在长时间轮询期间刷新NginX的SSL缓冲区

Question

I'm writing an app that uses long polling to push messages to clients. It doesn't end the request when it finishes sending a message though: it just flushes. It works fine, even when I proxy it through nginx and access it over the internet.

upstream app {
  server localhost:1000;
}

server {
    listen 80;    
    location / {
        proxy_pass http://app;
        client_max_body_size 20m;
        proxy_redirect off;
        send_timeout 86400;
        proxy_read_timeout 86400;
        proxy_buffering off;
        gzip off;
    }
}

That is, until I enable SSL on nginx. Then it won't flush anymore. I can work around this by setting ssl_buffer_size to 1, but this negatively impacts performance.

upstream app {
  server localhost:1000;
}

server {
    listen 443;
    ssl_certificate cert.pem;
    ssl_certificate_key key.pem;
    ssl_buffer_size 1;
    location / {
        proxy_pass http://app;
        client_max_body_size 20m;
        proxy_redirect off;
        send_timeout 86400;
        proxy_read_timeout 86400;
        proxy_buffering off;
        gzip off;
    }
}

I wrote my application in Go, and I'm using the standard Flush() from net/http. I tried using Hijack to get a regular TCP buffer and Flush() that, but it still didn't work.

Answer 1

This isn't a Go issues, but more a Nginx configuration issue. It's most probably Nginx who is holding back your data.

Your could try to disable proxy buffering to avoid this. Try:

server {
    listen 443;
    ssl_certificate cert.pem;
    ssl_certificate_key key.pem;
    ssl_buffer_size 1;

    proxy_buffering off;
}

P.S.: Not tested but give it a try.