         @_all_hosts        = opts.all_hosts
         @_stats_cached     = undefined
         @_user_query_stats = new UserQueryStats(@dbg("user_query_stats"))
+        @_concurrent_queries = 0
 
         if opts.cache_expiry and opts.cache_size
             @_query_cache = (new require('expiring-lru-cache'))(size:opts.cache_size, expiry: opts.cache_expiry)

        # We monkey patch run to have similar semantics to rethinkdbdash, and nice logging and warnings.
        # See http://stackoverflow.com/questions/26287983/javascript-monkey-patch-the-rethinkdb-run
        # for how to monkey patch run.
        that = @ # needed to reconnect if connection dies
        TermBase = @r.expr(1).constructor.__super__.constructor.__super__
        run_cbs = {}
        if not TermBase.run_native?  # only do this once!

                            cb()  # so caller of this query gets an error.
                            return

                        that._concurrent_queries += 1

                        winston.debug("[#{that._concurrent_queries} concurrent]  rethink: query -- '#{query_string}'")
