express session-file-store session count not view-count

I am using express-session for session management in my node js application. using session-file-store. I want to count the number of sessions, to restrict new sessions after maxAllowed sessions.

Is there any method supported for doing that? I dont want view count, I just want session count.

To count session using session-file-store can be done as shown below..

//file store parameters
var sess_options = {
path: "/tmp/sessions/",
useAsync: true
};
// sess_count variable
var sess_count = 0;

var file_store = new FileStore(sess_options);
router.use(session({
store : file_store,
resave : false,
saveUninitialized : true,
secret : 'asts123',
rolling : false,
cookie : {  httpOnly: false,
secure : true,
maxAge : 60000
}
}));

router.use(function(req, res, next) {
file_store.length(function session_count(a,len) {
sess_count = len;
console.log("Total active session count is " + sess_count);
console.log("============");
});
return next();
});