/*
HttpSolrServer is thread-safe and if you are using the following constructor,
you *MUST* re-use the same instance for all requests. If instances are created on
the fly, it can cause a connection leak. The recommended practice is to keep a
static instance of HttpSolrServer per solr server url and share it for all requests.
See https://issues.apache.org/jira/browse/SOLR-861 for more details
*/