ShardHandler; why does it exist? Should it be used less?

[David Smiley <ds...@apache.org>]

Why does ShardHandler exist?  It lacks javadocs (as do most classes;
shame!) so I'm left to make guesses.  I'll make a straw-man claim here: a
SolrClient should be enough in most cases, maybe all cases with more work.
ShardHandler appears very async-centric (submit then call a different
method to collect a response).  Http2SolrClient in particular has an
asyncRequest method for that use-case.  By its name and my recollection of
its original and sole use (to search shards / distributed-search), I
believe this thing has been over-used for many other things in Solr for
Solr-to-Solr communication.

~ David Smiley
Apache Lucene/Solr Search Developer
http://www.linkedin.com/in/davidwsmiley