AWS ECS(Task)

Task

• Instanciated task definiton
• Running docker instances (containers) specified in definition
  • One ore more containers on tsk
• Entire task is run on a single Container Instance
• Two tasks (from the same definition) may run on different container instances 

Task Definition

• JSON representation of a docker run CMD
• Required to run Docker container
• Grouping of related containers that run together e.g.
  • container: wordpress (PHP)
  • container: mysql
• Each container in the group lands on the same instance
• If you use the same name ECS versions it and always uses the latest
• Must be registered with ECS

Task Definition (structure)

• Family
  • Name of the task definiton - can have revisions
• Container Definitions
  • basic
    • name - can be used is links section
    • image - url to repository
    • memory  - at least 4MiB
    • port mappings - bridge container host port with container port
      • hostPort -> containerPort
      • protocol 
  • advanced
    • cpu - sharing CPU
    • essential - should failed container terminate the whole task
    • links - allows 2 containers to communicate without port mappings
    • ...
• Volumes
  • Data volumes to be attached to container
  • Volumes are associated with container instance
  • Use cases
    • persistence (container disks are ephemeral)
    • Sharing scratch area