PollForActivityTaskCommand

Suggest an Edit

Used by workers to get an ActivityTask from the specified activity taskList. This initiates a long poll, where the service holds the HTTP connection open and responds as soon as a task becomes available. 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 an empty result. An empty result, in this context, means that an ActivityTask is returned, but that the value of taskToken is an empty string. If a task is returned, the worker should use its type to identify and process it correctly.

Workers should set their client side socket timeout to at least 70 seconds (10 seconds higher than the maximum time service may hold the poll request).

Access Control

You can use IAM policies to control this action's access to Amazon SWF resources as follows:

  • Use a Resource element with the domain name to limit the action to only specified domains.

  • Use an Action element to allow or deny permission to call this action.

  • Constrain the taskList.name parameter by using a Condition element with the swf:taskList.name key to allow the action to access only certain task lists.

If the caller doesn't have sufficient permissions to invoke the action, or the parameter values fall outside the specified constraints, the action fails. The associated event attribute's cause parameter is set to OPERATION_NOT_PERMITTED. For details and example IAM policies, see Using IAM to Manage Access to Amazon SWF Workflows  in the Amazon SWF Developer Guide.

Example Syntax

Use a bare-bones client and the command you need to make an API call.

import { SWFClient, PollForActivityTaskCommand } from "@aws-sdk/client-swf"; // ES Modules import
// const { SWFClient, PollForActivityTaskCommand } = require("@aws-sdk/client-swf"); // CommonJS import
const client = new SWFClient(config);
const input = { // PollForActivityTaskInput
  domain: "STRING_VALUE", // required
  taskList: { // TaskList
    name: "STRING_VALUE", // required
  },
  identity: "STRING_VALUE",
};
const command = new PollForActivityTaskCommand(input);
const response = await client.send(command);
// { // ActivityTask
//   taskToken: "STRING_VALUE", // required
//   activityId: "STRING_VALUE", // required
//   startedEventId: Number("long"), // required
//   workflowExecution: { // WorkflowExecution
//     workflowId: "STRING_VALUE", // required
//     runId: "STRING_VALUE", // required
//   },
//   activityType: { // ActivityType
//     name: "STRING_VALUE", // required
//     version: "STRING_VALUE", // required
//   },
//   input: "STRING_VALUE",
// };

PollForActivityTaskCommand Input

See PollForActivityTaskCommandInput for more details

Parameter
Type
Description
domain
Required
string | undefined

The name of the domain that contains the task lists being polled.

taskList
Required
TaskList | undefined

Specifies the task list to poll for activity tasks.

The specified string must not start or end with whitespace. It must not contain a : (colon), / (slash), | (vertical bar), or any control characters (u0000-u001f | u007f-u009f). Also, it must not be the literal string arn.

identity
string | undefined

Identity of the worker making the request, recorded in the ActivityTaskStarted event in the workflow history. This enables diagnostic tracing when problems arise. The form of this identity is user defined.

PollForActivityTaskCommand Output

See PollForActivityTaskCommandOutput for details

Parameter
Type
Description
$metadata
Required
ResponseMetadata
Metadata pertaining to this request.
activityId
Required
string | undefined

The unique ID of the task.

activityType
Required
ActivityType | undefined

The type of this activity task.

startedEventId
Required
number | undefined

The ID of the ActivityTaskStarted event recorded in the history.

taskToken
Required
string | undefined

The opaque string used as a handle on the task. This token is used by workers to communicate progress and response information back to the system about the task.

workflowExecution
Required
WorkflowExecution | undefined

The workflow execution that started this activity task.

input
string | undefined

The inputs provided when the activity task was scheduled. The form of the input is user defined and should be meaningful to the activity implementation.

Throws

Name
Fault
Details
LimitExceededFault
client

Returned by any operation if a system imposed limitation has been reached. To address this fault you should either clean up unused resources or increase the limit by contacting AWS.

OperationNotPermittedFault
client

Returned when the caller doesn't have sufficient permissions to invoke the action.

UnknownResourceFault
client

Returned when the named resource cannot be found with in the scope of this operation (region or domain). This could happen if the named resource was never created or is no longer available for this operation.

SWFServiceException
Base exception class for all service exceptions from SWF service.