Service Definition Parameters

A service definition defines which task definition to use with your service, how many instantiations of that task to run, and which load balancers (if any) to associate with your tasks.


{
    "cluster": "",
    "serviceName": "",
    "taskDefinition": "",
    "loadBalancers": [
        {
            "targetGroupArn": "",
            "loadBalancerName": "",
            "containerName": "",
            "containerPort": 0
        }
    ],
    "serviceRegistries": [
        {
            "registryArn": "",
            "port": 0,
            "containerName": "",
            "containerPort": 0
        }
    ],
    "desiredCount": 0,
    "clientToken": "",
    "launchType": "EC2",
    "platformVersion": "",
    "role": "",
    "deploymentConfiguration": {
        "maximumPercent": 0,
        "minimumHealthyPercent": 0
    },
    "placementConstraints": [
        {
            "type": "memberOf",
            "expression": ""
        }
    ],
    "placementStrategy": [
        {
            "type": "random",
            "field": ""
        }
    ],
    "networkConfiguration": {
        "awsvpcConfiguration": {
            "subnets": [
                ""
            ],
            "securityGroups": [
                ""
            ],
            "assignPublicIp": "ENABLED"
        }
    },
    "healthCheckGracePeriodSeconds": 0,
    "schedulingStrategy": "REPLICA"
}

Note

You can create the above service definition template with the following AWS CLI command.


aws ecs create-service --generate-cli-skeleton

You can specify the following parameters in a service definition.

cluster

The short name or full Amazon Resource Name (ARN) of the cluster on which to run your service. If you do not specify a cluster, the default cluster is assumed.

serviceName

The name of your service. Up to 255 letters (uppercase and lowercase), numbers, hyphens, and underscores are allowed. Service names must be unique within a cluster, but you can have similarly named services in multiple clusters within a region or across multiple regions.

taskDefinition

The family and revision (family:revision) or full ARN of the task definition to run in your service. If a revision is not specified, the latest ACTIVE revision is used.

loadBalancers

A load balancer object representing the load balancer to use with your service. Currently, you are limited to one load balancer or target group per service. After you create a service, the load balancer name or target group ARN, container name, and container port specified in the service definition are immutable.

For Classic Load Balancers, this object must contain the load balancer name, the container name (as it appears in a container definition), and the container port to access from the load balancer. When a task from this service is placed on a container instance, the container instance is registered with the load balancer specified here.

For Application Load Balancers and Network Load Balancers, this object must contain the load balancer target group ARN, the container name (as it appears in a container definition), and the container port to access from the load balancer. When a task from this service is placed on a container instance, the container instance and port combination is registered as a target in the target group specified here.

targetGroupArn: The full Amazon Resource Name (ARN) of the Elastic Load Balancing target group associated with a service.
loadBalancerName: The name of the load balancer.
containerName: The name of the container (as it appears in a container definition) to associate with the load balancer.
containerPort: The port on the container to associate with the load balancer. This port must correspond to a containerPort in the service's task definition. Your container instances must allow ingress traffic on the hostPort of the port mapping.

serviceRegistries

The details of the service discovery configuration for your service. For more information, see Service Discovery.

registryArn: The Amazon Resource Name (ARN) of the service registry. The currently supported service registry is Amazon Route 53 Auto Naming. For more information, see Service.
port: The port value used if your service discovery service specified an SRV record. This field is required if both the awsvpc network mode and SRV records are used.
containerName: The container name value, already specified in the task definition, to be used for your service discovery service. If the task definition that your service task specifies uses the bridge or host network mode, you must specify a containerName and containerPort combination from the task definition. If the task definition that your service task specifies uses the code network mode and a type SRV DNS record is used, you must specify either a containerName and containerPort combination or a port value, but not both.
containerPort: The port value, already specified in the task definition, to be used for your service discovery service. If the task definition your service task specifies uses the bridge or host network mode, you must specify a containerName and containerPort combination from the task definition. If the task definition your service task specifies uses the awsvpc network mode and a type SRV DNS record is used, you must specify either a containerName and containerPort combination or a port value, but not both.

desiredCount

The number of instantiations of the specified task definition to place and keep running on your cluster.

clientToken

Unique, case-sensitive identifier you provide to ensure the idempotency of the request. Up to 32 ASCII characters are allowed.

launchType

The launch type on which to run your service. If one is not specified, EC2 is used by default. For more information, see Amazon ECS Launch Types.

platformVersion

The platform version on which to run your service. If one is not specified, the latest version (LATEST) is used by default.

AWS Fargate platform versions are used to refer to a specific runtime environment for the Fargate task infrastructure. When specifying the LATEST platform version when running a task or creating a service, you get the most current platform version available for your tasks. When you scale up your service, those tasks receive the platform version that was specified on the service's current deployment. For more information, see AWS Fargate Platform Versions.

Note

Platform versions are not specified for tasks using the EC2 launch type.

role

The name or full Amazon Resource Name (ARN) of the IAM role that allows Amazon ECS to make calls to your load balancer on your behalf. This parameter is required if you are using a load balancer with your service. If you specify the role parameter, you must also specify a load balancer object with the loadBalancers parameter.

If your specified role has a path other than /, then you must either specify the full role ARN (this is recommended) or prefix the role name with the path. For example, if a role with the name bar has a path of /foo/ then you would specify /foo/bar as the role name. For more information, see Friendly Names and Paths in the IAM User Guide.

deploymentConfiguration

Optional deployment parameters that control how many tasks run during the deployment and the ordering of stopping and starting tasks.

maximumPercent

The maximumPercent parameter represents an upper limit on the number of your service's tasks that are allowed in the RUNNING or PENDING state during a deployment, as a percentage of the desiredCount (rounded down to the nearest integer). This parameter enables you to define the deployment batch size. For example, if your replica service has a desiredCount of four tasks and a maximumPercent value of 200%, the scheduler may start four new tasks before stopping the four older tasks (provided that the cluster resources required to do this are available). The default value for a replica service for maximumPercent is 200%.

If you are using a daemon service type, the maximumPercent should remain at 100%, which is the default value.

The maximum number of tasks during a deployment is the desiredCount multiplied by the maximumPercent/100, rounded down to the nearest integer value.

minimumHealthyPercent

The minimumHealthyPercent represents a lower limit on the number of your service's tasks that must remain in the RUNNING state during a deployment, as a percentage of the desiredCount (rounded up to the nearest integer). This parameter enables you to deploy without using additional cluster capacity. For example, if your service has a desiredCount of four tasks and a minimumHealthyPercent of 50%, the scheduler may stop two existing tasks to free up cluster capacity before starting two new tasks. Tasks for services that do not use a load balancer are considered healthy if they are in the RUNNING state. Tasks for services that do use a load balancer are considered healthy if they are in the RUNNING state and the container instance on which the load balancer is hosted is reported as healthy. The default value for a replica service for minimumHealthyPercent is 50% in the AWS Management Console and 100% for the AWS CLI, the AWS SDKs, and the APIs. The default value for a daemon service for minimumHealthyPercent is 0% for the AWS CLI, the AWS SDKs, and the APIs and 50% for the AWS Management Console.

The minimum number of healthy tasks during a deployment is the desiredCount multiplied by the minimumHealthyPercent/100, rounded up to the nearest integer value.

placementConstraints

An array of placement constraint objects to use for tasks in your service. You can specify a maximum of 10 constraints per task (this limit includes constraints in the task definition and those specified at run time). If you are using the Fargate launch type, task placement constraints are not supported.

type: The type of constraint. Use distinctInstance to ensure that each task in a particular group is running on a different container instance. Use memberOf to restrict the selection to a group of valid candidates. The value distinctInstance is not supported in task definitions.
expression: A cluster query language expression to apply to the constraint. Note you cannot specify an expression if the constraint type is distinctInstance. For more information, see Cluster Query Language.

placementStrategy

The placement strategy objects to use for tasks in your service. You can specify a maximum of four strategy rules per service.

type: The type of placement strategy. The random placement strategy randomly places tasks on available candidates. The spread placement strategy spreads placement across available candidates evenly based on the field parameter. The binpack strategy places tasks on available candidates that have the least available amount of the resource that is specified with the field parameter. For example, if you binpack on memory, a task is placed on the instance with the least amount of remaining memory (but still enough to run the task).
field: The field to apply the placement strategy against. For the spread placement strategy, valid values are instanceId (or host, which has the same effect), or any platform or custom attribute that is applied to a container instance, such as attribute:ecs.availability-zone. For the binpack placement strategy, valid values are cpu and memory. For the random placement strategy, this field is not used.

networkConfiguration

The network configuration for the service. This parameter is required for task definitions that use the awsvpc network mode to receive their own Elastic Network Interface, and it is not supported for other network modes. If using the Fargate launch type, the awsvpc network mode is required. For more information, see Task Networking with the awsvpc Network Mode.

awsvpcConfiguration

An object representing the subnets and security groups for a task or service.

subnets: The subnets associated with the task or service.
securityGroups: The security groups associated with the task or service. If you do not specify a security group, the default security group for the VPC is used.
assignPublicIP: Whether the task's elastic network interface receives a public IP address.

healthCheckGracePeriodSeconds

The period of time, in seconds, that the Amazon ECS service scheduler should ignore unhealthy Elastic Load Balancing target health checks after a task has first started. This is only valid if your service is configured to use a load balancer. If your service's tasks take a while to start and respond to health checks, you can specify a health check grace period of up to 7,200 seconds during which the ECS service scheduler ignores the health check status. This grace period can prevent the ECS service scheduler from marking tasks as unhealthy and stopping them before they have time to come up.

schedulingStrategy

The scheduling strategy to use. For more information, see Service Scheduler Concepts.

There are two service scheduler strategies available:

REPLICA—The replica scheduling strategy places and maintains the desired number of tasks across your cluster. By default, the service scheduler spreads tasks across Availability Zones. You can use task placement strategies and constraints to customize task placement decisions. For more information, see Replica.
DAEMON—The daemon scheduling strategy deploys exactly one task on each active container instance that meets all of the task placement constraints that you specify in your cluster. When using this strategy, there is no need to specify a desired number of tasks, a task placement strategy, or use Service Auto Scaling policies. For more information, see Daemon.

Note

Fargate tasks do not support the DAEMON scheduling strategy.

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