ECS Services and Scheduling

While task definitions tell ECS what to run, services tell ECS how many to run and how to keep them running. An ECS service is a long-running configuration that maintains a specified number of task instances, replaces failed tasks, and integrates with load balancers and auto-scaling. This lesson covers services, scheduling strategies, deployments, and auto-scaling.

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What Is an ECS Service?

An ECS service ensures that a desired number of tasks are running at all times. If a task fails, crashes, or is stopped, the service scheduler automatically launches a replacement.

Service: my-web-app (desired count: 3)

  +--------+    +--------+    +--------+
  | Task 1 |    | Task 2 |    | Task 3 |
  | (v1.0) |    | (v1.0) |    | (v1.0) |
  +--------+    +--------+    +--------+
       ↑             ↑             ↑
       └─────────────┼─────────────┘
                     |
              Service Scheduler
              "Keep 3 running"

Key Service Properties