pollForTask method

Future<PollForTaskOutput> pollForTask({ required String workerGroup, String? hostname, InstanceIdentity? instanceIdentity, })

Task runners call PollForTask to receive a task to perform from AWS Data Pipeline. The task runner specifies which tasks it can perform by setting a value for the workerGroup parameter. The task returned can come from any of the pipelines that match the workerGroup value passed in by the task runner and that was launched using the IAM user credentials specified by the task runner.

If tasks are ready in the work queue, PollForTask returns a response immediately. If no tasks are available in the queue, PollForTask uses long-polling and holds on to a poll connection for up to a 90 seconds, during which time the first newly scheduled task is handed to the task runner. To accomodate this, set the socket timeout in your task runner to 90 seconds. The task runner should not call PollForTask again on the same workerGroup until it receives a response, and this can take up to 90 seconds.

May throw InternalServiceError. May throw InvalidRequestException. May throw TaskNotFoundException.

Parameter workerGroup : The type of task the task runner is configured to accept and process. The worker group is set as a field on objects in the pipeline when they are created. You can only specify a single value for workerGroup in the call to PollForTask. There are no wildcard values permitted in workerGroup; the string must be an exact, case-sensitive, match.

Parameter hostname : The public DNS name of the calling task runner.

Parameter instanceIdentity : Identity information for the EC2 instance that is hosting the task runner. You can get this value from the instance using http://169.254.169.254/latest/meta-data/instance-id. For more information, see Instance Metadata in the Amazon Elastic Compute Cloud User Guide. Passing in this value proves that your task runner is running on an EC2 instance, and ensures the proper AWS Data Pipeline service charges are applied to your pipeline.

Implementation

Future<PollForTaskOutput> pollForTask({
  required String workerGroup,
  String? hostname,
  InstanceIdentity? instanceIdentity,
}) async {
  ArgumentError.checkNotNull(workerGroup, 'workerGroup');
  _s.validateStringLength(
    'workerGroup',
    workerGroup,
    0,
    1024,
    isRequired: true,
  );
  _s.validateStringLength(
    'hostname',
    hostname,
    1,
    1024,
  );
  final headers = <String, String>{
    'Content-Type': 'application/x-amz-json-1.1',
    'X-Amz-Target': 'DataPipeline.PollForTask'
  };
  final jsonResponse = await _protocol.send(
    method: 'POST',
    requestUri: '/',
    exceptionFnMap: _exceptionFns,
    // TODO queryParams
    headers: headers,
    payload: {
      'workerGroup': workerGroup,
      if (hostname != null) 'hostname': hostname,
      if (instanceIdentity != null) 'instanceIdentity': instanceIdentity,
    },
  );

  return PollForTaskOutput.fromJson(jsonResponse.body);
}