pollForActivityTask method

Future<ActivityTask> pollForActivityTask({ required String domain, required TaskList taskList, String? identity, })

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. 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.

May throw UnknownResourceFault. May throw OperationNotPermittedFault. May throw LimitExceededFault.

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

Parameter taskList : 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.

Parameter identity : 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.

Implementation

Future<ActivityTask> pollForActivityTask({
  required String domain,
  required TaskList taskList,
  String? identity,
}) async {
  ArgumentError.checkNotNull(domain, 'domain');
  _s.validateStringLength(
    'domain',
    domain,
    1,
    256,
    isRequired: true,
  );
  ArgumentError.checkNotNull(taskList, 'taskList');
  _s.validateStringLength(
    'identity',
    identity,
    0,
    256,
  );
  final headers = <String, String>{
    'Content-Type': 'application/x-amz-json-1.0',
    'X-Amz-Target': 'SimpleWorkflowService.PollForActivityTask'
  };
  final jsonResponse = await _protocol.send(
    method: 'POST',
    requestUri: '/',
    exceptionFnMap: _exceptionFns,
    // TODO queryParams
    headers: headers,
    payload: {
      'domain': domain,
      'taskList': taskList,
      if (identity != null) 'identity': identity,
    },
  );

  return ActivityTask.fromJson(jsonResponse.body);
}