Running 4.2.4, these errors show up every once and a while when doing a search on a search head:
"Reached end-of-stream while waiting for more data from peer
<indexer>. Search results might be incomplete!"
"[<indexer>] Streamed search execute failed because: Attempted to
get current default indexes when no context was set"
<indexer> will be any one of our indexers.
Retrying the search works.
This has been answered here: http://splunk-base.splunk.com/answers/83394/reached-end-of-stream-error-troubleshooting