ECS

  • Elastic Container Service
  • Run docker containers in EC2 machines
  • Components
  • ECS Core provision EC2 instance to run docker container
  • Fargate run ECS task to AWS Provide Compute, more serverless than ECS Core
  • EKS is Elastic Kubernetes Service by AWS
  • ECR is Elastic Container Registry by AWS
  • IAM Security and Roles are in ECS Task level
  • ECS can enable dynamic port mapping with
  • ALB
  • NLB
  • ECS setup
  • For regular EC2 Instance install the ECS Agent and edit config file
  • For ECS ready Linux AMI, no need to install ECS Agent, only edit the config file
  • Editing the config file
    • Location /etc/ecs/ecs.config
    • There are 35 Configuration to edit
    • ECS CLUSTER
    • ECS_ENGINE_AUTH_DATA
    • ECS_AVAILABLE_LOGGING_DRIVER
    • ECS_ENABLE_TASK_IAM_ROLE
  • If the associated ec2 instances are in stopped state and we terminate ecs, it will not be de-registered automatically
  • When ecs client is stopped, the instance remain active with agent connection status false
  • Cluster name is set up in /etc/ecs/ecs.config file

ECS Components

  • Task Definition: Allow port mapping. Port Mapping allows the container to send and receive traffic through the host machine
  • Service Schedular: Allow to run tasks manually
  • Container Instance: On which the container runs on, typically the ec2 instance or ecs ready ec2 instance
  • Container Agent: Allows the containers to connect with the cluster

Task Placement Strategy

Determine how the tasks will be placed between instances. ECS supports 3 types of Task Placement Strategies

  1. binpack: Placed task by using least amount of CPU or memory. This minimize the number of instances are being used
  2. random: Place tasks randomly. Make sure tasks are scheduled in instances with enough resources.
  3. spread: Placed tasks based on specified value (key-value pairs, instanceId or host). For example, if the field is instanceId the task will be distributed evenly in different instances. Another example, if the field is az, the tasks will be evenly distributed among availability zones.

When a container requires to listen to specic port,

  • Specify the port for the container
  • Put 0 as the host port

In this case, the ECS will automatically assign the port.

Cluster Query Language

  • Allow more fine grained way to place tasks

Using environment variables

  • Use advanced task definition
  • Define environment parameters under the task definition environment variables