Express server res.json("") take a lot of time

Question

I have nodejs app, I using typescript and Express server and express-session.

I have also routing function that get request from the client and response.

private async changeVis(req: express.Request, res: express.Response) {
   Let mySession=._deepClone(req.session['blah']);
   MyModule.changeViz(mySession).then(function(myRes){
    req.session["blah"] = myRes;

    console.log('before res.json');        
    res.json("");
    console.log('after res.json');
}); 

My problem is, that the line

 res.json("");

take somthing like 5 seconds, the delta between the time 'before res.json' appear and 'after res.json' appear is plus minus 5 seconds.

Now, when I not use session and the function is like :

private async changeVis(req: express.Request, res: express.Response) {
   MyModule.changeViz().then(function(){;
    console.log('before res.json');        
    res.json("");
    console.log('after res.json');
}); 

there is no delta, 'after res.json' appear immediately after 'before res.json'.

I try to add res.end(), but it's not help.

Someone can help?

Answer 1

Because you declared the function to be async. your res object will wait until all of the processes in the function will end . You can either make all your other functions after res.end(); Or remove the async from the function