Request Syntax Request Parameters Response Syntax Response Elements Errors See Also

GetActivityTask

Used by workers to retrieve a task (with the specified activity ARN) which has been scheduled for execution by a running state machine. This initiates a long poll, where the service holds the HTTP connection open and responds as soon as a task becomes available (i.e. an execution of a task of this type is needed.) The maximum time the service holds on to the request before responding is 60 seconds. If no task is available within 60 seconds, the poll returns a taskToken with a null string.

Note

This API action isn't logged in CloudTrail.

Important

Workers should set their client side socket timeout to at least 65 seconds (5 seconds higher than the maximum time the service may hold the poll request).

Polling with GetActivityTask can cause latency in some implementations. See Avoid Latency When Polling for Activity Tasks in the Step Functions Developer Guide.

Request Syntax


{
   "activityArn": "string",
   "workerName": "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.

activityArn

The Amazon Resource Name (ARN) of the activity to retrieve tasks from (assigned when you create the task using CreateActivity.)

Type: String

Length Constraints: Minimum length of 1. Maximum length of 256.

Required: Yes

workerName

You can provide an arbitrary name in order to identify the worker that the task is assigned to. This name is used when it is logged in the execution history.

Type: String

Length Constraints: Minimum length of 1. Maximum length of 80.

Required: No

Response Syntax


{
   "input": "string",
   "taskToken": "string"
}

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.

input

The string that contains the JSON input data for the task. Length constraints apply to the payload size, and are expressed as bytes in UTF-8 encoding.

Type: String

Length Constraints: Maximum length of 262144.

taskToken

A token that identifies the scheduled task. This token must be copied and included in subsequent calls to SendTaskHeartbeat, SendTaskSuccess or SendTaskFailure in order to report the progress or completion of the task.

Type: String

Length Constraints: Minimum length of 1. Maximum length of 2048.

Errors

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

ActivityDoesNotExist

The specified activity does not exist.

HTTP Status Code: 400

ActivityWorkerLimitExceeded

The maximum number of workers concurrently polling for activity tasks has been reached.

HTTP Status Code: 400

InvalidArn

The provided Amazon Resource Name (ARN) is not valid.

HTTP Status Code: 400

KmsAccessDeniedException

Either your AWS KMS key policy or API caller does not have the required permissions.

HTTP Status Code: 400

KmsInvalidStateException

The AWS KMS key is not in valid state, for example: Disabled or Deleted.

HTTP Status Code: 400

KmsThrottlingException

Received when AWS KMS returns ThrottlingException for a AWS KMS call that Step Functions makes on behalf of the caller.

HTTP Status Code: 400