ECS (Elastic Container Service)

• ECS = Elastic Container Service
• Launch Docker containers on AWS
• You must provision & maintain the infrastructure (the EC2 instances)
• AWS takes care of starting / stopping containers
• Has integrations with the Application Load Balancer

Launch Types

EC2 Launch Type

• Launch Docker containers on AWS = Launch ECS Tasks on ECS Clusters
• EC2 Launch Type: you must provision & maintain the infrastructure (the EC2 instances)
• Each EC2 Instance must run the ECS Agent to register in the ECS Cluster
• AWS takes care of starting / stopping containers

Fargate Launch Type

• Launch Docker containers on AWS
• You do not provision the infrastructure(no EC2 instances to manage)
• It’s all Serverless!
• You just create task definitions
• AWS just runs ECS Tasks for you based on the CPU / RAM you need
• To scale, just increase the number of tasks. Simple - no more EC2 instances

IAM Roles for ECS

• EC2 Instance Profile (EC2 Launch Type only):
  • Used by the ECS agent
  • Makes API calls to ECS service
  • Send container logs to CloudWatch Logs
  • Pull Docker image from ECR
  • Reference sensitive data in Secrets Manager or SSM Parameter Store
• ECS Task Role:
  • Allows each task to have a specific role
  • Use different roles for the different ECS Services you run
  • Task Role is defined in the task definition

Load Balancing Integration

• Application Load Balancer supported and works for most use cases
• Network Load Balancer recommended only for high throughput / high performance use cases, or to pair it with AWS Private Link
• Classic Load Balancer supported but not recommended (no advanced features - no Fargate)

Data Volumes

• Mount EFS file systems onto ECS tasks
• Works for both EC2 and Fargate launch types
• Tasks running in any AZ will share the same data in the EFS file system
• Fargate + EFS = Serverless
• Use cases: persistent multi-AZ shared storage for your containers
• Note:
• Amazon S3 cannot be mounted as a file system

ECS Service Auto Scaling

• Automatically increase/decrease the desired number of ECS tasks
• Amazon ECS Auto Scaling uses AWS Application Auto Scaling
  • ECS Service Average CPU Utilization
  • ECS Service Average Memory Utilization - Scale on RAM
  • ALB Request Count Per Target – metric coming from the ALB
• Target Tracking – scale based on target value for a specific CloudWatch metric
• Step Scaling – scale based on a specified CloudWatch Alarm
• Scheduled Scaling – scale based on a specified date/time (predictable changes)
• ECS Service Auto Scaling (task level) ≠ EC2 Auto Scaling (EC2 instance level)
• Fargate Auto Scaling is much easier to setup (because Serverless)

EC2 Launch Type – Auto Scaling EC2 Instances

• Accommodate ECS Service Scaling by adding underlying EC2 Instances
• Auto Scaling Group Scaling
  • Scale your ASG based on CPU Utilization
  • Add EC2 instances over time
• ECS Cluster Capacity Provider
  • Used to automatically provision and scale the infrastructure for your ECS Tasks
  • Capacity Provider paired with an Auto Scaling Group
  • Add EC2 Instances when you’re missing capacity (CPU, RAM…)

ECS tasks invoked by Event Bridge