javascript - Polling interval for xhr for socket.io 1.0 -

how set polling interval xhr fallback socket.io 1.0? looks polls every second when not in websocket mode i'd prefer if polling interval every 2 seconds reduce load on server.

i read through documentation both socket.io , engine.io options object couldn't find in there set polling interval.

io.set("polling duration", 2); 

although "set" gone. think have in server initialization

var socket = require('socket.io')({     "polling duration": 2 });