A Fargate Task Definition

Fargate task definitions require awsvpc networking and specific CPU/memory values.

Fargate task definitions have a few rules that differ from EC2:

  • requiresCompatibilities must include FARGATE.
  • networkMode must be awsvpc.
  • Task-level cpu and memory are required and must be a valid pair.
  • An executionRoleArn is needed to pull private images and write logs.

Example

Example · json
{
  "family": "api",
  "requiresCompatibilities": [
    "FARGATE"
  ],
  "networkMode": "awsvpc",
  "cpu": "512",
  "memory": "1024",
  "executionRoleArn": "arn:aws:iam::123456789012:role/ecsTaskExecutionRole",
  "containerDefinitions": [
    {
      "name": "api",
      "image": "123456789012.dkr.ecr.us-east-1.amazonaws.com/api:7",
      "essential": true,
      "portMappings": [
        {
          "containerPort": 8080
        }
      ]
    }
  ]
}

When to use it

  • A developer writes a Fargate task definition specifying awsvpc networking and exact CPU/memory values so ECS can validate it at registration time.
  • A team sets the Fargate platform version in their task definition to lock the underlying kernel version for a compliance audit.
  • An ops engineer adds an ephemeralStorage field to a Fargate task definition to give a data-processing container 50 GB of scratch space.

More examples

Minimal Fargate Task Definition

A complete Fargate task definition requiring awsvpc network mode, valid CPU/memory combination, and an execution role ARN.

Example · json
{
  "family": "fargate-api",
  "networkMode": "awsvpc",
  "requiresCompatibilities": ["FARGATE"],
  "cpu": "512",
  "memory": "1024",
  "executionRoleArn": "arn:aws:iam::123456789012:role/ecsTaskExecutionRole",
  "containerDefinitions": [
    {
      "name": "api",
      "image": "123456789012.dkr.ecr.us-east-1.amazonaws.com/api:v3",
      "portMappings": [{"containerPort": 8080}],
      "essential": true
    }
  ]
}

Add Expanded Ephemeral Storage

Adds 50 GiB of ephemeral scratch storage to a Fargate task, beyond the default 20 GiB, for large data-processing workloads.

Example · json
{
  "family": "data-processor",
  "networkMode": "awsvpc",
  "requiresCompatibilities": ["FARGATE"],
  "cpu": "1024",
  "memory": "4096",
  "ephemeralStorage": {"sizeInGiB": 50},
  "containerDefinitions": [
    {"name": "processor", "image": "my-proc:latest", "essential": true}
  ]
}

Register Fargate Task Def from File

Registers the Fargate task definition JSON and prints the resulting family, revision number, and status to confirm success.

Example · bash
aws ecs register-task-definition \
  --cli-input-json file://fargate-task-def.json \
  --query 'taskDefinition.{family:family,revision:revision,status:status}'

Related

ecs td cpu memoryecs networking awsvpc

Discussion

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