but could you explain a little about how this works in with the existing basic auth stuff in HttpClientUtil
This was a hack introduced to add the basic auth headers when Solr makes inter-node requests. After 5.3 we have native support for inter-node authentication. This lets you to have only one user/pwd combination in the entire cluster which meant all requests were performed as same user
IMHO we should deprecate this.
This ticket makes the user/pwd configurable of a per request basis.
SolrRequest req ;req.setBasicAuthCredentials(userName, password);