
poll-for-task
*************


DESCRIPTION
===========

Task runners call this action 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 --worker-group parameter of the poll-for-task
call. The task returned by poll-for-task may come from any of the
pipelines that match the --worker-group 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, poll-for-task returns a response
immediately. If no tasks are available in the queue, poll-for-task
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 poll-for-
task again on the same --worker-group until it receives a response,
and this may take up to 90 seconds.


SYNOPSIS
========

   aws datapipeline poll-for-task
     --worker-group <value>
     [--hostname <value>]
     [--instance-identity <value>]


REQUIRED PARAMETERS
===================

"--worker-group"  (string)
   Indicates 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 --worker-group in the call to PollForTask. There are no
   wildcard values permitted in workerGroup, the string must be an
   exact, case-sensitive, match.


OPTIONAL PARAMETERS
===================

"--hostname"  (string)
   The public DNS name of the calling task runner.

"--instance-identity"  (structure)
   Identity information for the Amazon EC2 instance that is hosting
   the task runner. You can get this value by calling the URI,
   "http://169.254.169.254/latest/meta-data/instance-id" , from the
   EC2 instance. For more information, go to 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.

   "document"  (string)
      A description of an Amazon EC2 instance that is generated when
      the instance is launched and exposed to the instance via the
      instance meta-data service in the form of a JSON representation
      of an object.

   "signature"  (string)
      A signature which can be used to verify the accuracy and
      authenticity of the information provided in the instance
      identity document.

   *Parameter Syntax*

      {
        "document": "string",
        "signature": "string"
      }
