res.send 令牌然后重定向

Question

I have an express app that upon calling a get request immediately returns a string token, then runs a python code. The python code after some time creates a json file that I need to send in another post request.

This python code may be called by different users that's why i need to assign them a token a soon as the app is called. In the post request i'll also be modifying the json file and then sending it back

I'm trying to do res.send the token and then res.redirect to the post request, but i know it's impossible. Is there any other way i could send the token or redirect to the post request?

app.get('/', (req, res) =>{
     res.send(token())
     runPython((code)=>{ 

     *takes around 10 sec*

       res.redirect('/post')}}

app.post('/post', (req, res)=>{

     *do stuff to file*

     res.sendFile()

Answer 1

You cannot send multiple responses back to the client separated in time. You get ONE http response. So, once you've done res.send(token()) , then that http request is done. You can't send any more data as part of that http request.

As you describe things, here are some of your options:

1. Combine both into one response. Wait to send the token until you have the python response too and then send them both in one JSON response. You won't be able to do a res.redirect() if you're also sending data back. So, you could send the redirect location back in the JSON and have the client manually do the redirect (by just setting window.location to a new URL). Presumably, there is client-side Javascript on the receiving end of this anyway since some form of code has to receive the token anyway to do something useful with it.

2. Use websocket/socket.io connection for subsequent server-initiated communication. Have the client connect a webSocket or socket.io connection. You can then response with the token and then later when the python has finished, you can send additional data over the websocket or socket.io connection. This will require additional code to be able to associate a particular websocket/socket.io connection with the client that made this request so you can tell which websocket/socket.io connection for this request to send a notification over.

3. Client-side polling for completion of python operation. Have the server send back the token and also send it some sort of request ID and then the client can poll the server every few seconds to ask the server if that python operation for that request ID is now done. When it gets a response from the server that the python is now done, then the client can manually redirect itself to /post to fetch the final data.