AWS ECS & Fargate

Run containerized applications on Amazon ECS with Fargate serverless compute or EC2 launch type.

When to Use This Skill

• Deploying Docker containers to AWS without managing servers (Fargate)
• Running microservices with service discovery and load balancing
• Setting up blue/green or rolling deployments for containerized apps
• Configuring auto-scaling for container workloads
• Migrating from docker-compose or Kubernetes to ECS
• Troubleshooting task failures, health check issues, or networking problems

Prerequisites

• AWS CLI v2 installed and configured
• Docker installed for building and pushing images
• IAM permissions: ecs:*, ecr:*, elasticloadbalancing:*, logs:*, iam:PassRole
• An ECR repository for storing container images
• A VPC with subnets and an ALB (see aws-vpc (aws-vpc))

Cluster Setup

# Create an ECS cluster with Container Insights enabled
aws ecs create-cluster \
  --cluster-name production \
  --capacity-providers FARGATE FARGATE_SPOT \
  --default-capacity-provider-strategy '[
    {"capacityProvider": "FARGATE", "weight": 1, "base": 2},
    {"capacityProvider": "FARGATE_SPOT", "weight": 3}
  ]' \
  --settings '[{"name": "containerInsights", "value": "enabled"}]'

# List clusters
aws ecs list-clusters

# Describe cluster details
aws ecs describe-clusters --clusters production --include STATISTICS ATTACHMENTS

Push Image to ECR

# Create ECR repository
aws ecr create-repository \
  --repository-name myapp \
  --image-scanning-configuration scanOnPush=true \
  --encryption-configuration encryptionType=KMS

# Authenticate Docker to ECR
aws ecr get-login-password --region us-east-1 | \
  docker login --username AWS --password-stdin 123456789012.dkr.ecr.us-east-1.amazonaws.com

# Build, tag, and push
docker build -t myapp:latest .
docker tag myapp:latest 123456789012.dkr.ecr.us-east-1.amazonaws.com/myapp:latest
docker push 123456789012.dkr.ecr.us-east-1.amazonaws.com/myapp:latest

Task Definition

{
  "family": "myapp",
  "networkMode": "awsvpc",
  "requiresCompatibilities": ["FARGATE"],
  "cpu": "512",
  "memory": "1024",
  "executionRoleArn": "arn:aws:iam::123456789012:role/ecsTaskExecutionRole",
  "taskRoleArn": "arn:aws:iam::123456789012:role/ecsTaskRole",
  "containerDefinitions": [
    {
      "name": "myapp",
      "image": "123456789012.dkr.ecr.us-east-1.amazonaws.com/myapp:latest",
      "essential": true,
      "portMappings": [
        {
          "containerPort": 8080,
          "protocol": "tcp"
        }
      ],
      "environment": [
        {"name": "NODE_ENV", "value": "production"},
        {"name": "PORT", "value": "8080"}
      ],
      "secrets": [
        {
          "name": "DB_PASSWORD",
          "valueFrom": "arn:aws:secretsmanager:us-east-1:123456789012:secret:myapp/db-password"
        },
        {
          "name": "API_KEY",
          "valueFrom": "arn:aws:ssm:us-east-1:123456789012:parameter/myapp/api-key"
        }
      ],
      "healthCheck": {
        "command": ["CMD-SHELL", "curl -f http://localhost:8080/health || exit 1"],
        "interval": 30,
        "timeout": 5,
        "retries": 3,
        "startPeriod": 60
      },
      "logConfiguration": {
        "logDriver": "awslogs",
        "options": {
          "awslogs-group": "/ecs/myapp",
          "awslogs-region": "us-east-1",
          "awslogs-stream-prefix": "ecs",
          "awslogs-create-group": "true"
        }
      },
      "ulimits": [
        {"name": "nofile", "softLimit": 65536, "hardLimit": 65536}
      ]
    }
  ]
}

# Register the task definition
aws ecs register-task-definition --cli-input-json file://task-definition.json

# List task definition revisions
aws ecs list-task-definitions --family-prefix myapp

# Deregister an old revision
aws ecs deregister-task-definition --task-definition myapp:1

Create Service with ALB

# Create the CloudWatch log group first
aws logs create-log-group --log-group-name /ecs/myapp
aws logs put-retention-policy --log-group-name /ecs/myapp --retention-in-days 30

# Create ECS service with load balancer
aws ecs create-service \
  --cluster production \
  --service-name myapp \
  --task-definition myapp:2 \
  --desired-count 3 \
  --launch-type FARGATE \
  --platform-version LATEST \
  --deployment-configuration '{
    "deploymentCircuitBreaker": {"enable": true, "rollback": true},
    "maximumPercent": 200,
    "minimumHealthyPercent": 100
  }' \
  --network-configuration '{
    "awsvpcConfiguration": {
      "subnets": ["subnet-private-a", "subnet-private-b"],
      "securityGroups": ["sg-app"],
      "assignPublicIp": "DISABLED"
    }
  }' \
  --load-balancers '[{
    "targetGroupArn": "arn:aws:elasticloadbalancing:us-east-1:123456789012:targetgroup/myapp-tg/abc123",
    "containerName": "myapp",
    "containerPort": 8080
  }]' \
  --service-registries '[{
    "registryArn": "arn:aws:servicediscovery:us-east-1:123456789012:service/srv-abc123"
  }]' \
  --enable-execute-command \
  --propagate-tags SERVICE

Deployments

# Rolling update - update task definition and force new deployment
aws ecs update-service \
  --cluster production \
  --service myapp \
  --task-definition myapp:3 \
  --force-new-deployment

# Watch deployment progress
aws ecs describe-services \
  --cluster production \
  --services myapp \
  --query "services[0].deployments[].{Status:status,Running:runningCount,Desired:desiredCount,TaskDef:taskDefinition}" \
  --output table

# Wait for service to stabilize
aws ecs wait services-stable --cluster production --services myapp

# Exec into a running container for debugging
aws ecs execute-command \
  --cluster production \
  --task arn:aws:ecs:us-east-1:123456789012:task/production/abc123 \
  --container myapp \
  --interactive \
  --command "/bin/sh"

Auto Scaling

# Register ECS service as a scalable target
aws application-autoscaling register-scalable-target \
  --service-namespace ecs \
  --resource-id service/production/myapp \
  --scalable-dimension ecs:service:DesiredCount \
  --min-capacity 2 \
  --max-capacity 20

# Target tracking policy - scale on CPU utilization
aws application-autoscaling put-scaling-policy \
  --service-namespace ecs \
  --resource-id service/production/myapp \
  --scalable-dimension ecs:service:DesiredCount \
  --policy-name cpu-target-tracking \
  --policy-type TargetTrackingScaling \
  --target-tracking-scaling-policy-configuration '{
    "PredefinedMetricSpecification": {
      "PredefinedMetricType": "ECSServiceAverageCPUUtilization"
    },
    "TargetValue": 70.0,
    "ScaleInCooldown": 300,
    "ScaleOutCooldown": 60
  }'

# Scale on request count per target (ALB)
aws application-autoscaling put-scaling-policy \
  --service-namespace ecs \
  --resource-id service/production/myapp \
  --scalable-dimension ecs:service:DesiredCount \
  --policy-name request-count-tracking \
  --policy-type TargetTrackingScaling \
  --target-tracking-scaling-policy-configuration '{
    "PredefinedMetricSpecification": {
      "PredefinedMetricType": "ALBRequestCountPerTarget",
      "ResourceLabel": "app/my-alb/abc123/targetgroup/myapp-tg/def456"
    },
    "TargetValue": 1000.0,
    "ScaleInCooldown": 300,
    "ScaleOutCooldown": 60
  }'

Terraform ECS Fargate Service

resource "aws_ecs_cluster" "main" {
  name = "production"

  setting {
    name  = "containerInsights"
    value = "enabled"
  }
}

resource "aws_ecs_task_definition" "myapp" {
  family                   = "myapp"
  network_mode             = "awsvpc"
  requires_compatibilities = ["FARGATE"]
  cpu                      = 512
  memory                   = 1024
  execution_role_arn       = aws_iam_role.ecs_execution.arn
  task_role_arn            = aws_iam_role.ecs_task.arn

  container_definitions = jsonencode([{
    name      = "myapp"
    image     = "${aws_ecr_repository.myapp.repository_url}:latest"
    essential = true

    portMappings = [{
      containerPort = 8080
      protocol      = "tcp"
    }]

    logConfiguration = {
      logDriver = "awslogs"
      options = {
        awslogs-group         = aws_cloudwatch_log_group.myapp.name
        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
    }
  }])
}

resource "aws_ecs_service" "myapp" {
  name            = "myapp"
  cluster         = aws_ecs_cluster.main.id
  task_definition = aws_ecs_task_definition.myapp.arn
  desired_count   = 3
  launch_type     = "FARGATE"

  deployment_circuit_breaker {
    enable   = true
    rollback = true
  }

  network_configuration {
    subnets          = aws_subnet.private[*].id
    security_groups  = [aws_security_group.app.id]
    assign_public_ip = false
  }

  load_balancer {
    target_group_arn = aws_lb_target_group.myapp.arn
    container_name   = "myapp"
    container_port   = 8080
  }

  enable_execute_command = true
  propagate_tags         = "SERVICE"
}

Viewing Logs

# Tail logs from CloudWatch
aws logs tail /ecs/myapp --follow --since 1h

# Get logs for a specific task
aws logs get-log-events \
  --log-group-name /ecs/myapp \
  --log-stream-name "ecs/myapp/abc123def456" \
  --start-from-head

# Filter logs for errors
aws logs filter-log-events \
  --log-group-name /ecs/myapp \
  --filter-pattern "ERROR" \
  --start-time $(date -d '1 hour ago' +%s000)

Troubleshooting

Problem	Cause	Fix
Task stuck in PROVISIONING	No available capacity in subnets	Check subnet availability and capacity provider
Task fails immediately	Container crashes on startup	Check CloudWatch logs; run image locally first
Health check failing	App not ready within startPeriod	Increase startPeriod; verify health endpoint
Cannot pull ECR image	Execution role missing ECR permissions	Attach AmazonECSTaskExecutionRolePolicy
Service stuck at 0 running	Security group blocks ALB health check	Allow ALB SG to reach container port
Exec command fails	SSM agent not initialized	Ensure enableExecuteCommand is true; check task role
High Fargate costs	Not using Fargate Spot for tolerant workloads	Add FARGATE_SPOT capacity provider
Container OOM killed	Memory limit too low	Increase memory in task definition; check for leaks
Slow deployments	minimumHealthyPercent too high	Set to 50% for faster rolling updates

Related Skills

• docker-management (docker-management) - Container fundamentals
• container-registries (container-registries) - ECR and image management
• aws-vpc (aws-vpc) - Networking for ECS tasks
• aws-iam (aws-iam) - Task and execution roles
• terraform-aws (terraform-aws) - Infrastructure as Code deployment

Limitations

• Infrastructure commands can disrupt services: confirm target host/scope and have backups/snapshots before mutating state.
• Docs-only import: upstream scripts and templates not bundled.