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version: "1.0.1" name: ecs description: AWS ECS container orchestration for running Docker containers. Use when deploying containerized applications, configuring task definitions, setting up services, managing clusters, or troubleshooting container issues. last_updated: "2026-01-07" doc_source: https://docs.aws.amazon.com/AmazonECS/latest/developerguide/

AWS ECS

Amazon Elastic Container Service (ECS) is a fully managed container orchestration service. Run containers on AWS Fargate (serverless) or EC2 instances.

Core Concepts
Common Patterns
CLI Reference
Best Practices
Troubleshooting
References

Core Concepts

Cluster

Logical grouping of tasks or services. Can contain Fargate tasks, EC2 instances, or both.

Task Definition

Blueprint for your application. Defines containers, resources, networking, and IAM roles.

Task

Running instance of a task definition. Can run standalone or as part of a service.

Service

Maintains desired count of tasks. Handles deployments, load balancing, and auto scaling.

Launch Types

Type	Description	Use Case
Fargate	Serverless, pay per task	Most workloads
EC2	Self-managed instances	GPU, Windows, specific requirements

Common Patterns

Create a Fargate Cluster

AWS CLI:

bash

# Create cluster
aws ecs create-cluster --cluster-name my-cluster
 
# With capacity providers
aws ecs create-cluster \
  --cluster-name my-cluster \
  --capacity-providers FARGATE FARGATE_SPOT \
  --default-capacity-provider-strategy \
    capacityProvider=FARGATE,weight=1 \
    capacityProvider=FARGATE_SPOT,weight=1

Register Task Definition

bash

cat > task-definition.json << 'EOF'
{
  "family": "web-app",
  "networkMode": "awsvpc",
  "requiresCompatibilities": ["FARGATE"],
  "cpu": "256",
  "memory": "512",
  "executionRoleArn": "arn:aws:iam::123456789012:role/ecsTaskExecutionRole",
  "taskRoleArn": "arn:aws:iam::123456789012:role/ecsTaskRole",
  "containerDefinitions": [
    {
      "name": "web",
      "image": "123456789012.dkr.ecr.us-east-1.amazonaws.com/my-app:latest",
      "portMappings": [
        {
          "containerPort": 8080,
          "protocol": "tcp"
        }
      ],
      "environment": [
        {"name": "NODE_ENV", "value": "production"}
      ],
      "secrets": [
        {
          "name": "DB_PASSWORD",
          "valueFrom": "arn:aws:secretsmanager:us-east-1:123456789012:secret:db-password"
        }
      ],
      "logConfiguration": {
        "logDriver": "awslogs",
        "options": {
          "awslogs-group": "/ecs/web-app",
          "awslogs-region": "us-east-1",
          "awslogs-stream-prefix": "ecs",
          "mode": "non-blocking",
          "max-buffer-size": "25m"
        }
      },
      "healthCheck": {
        "command": ["CMD-SHELL", "curl -f http://localhost:8080/health || exit 1"],
        "interval": 30,
        "timeout": 5,
        "retries": 3,
        "startPeriod": 60
      }
    }
  ]
}
EOF
 
aws ecs register-task-definition --cli-input-json file://task-definition.json

Create Service with Load Balancer

bash

aws ecs create-service \
  --cluster my-cluster \
  --service-name web-service \
  --task-definition web-app:1 \
  --desired-count 2 \
  --launch-type FARGATE \
  --network-configuration "awsvpcConfiguration={
    subnets=[subnet-12345678,subnet-87654321],
    securityGroups=[sg-12345678],
    assignPublicIp=DISABLED
  }" \
  --load-balancers "targetGroupArn=arn:aws:elasticloadbalancing:us-east-1:123456789012:targetgroup/web-tg/1234567890123456,containerName=web,containerPort=8080" \
  --health-check-grace-period-seconds 60 \
  --deployment-configuration "deploymentCircuitBreaker={enable=true,rollback=true}"

Run Standalone Task

bash

aws ecs run-task \
  --cluster my-cluster \
  --task-definition my-batch-job:1 \
  --launch-type FARGATE \
  --network-configuration "awsvpcConfiguration={
    subnets=[subnet-12345678],
    securityGroups=[sg-12345678],
    assignPublicIp=ENABLED
  }"

Update Service (Deploy New Image)

bash

# Register new task definition with updated image
aws ecs register-task-definition --cli-input-json file://task-definition.json
 
# Update service to use new version
aws ecs update-service \
  --cluster my-cluster \
  --service web-service \
  --task-definition web-app:2 \
  --force-new-deployment

Fargate Spot with SQS-Based Scaling

Use FARGATE_SPOT for batch/queue workloads to cut costs ~70%. Always include a fallback to regular FARGATE.

bash

# Create service with Spot + fallback
aws ecs create-service \
  --cluster batch-cluster \
  --service-name queue-processor \
  --task-definition my-processor:1 \
  --desired-count 0 \
  --capacity-provider-strategy \
    capacityProvider=FARGATE_SPOT,weight=4,base=0 \
    capacityProvider=FARGATE,weight=1,base=1 \
  --network-configuration "awsvpcConfiguration={
    subnets=[subnet-12345678],
    securityGroups=[sg-12345678],
    assignPublicIp=DISABLED
  }"
 
# Register scalable target (scale to zero when queue empty)
aws application-autoscaling register-scalable-target \
  --service-namespace ecs \
  --resource-id service/batch-cluster/queue-processor \
  --scalable-dimension ecs:service:DesiredCount \
  --min-capacity 0 \
  --max-capacity 20
 
# Scale-out alarm: messages > 100
aws cloudwatch put-metric-alarm \
  --alarm-name queue-scale-out \
  --metric-name ApproximateNumberOfMessagesVisible \
  --namespace AWS/SQS \
  --dimensions Name=QueueName,Value=my-queue \
  --statistic Average \
  --period 60 \
  --evaluation-periods 1 \
  --threshold 100 \
  --comparison-operator GreaterThanThreshold \
  --alarm-actions <scale-out-policy-arn>
 
# Scale-in alarm: queue empty for 3 periods (conservative to avoid flapping)
aws cloudwatch put-metric-alarm \
  --alarm-name queue-scale-in \
  --metric-name ApproximateNumberOfMessagesVisible \
  --namespace AWS/SQS \
  --dimensions Name=QueueName,Value=my-queue \
  --statistic Average \
  --period 60 \
  --evaluation-periods 3 \
  --threshold 0 \
  --comparison-operator LessThanOrEqualToThreshold \
  --alarm-actions <scale-in-policy-arn>

Fargate Spot interruption handling: Spot tasks receive a SIGTERM 2 minutes before termination. Catch it in your application for graceful shutdown. For SQS consumers, call ChangeMessageVisibility on in-flight messages so they return to the queue rather than timing out.

Auto Scaling

bash

# Register scalable target
aws application-autoscaling register-scalable-target \
  --service-namespace ecs \
  --resource-id service/my-cluster/web-service \
  --scalable-dimension ecs:service:DesiredCount \
  --min-capacity 2 \
  --max-capacity 10
 
# Target tracking policy
aws application-autoscaling put-scaling-policy \
  --service-namespace ecs \
  --resource-id service/my-cluster/web-service \
  --scalable-dimension ecs:service:DesiredCount \
  --policy-name cpu-target-tracking \
  --policy-type TargetTrackingScaling \
  --target-tracking-scaling-policy-configuration '{
    "TargetValue": 70.0,
    "PredefinedMetricSpecification": {
      "PredefinedMetricType": "ECSServiceAverageCPUUtilization"
    },
    "ScaleOutCooldown": 60,
    "ScaleInCooldown": 120
  }'

CLI Reference

Cluster Management

Command	Description
`aws ecs create-cluster`	Create cluster
`aws ecs describe-clusters`	Get cluster details
`aws ecs list-clusters`	List clusters
`aws ecs delete-cluster`	Delete cluster

Task Definitions

Command	Description
`aws ecs register-task-definition`	Create task definition
`aws ecs describe-task-definition`	Get task definition
`aws ecs list-task-definitions`	List task definitions
`aws ecs deregister-task-definition`	Deregister version

Services

Command	Description
`aws ecs create-service`	Create service
`aws ecs update-service`	Update service
`aws ecs describe-services`	Get service details
`aws ecs delete-service`	Delete service

Tasks

Command	Description
`aws ecs run-task`	Run standalone task
`aws ecs stop-task`	Stop running task
`aws ecs describe-tasks`	Get task details
`aws ecs list-tasks`	List tasks

Best Practices

Security

Use task roles for AWS API access (not access keys)
Use execution roles for ECR/Secrets access
Store secrets in Secrets Manager or Parameter Store
Use private subnets with NAT gateway
Enable CloudTrail for API auditing

Performance

Right-size CPU/memory — monitor and adjust
Use Fargate Spot for fault-tolerant workloads (70% savings)
Enable container insights for monitoring
Use service discovery for internal communication

Reliability

Deploy across multiple AZs
Configure health checks properly
Set appropriate deregistration delay
Use circuit breaker for deployments

bash

aws ecs update-service \
  --cluster my-cluster \
  --service web-service \
  --deployment-configuration '{
    "deploymentCircuitBreaker": {
      "enable": true,
      "rollback": true
    }
  }'

Cost Optimization

Use Fargate Spot for batch workloads
Right-size task resources
Scale to zero when not needed
Use capacity providers for mixed Fargate/Spot

Troubleshooting

Task Fails to Start

Check:

bash

# View stopped tasks
aws ecs describe-tasks \
  --cluster my-cluster \
  --tasks $(aws ecs list-tasks --cluster my-cluster --desired-status STOPPED --query 'taskArns[0]' --output text)

Common causes:

Image not found (ECR permissions)
Secrets access denied
Network configuration (subnets, security groups)
Resource limits exceeded

Container Keeps Restarting

Debug:

bash

# Check CloudWatch logs
aws logs get-log-events \
  --log-group-name /ecs/web-app \
  --log-stream-name "ecs/web/abc123"
 
# Check task details
aws ecs describe-tasks \
  --cluster my-cluster \
  --tasks task-arn \
  --query 'tasks[0].containers[0].{reason:reason,exitCode:exitCode}'

Causes:

Health check failing
Application crashing
Out of memory

Live Debugging with ECS Exec

Connect directly to a running container without SSH. Requires enableExecuteCommand: true on the service and the SSM agent in your container image (included in most base images).

bash

# Enable on existing service
aws ecs update-service \
  --cluster my-cluster \
  --service web-service \
  --enable-execute-command
 
# Get a shell in a running task
TASK_ARN=$(aws ecs list-tasks --cluster my-cluster --service-name web-service \
  --query 'taskArns[0]' --output text)
 
aws ecs execute-command \
  --cluster my-cluster \
  --task $TASK_ARN \
  --container web \
  --interactive \
  --command "/bin/sh"

Requirements: Task role must have ssmmessages:CreateControlChannel, ssmmessages:CreateDataChannel, ssmmessages:OpenControlChannel, ssmmessages:OpenDataChannel permissions.

Service Stuck Deploying

bash

# Check deployment status
aws ecs describe-services \
  --cluster my-cluster \
  --services web-service \
  --query 'services[0].deployments'
 
# Check events
aws ecs describe-services \
  --cluster my-cluster \
  --services web-service \
  --query 'services[0].events[:5]'

Causes:

Health check failing on new tasks
Not enough capacity
Target group health checks failing

Cannot Pull Image from ECR

Check execution role has:

json

{
  "Effect": "Allow",
  "Action": [
    "ecr:GetAuthorizationToken",
    "ecr:BatchCheckLayerAvailability",
    "ecr:GetDownloadUrlForLayer",
    "ecr:BatchGetImage"
  ],
  "Resource": "*"
}

Also check:

VPC endpoint for ECR (if private subnet)
NAT gateway (if private subnet)
Security group allows HTTPS outbound

References

← v1.0.0 All versions

Skill v1.0.1

AWS ECS

Table of Contents

Core Concepts

Cluster

Task Definition

Task

Service

Launch Types

Common Patterns

Create a Fargate Cluster

Register Task Definition

Create Service with Load Balancer

Run Standalone Task

Update Service (Deploy New Image)

Fargate Spot with SQS-Based Scaling

Auto Scaling

CLI Reference

Cluster Management

Task Definitions

Services

Tasks

Best Practices

Security

Performance

Reliability

Cost Optimization

Troubleshooting

Task Fails to Start

Container Keeps Restarting

Live Debugging with ECS Exec

Service Stuck Deploying

Cannot Pull Image from ECR

References