AWS ECS

Overview

• Docker on EC2
• Alternatives
  • Kubernets (K8s)

Model

• ECS - cluster management infrastructure
• Container instance - docker host
  
  • EC2 instance
  • has ECS agent installed
  • has docker deamon installed
  • runs ECS Tasks
• Cluster - pool of resources (CPU/memory/networking) partitioned by containers
  • one or more Container instances
  • it can be scaled-up/down as needed (Auto Scaling)
  • spot fleet integration
• Task
  • See ECS(Task)
• ECS Event Stream
  • Cluster/Task state changes
  • Uses CloudWatch

AWS Fargate

• Managed cluster management
• AWS worries about EC2 resources (cluster)
• All other ECS gurantees remain in place

ECS (Scheduling engine)

• Starts a task
• Based on Blox (open source)
• Types
  • Services
    • "start it and forget it"
    • long running processes (e.g. "MicroService")
    • behind ELB
    • monitors the one that failed and restarts
  • Batch
    • integrates with Spot Fleet
    • basis for AWS Batch
  • Events
    • Triggered based on CloudWatch Event 
  • Daemon
    • Ensures a task is running on every node in the cluster (e.g. monitoring agent)

ECS (Placement Engine)

• When instance joins ECS associates metadata (region, instance type, etc.)
• Selects appropriate container instance capability (cpu, memory, ports)
  • Cluster Constraints (CPU, memory, port)
  • Custom (location, instance type, AMI, custom attributes)
  • Placement Strategies
    • Binpacking
    • Spread (high availability)
    • Affinity (should run together)
      • Anti-affinity (never run together) 
    • Distance instinct (used by Daemon)
  • Placement strategy chaining
    • Spread (Multi-AZ) + Binpack

ECS Agent

• Runs on Container Instance 
• Runs in its own Docker container
• Uses ecs:Poll action to receive commands
• Coordinates deployments
• Possible to query its status

ECR

• EC2 Container Registry
• Fully managed Docker Container Registry

References

• http://www.allthingsdistributed.com/2015/07/under-the-hood-of-the-amazon-ec2-container-service.html