You can publish your own metrics to CloudWatch with the put-metric-data command (or its Query API equivalent PutMetricData). When you create a new metric using the put-metric-data command, it can take up to two minutes before you can retrieve statistics on the new metric using the get-metric-statistics command.
However, it can take up to fifteen minutes before the new metric appears in the list of metrics retrieved using the list-metrics command.
http://docs.aws.amazon.com/AmazonCloudWatch/latest/DeveloperGuide/publishingMetrics.html

Explanation/Reference:
Explanation:
Task runners call PollForTask to receive a task to perform from AWS Data Pipeline. 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 90 seconds, during which time any newly scheduled tasks are handed to the task agent. Your remote worker should not call PollForTask again on the same worker group until it receives a response, and this may take up to 90 seconds.
http://docs.aws.amazon.com/datapipeline/latest/APIReference/API_PollForTask.html