proxy_response cant forward the app heartbeat packet to client

[guanglinlv]

hi,
I find proxy_response cant send the app heartbeat packet(only 6 bytes) to client immediately because using ngx.print. so i have to invoke ngx.flush after print. may i have your some good advice?
see http://wiki.nginx.org/HttpLuaModule#ngx.flush

[pintsized]

Hi. Well proxy_response is really just a convenience function, requested by users. If you need greater control, then it's quite trivial to implement your own version, and decide to call ngx.flush when you wish. If your app has a 6 byte heartbeat then you can test for that in your code, and decide to flush this immediately. Sounds like you're doing this already?

[guanglinlv]

yes,i had to invoked ngx.flush for my streaming output, but I'm not sure that delaying send is decided by ngx.print or nginx, how to config it ?

[pintsized]

It might be best to ask on the OpenResty mailing list, since others may have more experience with this than me. But my understanding is that ngx.print will push data to the Nginx output chain and it's up to Nginx to buffer however it wants. If however you call ngx.flush in synchronous mode after ngx.print, then the print effectively becomes synchronous (though remaining non-blocking to the Nginx event loop), and the data is sent to the system send buffer more directly.

ngx.print(chunk)
ngx.flush(true)

Beyond this, it is up to Nginx to get those bytes out on the wire, and I'm not sure if there's any more control available for this.

https://github.com/openresty/lua-nginx-module#ngxflush
https://github.com/openresty/lua-nginx-module#ngxprint

[guanglinlv]

ok, thanks for your patiently replay.