I'm not sure what is the correct property to get the number of docs with the new metrics API in Solr
Going to the URL directly will give you all available metrics. If you search this list for doc
, one of the first hits will be:
"SEARCHER.searcher.maxDoc":3,
"SEARCHER.searcher.numDocs":3,
These are located under the metrics/solr.core.<core_name>
element.