arn}"
Expand All @@ -23,9 +24,51 @@ resource "aws_ecs_service" "webapp_service" {
}
}

resource "aws_ecs_service" "webapp_service_fargate" {
count = "${var.launch_type == "FARGATE" ? 1 : 0}"
name = "${var.name_prefix}_webapp_service"
cluster = "${aws_ecs_cluster.webapp_cluster.id}"
task_definition = "${aws_ecs_task_definition.webapp_definition_fargate.arn}"
launch_type = "FARGATE"
desired_count = "${var.count_webapp}"
deployment_minimum_healthy_percent = "${var.minimum_healthy_percent_webapp}"
iam_role = "${var.ecs_service_role}"
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@freedomofkeima freedomofkeima May 28, 2018 •
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With Fargate, we don't need to create ecs_service_role or even pass iam_role here, since Fargate will automatically use service-linked roles for ECS.

You cannot specify an IAM role for services that require a service linked role

See: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/using-service-linked-roles.html

It might be good to put this URL in the README.md, in case someone needs to use custom rule service linked roles.

For now, I think it's a good idea to put launch_type variable in static and we can decide whether we need to create ecs_service_role via count = "${var.launch_type == "FARGATE" ? 1 : 0}".


network_configuration {
security_groups = ["${var.sg_webapp_instances_id}"]
subnets = ["${split(",", var.subnet_ids)}"]
}
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For this example, we need to add assign_public_ip = "true" for Fargate (since we don't create NAT). Otherwise, our tasks won't be able to pull Docker image from ECR or public Docker Hub. It will return:

CannotPullContainerError: API error (500): Get https://registry-1.docker.io/v2/: net/http: request canceled while waiting for connection (Client.Timeout exceeded while awaiting headers)

See samuelkarp answer here.

you either need private IP + NAT or a public IP + IGW. In your example, the task that's failing has neither NAT nor a public IP.

Terraform documentation: https://www.terraform.io/docs/providers/aws/r/ecs_service.html#assign_public_ip


load_balancer {
target_group_arn = "${aws_alb_target_group.webapp_tg.arn}"
container_name = "webapp"
container_port = 5000
}

lifecycle {
create_before_destroy = true
}
}

resource "aws_ecs_task_definition" "webapp_definition" {
count = "${var.launch_type == "FARGATE" ? 0 : 1}"
family = "${var.name_prefix}_webapp"
container_definitions = "${data.template_file.task_webapp.rendered}"

lifecycle {
create_before_destroy = true
}
}

resource "aws_ecs_task_definition" "webapp_definition_fargate" {
count = "${var.launch_type == "FARGATE" ? 1 : 0}"
family = "${var.name_prefix}_webapp"
container_definitions = "${data.template_file.task_webapp.rendered}"
requires_compatibilities = ["FARGATE"]
network_mode = "awsvpc"
execution_role_arn = "${var.ecs_task_execution_role}"
cpu = "512"
memory = "1024"

lifecycle {
create_before_destroy = true
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12 changes: 10 additions & 2 deletions asg/vars.tf
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Expand Up @@ -24,6 +24,7 @@ variable "ecs_image_id" {
us-west-1 = "ami-9ad4dcfa"
us-west-2 = "ami-92e06fea"
}
description = "ECS Optimized AMI. Not used with launch_type FARGATE."
}

variable "webapp_docker_image_name" {
Expand All @@ -43,7 +44,12 @@ variable "count_webapp" {

variable "desired_capacity_on_demand" {
default = 2
description = "Number of instance to run"
description = "Number of instances to run. Not used with launch_type FARGATE"
}

variable "launch_type" {
default = "EC2"
description = "launch type. set to FARGATE to use fargate. default is EC2 launch type."
}

variable "ec2_key_name" {
Expand All @@ -53,7 +59,7 @@ variable "ec2_key_name" {

variable "instance_type" {
default = "t2.micro"
description = "EC2 instance type to use"
description = "EC2 instance type to use. Not used with launch_type FARGATE"
}

variable "minimum_healthy_percent_webapp" {
Expand All @@ -70,6 +76,8 @@ variable "subnet_ids" {}
/* Consume static outputs */
variable "ecs_instance_profile" {}
variable "ecs_service_role" {}
variable "ecs_task_execution_role" {}


/* Region settings for AWS provider */
provider "aws" {
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48 changes: 48 additions & 0 deletions static/iam/iam.tf
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Expand Up @@ -104,3 +104,51 @@ resource "aws_iam_role_policy" "ecs_service_role_policy" {
}
EOF
}

/**
* Role for ECS using Fargate to use awslogs and access ECR registry
*/

resource "aws_iam_role" "ecs_task_execution_role" {
name = "${var.name_prefix}_ecs_task_execution_role"
assume_role_policy = <<EOF
{
"Version": "2012-10-17",
"Statement": [
{
"Sid": "",
"Effect": "Allow",
"Principal": {
"Service": "ecs-tasks.amazonaws.com"
},
"Action": "sts:AssumeRole"
}
]
}
EOF
}

resource "aws_iam_role_policy" "ecs_task_execution_role_policy" {
name = "${var.name_prefix}ecs_task_execution_role_policy"
role = "${aws_iam_role.ecs_task_execution_role.id}"

policy = <<EOF
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": [
"ecr:GetAuthorizationToken",
"ecr:BatchCheckLayerAvailability",
"ecr:GetDownloadUrlForLayer",
"ecr:BatchGetImage",
"logs:CreateLogStream",
"logs:PutLogEvents"
],
"Resource": "*"
}
]
}
EOF
}
4 changes: 4 additions & 0 deletions static/iam/output.tf
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Expand Up @@ -9,3 +9,7 @@ output "ecs_instance_profile" {
output "ecs_service_role" {
value = "${aws_iam_role.ecs_service_role.name}"
}

output "ecs_task_execution_role" {
value = "${aws_iam_role.ecs_task_execution_role.arn}"
}