AWS ECS: Update a Service (Deploy New Version)

Q: AWS ECS: Update a Service (Deploy New Version)

## Updating ECS Services The aws ecs update-service command modifies an existing ECS service, most commonly to deploy a new version of a task definition. ECS performs a rolling deployment by default. ### Deploy a New Task Definition bash aws ecs update-service \ --cluster production-cluster \ --service api-service \ --task-definition api-task:42 This tells ECS to gradually replace running tasks with tasks using version 42 of the api-task task definition. ### Force New Deployment (sam

Deploy a new task definition version to an ECS service using aws ecs update-service with rolling deployment and force new deployment options.

ECS Operations

Detailed Explanation

Updating ECS Services

The aws ecs update-service command modifies an existing ECS service, most commonly to deploy a new version of a task definition. ECS performs a rolling deployment by default.

Deploy a New Task Definition

aws ecs update-service \
  --cluster production-cluster \
  --service api-service \
  --task-definition api-task:42

This tells ECS to gradually replace running tasks with tasks using version 42 of the api-task task definition.

Force New Deployment (same version)

aws ecs update-service \
  --cluster production-cluster \
  --service api-service \
  --force-new-deployment

Forces ECS to stop and restart all tasks even if the task definition has not changed. Useful when:

Your container image tag (latest) was updated
You need to pick up new secrets or config
Tasks are in an unhealthy state

Scale the Service

aws ecs update-service \
  --cluster production-cluster \
  --service api-service \
  --desired-count 4

Combined Deployment

aws ecs update-service \
  --cluster production-cluster \
  --service api-service \
  --task-definition api-task:43 \
  --desired-count 3 \
  --force-new-deployment

Monitor the Deployment

aws ecs describe-services \
  --cluster production-cluster \
  --services api-service \
  --query "services[0].deployments[].[status,desiredCount,runningCount,taskDefinition]" \
  --output table

Example Output

---------------------------------------------------------
|                   DescribeServices                     |
+---------+------+---------+----------------------------+
| PRIMARY |  3   |    2    | arn:...:api-task:43        |
| ACTIVE  |  3   |    1    | arn:...:api-task:42        |
+---------+------+---------+----------------------------+

During a rolling deployment, you will see both the PRIMARY (new) and ACTIVE (old) deployments until all tasks are replaced.

Wait for Stable

aws ecs wait services-stable \
  --cluster production-cluster \
  --services api-service

This blocks until the service reaches a steady state (all tasks running the latest task definition).

Use Case

Deploying new application versions to ECS Fargate or EC2 services, scaling container workloads, performing zero-downtime rolling deployments, or forcing task restarts to pick up configuration changes.

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