If you want to explore how to parallelize the data ingestion into Elasticsearch, please have a look to this post I have written for Amazon AWS:

http://blogs.aws.amazon.com/bigdata/post/TxC0CXZ3RPPK7O/Indexing-Common-Crawl-Metadata-on-Amazon-EMR-Using-Cascading-and-Elasticsearch

It explains how to index Common Crawl metadata into Elasticsearch using Cascading connector directly from the S3 data source.

Cascading Source Code is available here.