a function that returns the collection name and a testQuery for the given server. The collection is used to partition server when classifying "fast"/"slow" servers, because for different collections response times will be different. It's somehow similar with the testQuery: it might be different per server, e.g. some server might only provide a /suggest handler while others provide /select (which can be specified via the "qt" query param in the test query).
solrServers
solr servers to load balance, those are regularly tested.