                         that._concurrent_queries ?= 0
                         that._concurrent_queries += 1
 
+                        winston.debug("[#{that._concurrent_queries} concurrent]  rethink: query -- '#{query_string}'")
+                        if that._concurrent_queries > that._concurrent_warn
+                            winston.debug("rethink: *** concurrent_warn *** CONCURRENT WARN THRESHOLD EXCEEDED!")
+
+                        if that._concurrent_error and that._concurrent_queries > that._concurrent_error
+                            winston.debug("rethink: *** concurrent_error *** CONCURRENT ERROR THRESHOLD #{that._concurrent_error} EXCEEDED -- FAILING QUERY")
+                            that._concurrent_queries -= 1
+                            cb("concurrent_error")
+                            return
+
                         # choose a random connection
                         id = misc.random_choice(misc.keys(that._conn))
                         conn = that._conn[id]

                        if that._error_thresh
                            error_timer   = setTimeout(error_too_long,   that._error_thresh*1000)

                        winston.debug("[#{that._concurrent_queries} concurrent]  rethink: query -- '#{query_string}'")
                        if that._concurrent_queries > that._concurrent_warn
                            winston.debug("rethink: *** concurrent_warn *** CONCURRENT WARN THRESHOLD EXCEEDED!")
                        g = (err, x) ->
                            report_time = ->
                                that._concurrent_queries -= 1

            all_hosts: false      # if true, finds all hosts based on querying the server then connects to them
            warning  : 30          # display warning and stop using connection if run takes this many seconds or more
            error    : 10*60       # kill any query that takes this long (and corresponding connection)
            concurrent_warn  : 150  # if number of concurrent outstanding db queries exceeds this number, put a concurrent_warn message in the log.
            concurrent_error : 200  # if nonzero, and this many queries at once, any query instantly fails!
            mod_warn : 2           # display MOD_WARN warning in log if any query modifies at least this many docs
            cache_expiry  : 15000  # expire cached queries after this many milliseconds (default: 15s)
            cache_size    : 250    # cache this many queries; use @...query.run({cache:true}, cb) to cache result for a few seconds
