ECS, Fargate, ECR, & EKS

Amazon ECS

Elastic container service. It is Amazon's own container platform. Let you launch container instance and run them.

If you want to launch docker container on AWS you will be launching ECS Tasks. Task definition tells what docker image to use to run the container, how much CPU and RAM are given to each container, and other configuration. The ECS task will be launched within ECS clusters.

ECS clusters can be EC2 launch type or fargate launch type.

EC2 launch type

Your cluster will be comprised of EC2 instance underneath which you have to provision in advance. After your container needs to be running on some kind of host right? In this case you will be running the container in EC2 instances.

In order to make the cluster using EC2 instances, each of the EC2 instances have to run ECS Agent to register itself into the ECS service and cluster that's specified.

Only after you run ECS Agent and regsiter itself will then able to run ECS task. AWS will take care of starting / stopping the containers.

Fargate launch type

This time you don't need to provision any EC2 instance underneath, it is all serverless (although there will be servers underneath but you don't have to worry about it!).

It is still considered a ECS cluster even though it is serverless :)

For fargate launch type you just need to define task definitions, then AWS will run the task for you without having you worrying about allocating the servers. Launch more tasks and it will scale automatically because is serverless!

Launching ECS tasks

When you launch your ECS tasks you get the option to pick which launch type. Either via the EC2 launch type from the cluster you defined. Or via fargate which you don't need to manage the infrastructure yourself. You get to pick it.

IAM for ECS

EC2 instance profile role: This is only for EC2 launch type only because only EC2 launch type have ECS Agent. The profile will be used by ECS agent to make API to ECS service, ECR (for pulling docker images), and CloudWatch for sending logs.

ECS task role: Valid for both fargate and EC2 launch type. This allow each task to have a specific IAM role. This is so that each of your container can have access to different AWS service access. Task A need access to S3, Task B need access to a DynamoDB.

Load balancer integrations

You can expose containers running in clusters in front of a load balancer. ALB is supported.

NLB is only recommended if you need high throughput / high performance or pair it with AWS private link.

Don't use the classic load balancer

Data volumes (EFS)

To have persistent data, because container's data are not saved, you need to use EFS file system. You would mount them in your container in order to save data from the container.

Otherwise, files you write in the container will just be deleted after the container finishes.

EFS is multi-AZ also serverless because you don't have to worry about provisioning the storage it has. Scales automatically.

If you pair it with Fargate + EFS, this is serverless design. Fargate again you do not need to manage the infrastructure that runs the container yourself, it is all serverless. Scales automatically for you.

S3 cannot be used as a mount file system!