RunTask - Amazon Elastic Container Service
Services or capabilities described in Amazon Web Services documentation might vary by Region. To see the differences applicable to the China Regions, see Getting Started with Amazon Web Services in China (PDF).


Starts a new task using the specified task definition.


On March 21, 2024, a change was made to resolve the task definition revision before authorization. When a task definition revision is not specified, authorization will occur using the latest revision of a task definition.

You can allow Amazon ECS to place tasks for you, or you can customize how Amazon ECS places tasks using placement constraints and placement strategies. For more information, see Scheduling Tasks in the Amazon Elastic Container Service Developer Guide.

Alternatively, you can use StartTask to use your own scheduler or place tasks manually on specific container instances.

Starting April 15, 2023, Amazon will not onboard new customers to Amazon Elastic Inference (EI), and will help current customers migrate their workloads to options that offer better price and performance. After April 15, 2023, new customers will not be able to launch instances with Amazon EI accelerators in Amazon SageMaker, Amazon ECS, or Amazon EC2. However, customers who have used Amazon EI at least once during the past 30-day period are considered current customers and will be able to continue using the service.

You can attach Amazon EBS volumes to Amazon ECS tasks by configuring the volume when creating or updating a service. For more infomation, see Amazon EBS volumes in the Amazon Elastic Container Service Developer Guide.

The Amazon ECS API follows an eventual consistency model. This is because of the distributed nature of the system supporting the API. This means that the result of an API command you run that affects your Amazon ECS resources might not be immediately visible to all subsequent commands you run. Keep this in mind when you carry out an API command that immediately follows a previous API command.

To manage eventual consistency, you can do the following:

  • Confirm the state of the resource before you run a command to modify it. Run the DescribeTasks command using an exponential backoff algorithm to ensure that you allow enough time for the previous command to propagate through the system. To do this, run the DescribeTasks command repeatedly, starting with a couple of seconds of wait time and increasing gradually up to five minutes of wait time.

  • Add wait time between subsequent commands, even if the DescribeTasks command returns an accurate response. Apply an exponential backoff algorithm starting with a couple of seconds of wait time, and increase gradually up to about five minutes of wait time.

Request Syntax

{ "capacityProviderStrategy": [ { "base": number, "capacityProvider": "string", "weight": number } ], "clientToken": "string", "cluster": "string", "count": number, "enableECSManagedTags": boolean, "enableExecuteCommand": boolean, "group": "string", "launchType": "string", "networkConfiguration": { "awsvpcConfiguration": { "assignPublicIp": "string", "securityGroups": [ "string" ], "subnets": [ "string" ] } }, "overrides": { "containerOverrides": [ { "command": [ "string" ], "cpu": number, "environment": [ { "name": "string", "value": "string" } ], "environmentFiles": [ { "type": "string", "value": "string" } ], "memory": number, "memoryReservation": number, "name": "string", "resourceRequirements": [ { "type": "string", "value": "string" } ] } ], "cpu": "string", "ephemeralStorage": { "sizeInGiB": number }, "executionRoleArn": "string", "inferenceAcceleratorOverrides": [ { "deviceName": "string", "deviceType": "string" } ], "memory": "string", "taskRoleArn": "string" }, "placementConstraints": [ { "expression": "string", "type": "string" } ], "placementStrategy": [ { "field": "string", "type": "string" } ], "platformVersion": "string", "propagateTags": "string", "referenceId": "string", "startedBy": "string", "tags": [ { "key": "string", "value": "string" } ], "taskDefinition": "string", "volumeConfigurations": [ { "managedEBSVolume": { "encrypted": boolean, "filesystemType": "string", "iops": number, "kmsKeyId": "string", "roleArn": "string", "sizeInGiB": number, "snapshotId": "string", "tagSpecifications": [ { "propagateTags": "string", "resourceType": "string", "tags": [ { "key": "string", "value": "string" } ] } ], "terminationPolicy": { "deleteOnTermination": boolean }, "throughput": number, "volumeType": "string" }, "name": "string" } ] }

Request Parameters

For information about the parameters that are common to all actions, see Common Parameters.

The request accepts the following data in JSON format.


The capacity provider strategy to use for the task.

If a capacityProviderStrategy is specified, the launchType parameter must be omitted. If no capacityProviderStrategy or launchType is specified, the defaultCapacityProviderStrategy for the cluster is used.

When you use cluster auto scaling, you must specify capacityProviderStrategy and not launchType.

A capacity provider strategy may contain a maximum of 6 capacity providers.

Type: Array of CapacityProviderStrategyItem objects

Required: No


An identifier that you provide to ensure the idempotency of the request. It must be unique and is case sensitive. Up to 64 characters are allowed. The valid characters are characters in the range of 33-126, inclusive. For more information, see Ensuring idempotency.

Type: String

Required: No


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

Type: String

Required: No


The number of instantiations of the specified task to place on your cluster. You can specify up to 10 tasks for each call.

Type: Integer

Required: No


Specifies whether to use Amazon ECS managed tags for the task. For more information, see Tagging Your Amazon ECS Resources in the Amazon Elastic Container Service Developer Guide.

Type: Boolean

Required: No


Determines whether to use the execute command functionality for the containers in this task. If true, this enables execute command functionality on all containers in the task.

If true, then the task definition must have a task role, or you must provide one as an override.

Type: Boolean

Required: No


The name of the task group to associate with the task. The default value is the family name of the task definition (for example, family:my-family-name).

Type: String

Required: No


The infrastructure to run your standalone task on. For more information, see Amazon ECS launch types in the Amazon Elastic Container Service Developer Guide.

The FARGATE launch type runs your tasks on Amazon Fargate On-Demand infrastructure.


Fargate Spot infrastructure is available for use but a capacity provider strategy must be used. For more information, see Amazon Fargate capacity providers in the Amazon ECS Developer Guide.

The EC2 launch type runs your tasks on Amazon EC2 instances registered to your cluster.

The EXTERNAL launch type runs your tasks on your on-premises server or virtual machine (VM) capacity registered to your cluster.

A task can use either a launch type or a capacity provider strategy. If a launchType is specified, the capacityProviderStrategy parameter must be omitted.

When you use cluster auto scaling, you must specify capacityProviderStrategy and not launchType.

Type: String

Valid Values: EC2 | FARGATE | EXTERNAL

Required: No


The network configuration for the task. This parameter is required for task definitions that use the awsvpc network mode to receive their own elastic network interface, and it isn't supported for other network modes. For more information, see Task networking in the Amazon Elastic Container Service Developer Guide.

Type: NetworkConfiguration object

Required: No


A list of container overrides in JSON format that specify the name of a container in the specified task definition and the overrides it should receive. You can override the default command for a container (that's specified in the task definition or Docker image) with a command override. You can also override existing environment variables (that are specified in the task definition or Docker image) on a container or add new environment variables to it with an environment override.

A total of 8192 characters are allowed for overrides. This limit includes the JSON formatting characters of the override structure.

Type: TaskOverride object

Required: No


An array of placement constraint objects to use for the task. You can specify up to 10 constraints for each task (including constraints in the task definition and those specified at runtime).

Type: Array of PlacementConstraint objects

Required: No


The placement strategy objects to use for the task. You can specify a maximum of 5 strategy rules for each task.

Type: Array of PlacementStrategy objects

Required: No


The platform version the task uses. A platform version is only specified for tasks hosted on Fargate. If one isn't specified, the LATEST platform version is used. For more information, see Amazon Fargate platform versions in the Amazon Elastic Container Service Developer Guide.

Type: String

Required: No


Specifies whether to propagate the tags from the task definition to the task. If no value is specified, the tags aren't propagated. Tags can only be propagated to the task during task creation. To add tags to a task after task creation, use the TagResource API action.


An error will be received if you specify the SERVICE option when running a task.

Type: String


Required: No


The reference ID to use for the task. The reference ID can have a maximum length of 1024 characters.

Type: String

Required: No


An optional tag specified when a task is started. For example, if you automatically trigger a task to run a batch process job, you could apply a unique identifier for that job to your task with the startedBy parameter. You can then identify which tasks belong to that job by filtering the results of a ListTasks call with the startedBy value. Up to 128 letters (uppercase and lowercase), numbers, hyphens (-), and underscores (_) are allowed.

If a task is started by an Amazon ECS service, then the startedBy parameter contains the deployment ID of the service that starts it.

Type: String

Required: No


The metadata that you apply to the task to help you categorize and organize them. Each tag consists of a key and an optional value, both of which you define.

The following basic restrictions apply to tags:

  • Maximum number of tags per resource - 50

  • For each resource, each tag key must be unique, and each tag key can have only one value.

  • Maximum key length - 128 Unicode characters in UTF-8

  • Maximum value length - 256 Unicode characters in UTF-8

  • If your tagging schema is used across multiple services and resources, remember that other services may have restrictions on allowed characters. Generally allowed characters are: letters, numbers, and spaces representable in UTF-8, and the following characters: + - = . _ : / @.

  • Tag keys and values are case-sensitive.

  • Do not use aws:, AWS:, or any upper or lowercase combination of such as a prefix for either keys or values as it is reserved for Amazon use. You cannot edit or delete tag keys or values with this prefix. Tags with this prefix do not count against your tags per resource limit.

Type: Array of Tag objects

Array Members: Minimum number of 0 items. Maximum number of 50 items.

Required: No


The family and revision (family:revision) or full ARN of the task definition to run. If a revision isn't specified, the latest ACTIVE revision is used.

The full ARN value must match the value that you specified as the Resource of the principal's permissions policy.

When you specify a task definition, you must either specify a specific revision, or all revisions in the ARN.

To specify a specific revision, include the revision number in the ARN. For example, to specify revision 2, use arn:aws:ecs:us-east-1:111122223333:task-definition/TaskFamilyName:2.

To specify all revisions, use the wildcard (*) in the ARN. For example, to specify all revisions, use arn:aws:ecs:us-east-1:111122223333:task-definition/TaskFamilyName:*.

For more information, see Policy Resources for Amazon ECS in the Amazon Elastic Container Service Developer Guide.

Type: String

Required: Yes


The details of the volume that was configuredAtLaunch. You can configure the size, volumeType, IOPS, throughput, snapshot and encryption in in TaskManagedEBSVolumeConfiguration. The name of the volume must match the name from the task definition.

Type: Array of TaskVolumeConfiguration objects

Required: No

Response Syntax

{ "failures": [ { "arn": "string", "detail": "string", "reason": "string" } ], "tasks": [ { "attachments": [ { "details": [ { "name": "string", "value": "string" } ], "id": "string", "status": "string", "type": "string" } ], "attributes": [ { "name": "string", "targetId": "string", "targetType": "string", "value": "string" } ], "availabilityZone": "string", "capacityProviderName": "string", "clusterArn": "string", "connectivity": "string", "connectivityAt": number, "containerInstanceArn": "string", "containers": [ { "containerArn": "string", "cpu": "string", "exitCode": number, "gpuIds": [ "string" ], "healthStatus": "string", "image": "string", "imageDigest": "string", "lastStatus": "string", "managedAgents": [ { "lastStartedAt": number, "lastStatus": "string", "name": "string", "reason": "string" } ], "memory": "string", "memoryReservation": "string", "name": "string", "networkBindings": [ { "bindIP": "string", "containerPort": number, "containerPortRange": "string", "hostPort": number, "hostPortRange": "string", "protocol": "string" } ], "networkInterfaces": [ { "attachmentId": "string", "ipv6Address": "string", "privateIpv4Address": "string" } ], "reason": "string", "runtimeId": "string", "taskArn": "string" } ], "cpu": "string", "createdAt": number, "desiredStatus": "string", "enableExecuteCommand": boolean, "ephemeralStorage": { "sizeInGiB": number }, "executionStoppedAt": number, "fargateEphemeralStorage": { "kmsKeyId": "string", "sizeInGiB": number }, "group": "string", "healthStatus": "string", "inferenceAccelerators": [ { "deviceName": "string", "deviceType": "string" } ], "lastStatus": "string", "launchType": "string", "memory": "string", "overrides": { "containerOverrides": [ { "command": [ "string" ], "cpu": number, "environment": [ { "name": "string", "value": "string" } ], "environmentFiles": [ { "type": "string", "value": "string" } ], "memory": number, "memoryReservation": number, "name": "string", "resourceRequirements": [ { "type": "string", "value": "string" } ] } ], "cpu": "string", "ephemeralStorage": { "sizeInGiB": number }, "executionRoleArn": "string", "inferenceAcceleratorOverrides": [ { "deviceName": "string", "deviceType": "string" } ], "memory": "string", "taskRoleArn": "string" }, "platformFamily": "string", "platformVersion": "string", "pullStartedAt": number, "pullStoppedAt": number, "startedAt": number, "startedBy": "string", "stopCode": "string", "stoppedAt": number, "stoppedReason": "string", "stoppingAt": number, "tags": [ { "key": "string", "value": "string" } ], "taskArn": "string", "taskDefinitionArn": "string", "version": number } ] }

Response Elements

If the action is successful, the service sends back an HTTP 200 response.

The following data is returned in JSON format by the service.


Any failures associated with the call.

For information about how to address failures, see Service event messages and API failure reasons in the Amazon Elastic Container Service Developer Guide.

Type: Array of Failure objects


A full description of the tasks that were run. The tasks that were successfully placed on your cluster are described here.

Type: Array of Task objects


For information about the errors that are common to all actions, see Common Errors.


You don't have authorization to perform the requested action.

HTTP Status Code: 400


Your Amazon account was blocked. For more information, contact Amazon Web Services Support.

HTTP Status Code: 400


These errors are usually caused by a client action. This client action might be using an action or resource on behalf of a user that doesn't have permissions to use the action or resource. Or, it might be specifying an identifier that isn't valid.

The following list includes additional causes for the error:

  • The RunTask could not be processed because you use managed scaling and there is a capacity error because the quota of tasks in the PROVISIONING per cluster has been reached. For information about the service quotas, see Amazon ECS service quotas.

HTTP Status Code: 400


The specified cluster wasn't found. You can view your available clusters with ListClusters. Amazon ECS clusters are Region specific.

HTTP Status Code: 400


The RunTask request could not be processed due to conflicts. The provided clientToken is already in use with a different RunTask request. The resourceIds are the existing task ARNs which are already associated with the clientToken.

To fix this issue:

  • Run RunTask with a unique clientToken.

  • Run RunTask with the clientToken and the original set of parameters

HTTP Status Code: 400


The specified parameter isn't valid. Review the available parameters for the API request.

HTTP Status Code: 400


The specified platform version doesn't satisfy the required capabilities of the task definition.

HTTP Status Code: 400


The specified platform version doesn't exist.

HTTP Status Code: 400


These errors are usually caused by a server issue.

HTTP Status Code: 500


The specified task isn't supported in this Region.

HTTP Status Code: 400


In the following example or examples, the Authorization header contents (AUTHPARAMS) must be replaced with an Amazon Signature Version 4 signature. For more information, see Signature Version 4 Signing Process in the Amazon General Reference.

You only need to learn how to sign HTTP requests if you intend to create them manually. When you use the Amazon Command Line Interface or one of the Amazon SDKs to make requests to Amazon, these tools automatically sign the requests for you, with the access key that you specify when you configure the tools. When you use these tools, you don't have to sign requests yourself.


This example request runs the latest ACTIVE revision of the hello_world task definition family in the default cluster.

Sample Request

POST / HTTP/1.1 Host: Accept-Encoding: identity Content-Length: 45 X-Amz-Target: AmazonEC2ContainerServiceV20141113.RunTask X-Amz-Date: 20161121T215740Z User-Agent: aws-cli/1.11.13 Python/2.7.12 Darwin/16.1.0 botocore/1.4.66 Content-Type: application/x-amz-json-1.1 Authorization: AUTHPARAMS { "count": 1, "taskDefinition": "hello_world", ""clientToken": "550e8400-e29b-41d4-a716-446655440000" }

Sample Response

HTTP/1.1 200 OK Server: Server Date: Mon, 21 Nov 2016 21:57:40 GMT Content-Type: application/x-amz-json-1.1 Content-Length: 1025 Connection: keep-alive x-amzn-RequestId: 123a4b56-7c89-01d2-3ef4-example5678f { "failures": [], "tasks": [ { "clusterArn": "arn:aws:ecs:us-east-1:012345678910:cluster/default", "containerInstanceArn": "arn:aws:ecs:us-east-1:012345678910:container-instance/default/4c543eed-f83f-47da-b1d8-3d23f1da4c64", "containers": [ { "containerArn": "arn:aws:ecs:us-east-1:012345678910:container/default/e76594d4-27e1-4c74-98b5-46a6435eb769", "lastStatus": "PENDING", "name": "wordpress", "taskArn": "arn:aws:ecs:us-east-1:012345678910:task/default/fdf2c302-468c-4e55-b884-5331d816e7fb" }, { "containerArn": "arn:aws:ecs:us-east-1:012345678910:container/b19106ea-4fa8-4f1d-9767-96922c82b070", "lastStatus": "PENDING", "name": "mysql", "taskArn": "arn:aws:ecs:us-east-1:012345678910:task/default/fdf2c302-468c-4e55-b884-5331d816e7fb" } ], "createdAt": 1479765460.842, "desiredStatus": "RUNNING", "lastStatus": "PENDING", "overrides": { "containerOverrides": [ { "name": "wordpress" }, { "name": "mysql" } ] }, "taskArn": "arn:aws:ecs:us-east-1:012345678910:task/default/fdf2c302-468c-4e55-b884-5331d816e7fb", "taskDefinitionArn": "arn:aws:ecs:us-east-1:012345678910:task-definition/hello_world:6", "version": 1 } ] }

See Also

For more information about using this API in one of the language-specific Amazon SDKs, see the following: