AWS ECS Skill

Deploy containerized applications with ECS and Fargate.

Quick Reference

Attribute	Value
AWS Service	ECS, Fargate
Complexity	Medium-High
Est. Time	20-45 min
Prerequisites	VPC, ECR image, IAM roles

Parameters

Required

Parameter	Type	Description	Validation
cluster_name	string	ECS cluster name	^[a-zA-Z0-9_-]{1,255}$
service_name	string	Service name	^[a-zA-Z0-9_-]{1,255}$
image_uri	string	Container image	ECR or Docker Hub URI
cpu	int	CPU units	256, 512, 1024, 2048, 4096
memory	int	Memory MB	Valid for CPU

Optional

Parameter	Type	Default	Description
desired_count	int	2	Number of tasks
launch_type	string	FARGATE	FARGATE or EC2
platform_version	string	LATEST	Fargate platform version
health_check_path	string	/health	ALB health check path
autoscaling	bool	true	Enable auto-scaling

CPU/Memory Combinations (Fargate)

CPU	Memory Options
256	512, 1024, 2048
512	1024-4096 (1GB increments)
1024	2048-8192 (1GB increments)
2048	4096-16384 (1GB increments)
4096	8192-30720 (1GB increments)

Implementation

Task Definition

{
  "family": "my-app",
  "networkMode": "awsvpc",
  "requiresCompatibilities": ["FARGATE"],
  "cpu": "512",
  "memory": "1024",
  "executionRoleArn": "arn:aws:iam::123456789012:role/ecsTaskExecutionRole",
  "taskRoleArn": "arn:aws:iam::123456789012:role/ecsTaskRole",
  "containerDefinitions": [
    {
      "name": "app",
      "image": "123456789012.dkr.ecr.us-east-1.amazonaws.com/my-app:latest",
      "portMappings": [
        {"containerPort": 8080, "protocol": "tcp"}
      ],
      "essential": true,
      "logConfiguration": {
        "logDriver": "awslogs",
        "options": {
          "awslogs-group": "/ecs/my-app",
          "awslogs-region": "us-east-1",
          "awslogs-stream-prefix": "ecs"
        }
      },
      "healthCheck": {
        "command": ["CMD-SHELL", "curl -f http://localhost:8080/health || exit 1"],
        "interval": 30,
        "timeout": 5,
        "retries": 3,
        "startPeriod": 60
      },
      "secrets": [
        {
          "name": "DB_PASSWORD",
          "valueFrom": "arn:aws:secretsmanager:us-east-1:123456789012:secret:db-password"
        }
      ]
    }
  ]
}

Create Service

aws ecs create-service \
  --cluster prod-cluster \
  --service-name my-service \
  --task-definition my-app:1 \
  --desired-count 2 \
  --launch-type FARGATE \
  --network-configuration '{
    "awsvpcConfiguration": {
      "subnets": ["subnet-111", "subnet-222"],
      "securityGroups": ["sg-xxx"],
      "assignPublicIp": "DISABLED"
    }
  }' \
  --load-balancers '[{
    "targetGroupArn": "arn:aws:elasticloadbalancing:...",
    "containerName": "app",
    "containerPort": 8080
  }]' \
  --deployment-configuration '{
    "maximumPercent": 200,
    "minimumHealthyPercent": 100,
    "deploymentCircuitBreaker": {
      "enable": true,
      "rollback": true
    }
  }'

Auto Scaling

# Register scalable target
aws application-autoscaling register-scalable-target \
  --service-namespace ecs \
  --resource-id service/prod-cluster/my-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/prod-cluster/my-service \
  --scalable-dimension ecs:service:DesiredCount \
  --policy-name cpu-tracking \
  --policy-type TargetTrackingScaling \
  --target-tracking-scaling-policy-configuration '{
    "TargetValue": 70.0,
    "PredefinedMetricSpecification": {
      "PredefinedMetricType": "ECSServiceAverageCPUUtilization"
    },
    "ScaleInCooldown": 300,
    "ScaleOutCooldown": 60
  }'

Troubleshooting

Common Issues

Symptom	Cause	Solution
Task won't start	Image pull failed	Check ECR permissions
Task unhealthy	Health check failing	Increase startPeriod
Service stuck	Deployment circuit breaker	Check task logs
OOM killed	Memory exceeded	Increase memory

Debug Checklist

• Image exists in ECR and accessible?
• Task execution role has permissions?
• Security group allows container port?
• Subnets have NAT for ECR access?
• Secrets Manager accessible?
• Health check path responding?
• Container starts within health check startPeriod?

Task Failure Analysis

# Get stopped task details
aws ecs describe-tasks \
  --cluster prod-cluster \
  --tasks arn:aws:ecs:...:task/xxx \
  --query 'tasks[0].{status:lastStatus,reason:stoppedReason,containers:containers[*].{name:name,reason:reason}}'

Common Stop Reasons

CannotPullContainerError → ECR image or permissions
ResourceInitializationError → Secrets/ENI issue
EssentialContainerExited → Application crash
OutOfMemoryError → Increase memory
HealthCheckFailure → Fix health check

Test Template

def test_ecs_service_healthy():
    # Arrange
    cluster = "prod-cluster"
    service = "my-service"

    # Act
    response = ecs.describe_services(
        cluster=cluster,
        services=[service]
    )

    # Assert
    service_info = response['services'][0]
    assert service_info['status'] == 'ACTIVE'
    assert service_info['runningCount'] >= service_info['desiredCount']
    assert len(service_info['deployments']) == 1  # No pending deployments

Assets

• assets/task-definition.json

  - ECS task definition template

References

• ECS User Guide
• ECS Best Practices