Server Sent Events in Google Compute Engine - google-compute-engine

Question

I'm trying to get an app that uses Server Sent events working on Google Compute Engine, when SSH'd into the box I can view them, but not externally via the ephermeral IP, aka
curl 0.0.0.0/route
works from inside the box but
curl xx.xx.xx.xx/route
just hangs, looking at the headers from other routes there seems to be some sort of cacheing proxy in between the box and the outside word that is preventing server sent events from getting out because the the connection hasn't completed, there is a similar issue with nginx until you set proxy_cache off, but as far as I can tell there is no documentation for configuring the proxy that compute engine uses.
Is it possible to do server sent events from Google Compute Engine and if so what do you have to do to get it to work?
edit:
Request is created with the browser EventSource object, so it has the default headers which look to be Accept:text/event-stream, Cache-Control:no-cache, plus Referer and User-Agent.
The headers I add are Content-Type:text/event-stream, Cache-Control:no-cache, and Connection:keep-alive.
When run in AWS all is fine when I run it behind nginx assuming I modify the config appropriately.
In Google Compute Engine other pages load fine but the route with Server Sent Events just hangs never even receiving headers. The reason I suspect google is sticking a proxy between the GCE box and the outside world is the addition of Via:HTTP/1.1 proxy10205 headers.

Answer 1

There may be magic on the lower network layers but there is no (transparent or otherwise) proxy between your VM and the internet on GCE for the external IP. I'm not sure where the Via header comes from, doesn't the browser/client have a proxy configured?
External IPs are not configured in the most straightforward way on GCE though which might be tripping up something in the stack. I think for external IPs, the external IP itself does not appear anywhere in the VM config, it's translated to the VM internal IP by 1-1 NAT. Loadbalanced IPs do end up on the host with external IP visible though (even though even these are configured in a funny way).
Even though I don't think anything should really care about the server IP for SSE, maybe try setting up a loadbalanced IP pointing to just that one instance and see if it works any better?

Answer 2

"Via:HTTP/1.1 proxy10205" in your HTTP response is not from Google Compute Engine.
The GCE does not strip out the Server-Sent-Events headers. I list the simple steps below which can help you to configure a demo Server-Sent Events on an GCE VM instance:
Create an GCE instance using CentOS image.
Install Apache web server and PHP:
$ sudo yum install httpd php
Create an index.html file with the HTML content from this page :
$ sudo vi /var/www/html/index.html
Create a PHP file called demo_sse.php in the www root directory ($ sudo vi /var/www/html/demo_sse.php ) with the following content:
<?php
header('Content-Type: text/event-stream');
header('Cache-Control: no-cache');
$time = date('r');
echo "data: The server time is: {$time}\n\n";
flush();
?>
Now visit the webpage. You can also verify the header using curl command:
$ curl -H "Accept:text/event-stream" --verbos http://<YOUR-GCE-IP ADDRESS>/demo_sse.php