AWS Fargate on Amazon ECS

AWS Fargate is a technology that you can use with Amazon ECS to run containers without having to manage servers or clusters of Amazon EC2 instances. With AWS Fargate, you no longer have to provision, configure, or scale clusters of virtual machines to run containers. This removes the need to choose server types, decide when to scale your clusters, or optimize cluster packing.

When you run your tasks and services with the Fargate launch type, you package your application in containers, specify the CPU and memory requirements, define networking and IAM policies, and launch the application. Each Fargate task has its own isolation boundary and does not share the underlying kernel, CPU resources, memory resources, or elastic network interface with another task.

This topic describes the different components of Fargate tasks and services, and calls out special considerations for using Fargate with Amazon ECS.

AWS Fargate with Amazon ECS is currently only available in the following Regions:

Region Name	Region
US East (N. Virginia)	us-east-1
US East (Ohio)	us-east-2
US West (N. California)	us-west-1
US West (Oregon)	us-west-2
Asia Pacific (Mumbai)	ap-south-1
EU (Ireland)	eu-west-1
EU (London)	eu-west-2
EU (Frankfurt)	eu-central-1
Asia Pacific (Tokyo)	ap-northeast-1
Canada (Central)	ca-central-1
Asia Pacific (Seoul)	ap-northeast-2
Asia Pacific (Singapore)	ap-southeast-1
Asia Pacific (Sydney)	ap-southeast-2

The following walkthroughs help you get started using AWS Fargate with Amazon ECS:

Task Definitions

Tasks that use the Fargate launch type do not support all of the task definition parameters that are available. Some parameters are not supported at all, and others behave differently for Fargate tasks.

The following task definition parameters are not valid in Fargate tasks:

disableNetworking
dnsSearchDomains
dnsServers
dockerSecurityOptions
extraHosts
gpu
ipcMode
links
pidMode
placementConstraints
privileged
systemControls

The following task definition parameters are valid in Fargate tasks, but have limitations that should be noted:

linuxParameters – When specifying Linux-specific options that are applied to the container, for capabilities the add parameter is not supported. The devices, sharedMemorySize, and tmpfs parameters are not supported. For more information, see Linux Parameters.
volumes – Fargate tasks only support bind mount host volumes, so the dockerVolumeConfiguration parameter is not supported. For more information, see Volumes.

To ensure that your task definition validates for use with the Fargate launch type, you can specify the following when you register the task definition:

In the AWS Management Console, for the Requires Compatibilities field, specify FARGATE.
In the AWS CLI, specify the --requires-compatibilities option.
In the Amazon ECS API, specify the requiresCompatibilities flag.

Network Mode

Fargate task definitions require that the network mode is set to awsvpc. The awsvpc network mode provides each task with its own elastic network interface. For more information, see Task Networking with the awsvpc Network Mode.

A network configuration is also required when creating a service or manually running tasks. For more information, see Task Networking.

Task CPU and Memory

Fargate task definitions require that you specify CPU and memory at the task level. Although you can also specify CPU and memory at the container level for Fargate tasks, this is optional. Most use cases are satisfied by only specifying these resources at the task level. The table below shows the valid combinations of task-level CPU and memory.

CPU value	Memory value
256 (.25 vCPU)	0.5 GB, 1 GB, 2 GB
512 (.5 vCPU)	1 GB, 2 GB, 3 GB, 4 GB
1024 (1 vCPU)	2 GB, 3 GB, 4 GB, 5 GB, 6 GB, 7 GB, 8 GB
2048 (2 vCPU)	Between 4 GB and 16 GB in 1-GB increments
4096 (4 vCPU)	Between 8 GB and 30 GB in 1-GB increments

Logging

Fargate task definitions only support the awslogs and splunk log drivers for the log configuration.

The awslogs log driver configures your Fargate tasks to send log information to Amazon CloudWatch Logs. The following shows a snippet of a task definition where the awslogs log driver is configured:


"logConfiguration": { 
   "logDriver": "awslogs",
   "options": { 
      "awslogs-group" : "/ecs/fargate-task-definition",
      "awslogs-region": "us-east-1",
      "awslogs-stream-prefix": "ecs"
}

For more information about using the awslogs log driver in a task definition to send your container logs to CloudWatch Logs, see Using the awslogs Log Driver.

For more information about using the splunk log driver in a task definition, see Example: splunk Log Driver.

Amazon ECS Task Execution IAM Role

There is an optional task execution IAM role that you can specify with Fargate to allow your Fargate tasks to make API calls to Amazon ECR. The API calls pull container images as well as calling CloudWatch to store container application logs. For more information, see Amazon ECS Task Execution IAM Role.

Example Task Definition

The following is an example task definition that sets up a web server using the Fargate launch type:


{
   "containerDefinitions": [ 
      { 
         "command": [
            "/bin/sh -c \"echo '<html> <head> <title>Amazon ECS Sample App</title> <style>body {margin-top: 40px; background-color: #333;} </style> </head><body> <div style=color:white;text-align:center> <h1>Amazon ECS Sample App</h1> <h2>Congratulations!</h2> <p>Your application is now running on a container in Amazon ECS.</p> </div></body></html>' >  /usr/local/apache2/htdocs/index.html && httpd-foreground\""
         ],
         "entryPoint": [
            "sh",
            "-c"
         ],
         "essential": true,
         "image": "httpd:2.4",
         "logConfiguration": { 
            "logDriver": "awslogs",
            "options": { 
               "awslogs-group" : "/ecs/fargate-task-definition",
               "awslogs-region": "us-east-1",
               "awslogs-stream-prefix": "ecs"
            }
         },
         "name": "sample-fargate-app",
         "portMappings": [ 
            { 
               "containerPort": 80,
               "hostPort": 80,
               "protocol": "tcp"
            }
         ]
      }
   ],
   "cpu": "256",
   "executionRoleArn": "arn:aws:iam::012345678910:role/ecsTaskExecutionRole",
   "family": "fargate-task-definition",
   "memory": "512",
   "networkMode": "awsvpc",
   "requiresCompatibilities": [ 
       "FARGATE" 
    ]
}

Task Storage

When provisioned, each Fargate task receives the following storage. Task storage is ephemeral. After a Fargate task stops, the storage is deleted.

10 GB of Docker layer storage
An additional 4 GB for volume mounts. This can be mounted and shared among containers using the volumes, mountPoints, and volumesFrom parameters in the task definition.

Note

The host and sourcePath parameters are not supported.

For more information about Amazon ECS default service limits, see Amazon ECS Service Limits.

The following shows a snippet of a task definition where two containers are sharing a single volume:


{
   "containerDefinitions": [ 
      { 
         "image": "my-repo/database",
         "mountPoints": [ 
            { 
               "containerPath": "/var/scratch",
               "sourceVolume": "database_scratch"
            }
         ],
         "name": "database1",
      },
      { 
         "image": "my-repo/database",
         "mountPoints": [ 
            { 
               "containerPath": "/var/scratch",
               "sourceVolume": "database_scratch"
            }
         ],
         "name": "database2",
      }
   ],
   "volumes": [ 
      { 
         "name": "database_scratch"
      }
   ]
}

Tasks and Services

After you have your Fargate task definition prepared, there are some decisions to make when creating your service.

Task Networking

Tasks using the Fargate launch type require the awsvpc network mode, which provides each task with an elastic network interface. When you run a task or create a service with this network mode, you must specify one or more subnets to attach the network interface and one or more security groups to apply to the network interface.

If you are using public subnets, decide whether to provide a public IP address for the network interface. For a Fargate task in a public subnet to pull container images, a public IP address needs to be assigned to the task's elastic network interface, with a route to the internet or a NAT gateway that can route requests to the internet. For a Fargate task in a private subnet to pull container images, the private subnet requires a NAT gateway be attached to route requests to the internet. For more information, see Task Networking with the awsvpc Network Mode.

The following is an example of the networkConfiguration section for a Fargate service:


"networkConfiguration": { 
   "awsvpcConfiguration": { 
      "assignPublicIp": "ENABLED",
      "securityGroups": [ "sg-12345678" ],
      "subnets": [ "subnet-12345678" ]
   }
}

Services with tasks that use the awsvpc network mode (for example, those with the Fargate launch type) only support Application Load Balancers and Network Load Balancers. Classic Load Balancers are not supported. Also, when you create any target groups for these services, you must choose ip as the target type, not instance. This is because tasks that use the awsvpc network mode are associated with an elastic network interface, not an Amazon EC2 instance. For more information, see Service Load Balancing.

Private Registry Authentication

Fargate tasks can authenticate with private image registries, including Docker Hub, using basic authentication. When you enable private registry authentication, you can use private Docker images in your task definitions.

To use private registry authentication, you create a secret with AWS Secrets Manager containing the credentials for your private registry. Then, within your container definition, you specify repositoryCredentials with the full ARN of the secret that you created. The following snippet of a task definition shows the required parameters:


"containerDefinitions": [
   {
      "image": "private-repo/private-image",
      "repositoryCredentials": {
         "credentialsParameter: "arn:aws:secretsmanager:region:aws_account_id:secret:secret_name"
      }
   }
]

For more information, see Private Registry Authentication for Tasks.

Clusters

Clusters can contain tasks using both the Fargate and EC2 launch types. When viewing your clusters in the AWS Management Console, Fargate and EC2 task counts are displayed separately.

For more information about Amazon ECS clusters, including a walkthrough for creating a cluster, see Amazon ECS Clusters.

Fargate Task Retirement

A Fargate task is scheduled to be retired when AWS detects the irreparable failure of the underlying hardware hosting the task or if a security issue needs to be patched. Most security patches are handled transparently without requiring any action on your part or having to restart your tasks. But for certain issues, we may require that the task be restarted.

When a task reaches its scheduled retirement date, it is stopped or terminated by AWS. If the task is part of a service, then the task is automatically stopped and the service scheduler starts a new one to replace it. If you are using standalone tasks, then you receive notification of the task retirement. For more information, see Task Retirement.

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