Server-sent events not working

[davej]

It works for a period of time and then I get an error in the browser console: "net::ERR_INCOMPLETE_CHUNKED_ENCODING"… after this it stops working.

Works perfectly if I load the site directly (i.e. not through the proxy).

Code I'm using to proxy request/responses is simply:

proxy.web(req, res, { target = 'http://localhost:8888' });

Previous issue was: #357

[jcrugzz]

@davej would love to have a test case for this. Can you reproduce in a node only test so we could add that to our test suite? Thanks!

[aaronmaturen]

Hey friends,

SSE seems to be working for me, but I created a test and example for SSE here: #922

[davej]

@aaronmaturen: Thanks for that.

I was able to figure out what the issue is. node-http-proxy is timing out the response after 2 minutes of inactivity.

If you change the connection handler on line 57 of the sse example to the code below then you should be able to recreate it:

sse.on('connection', function(client) {
  client.res.setTimeout(0); // Disable timeout
  var count = 0;
  setTimeout(function(){
    client.send('message #' + count++);
  }, 1500);

  setTimeout(function(){
    client.send('message #' + count++);
  }, 150000);
});

On the proxy (8003), it times out after about 2 minutes (Chrome 46), with net::ERR_INCOMPLETE_CHUNKED_ENCODING and the second message is not received.

On the raw SSE server (9003), it doesn't time out and the second message is received.

Is there a way to get the proxy to respect the timeout characteristics of the SSE server

[aaronmaturen]

It looks like the ws proxy prevents the connection from timing out by setting the timeout option to 0; you may be able to the same with this one. I tried setting the timeout to 1000ms and it threw the error when I expected. When I set the timeout to 0 and the interval to 150000, chrome didn't throw the error again but the tab stopped showing the loading ticker after ~2minutes

//
// Basic Http Proxy Server
//
var proxy = new httpProxy.createProxyServer();
http.createServer(function (req, res) {
  proxy.web(req, res, {
    target: 'http://localhost:9003',
    timeout: 0 // prevent the proxy from killing the connection
  });
}).listen(8003);

[davej]

Yes, it's easy enough to fix when you know what's wrong, thanks for your help.

I guess I can close this issue unless it's worth considering setting the timeout to 0 for websocket and SSE connections? Or is that a bit too magical?

[aaronmaturen]

There is a setupSocket method in common.js that not only sets the timeout but also sets no delay and keep alive on the current socket. This is currently called in ws-incoming.js after the upgrade event has been emitted for web-sockets.

SSE has a specified Content-Type of text/event-stream but you wouldn't have that header until the server already had given you a response. It may be possible to look at what the request accepts and upgrade it based on that header, but it seems like somewhat of a specialized case.

[jimjaeger]

Any outlook for a fix or is a workaround available?

[rstudner]

Curious if anyone has gotten SSE events to work through the proxy?

I have a UI, hitting this proxy, over to a nodejs server wanting to do SSE.

In production/no proxy/using just nginx everything works great. But in my dev environment, trying to use this proxy, it never seems to let the events "get to the browser" (server 100% pushes them out etc).

and on the UI side, the sse connection resets every 2 minutes (which also doesn't happen in an environment not using this proxy

[thomas-hilaire]

I tried with the timeout: 0 option but I have exactly the same issue than @rstudner
Note that I continue to get the connection:close header in the devtools, the timeout option does it job?

[aaronmaturen]

I've been using this proxy with SSE for about the last year, there's an example at examples/http/sse.js that you can start and then go to http://127.0.0.1:8003 to see it being proxied with all the events every 1500ms.

If I change the proxy to have a timeout of 1000ms I see the initial :ok but then no results from the target server... but I'd expect that with the timeout being shorter than the event interval.

Could either of you provide a modified version of the sse example that doesn't send back responses so we can try to figure out what's going wrong?

[thomas-hilaire]

I finally found what was the issue. It comes from the https://webpack.js.org/configuration/dev-server/#devserver-compress option that was enabled. I used the compress: false option but I didn't noticed that the --compress flag was passed in the command-line.

It is now working, thx! 👍

[tiagocoutinho]

I' ve been fighting with this one for the last couple of days. Setting compress: false solved the problem for me. Thanks @thomas-hilaire!

[shijunti19]

I can't solve it. I'm nginx agent webpack vue2

[joshiste]

I guess this describes the culprit with the compression: https://github.com/expressjs/compression#server-sent-events

Is there a way to eagerly flush the response after each chunk recieved?