What does fastcgi_keep_conn do?

[addis_a]

Hi, I would like nginx to serve all requests of a given TCP connection
to
the same FCGI server. If a new TCP connection is established, then nginx
would select the next UDS FCGI server in round-robin fashion.

Can this be achieved with NGINX, and if yes, how?

I thought turning on fastcgi_keep_conn on would achieve this goal, but
it is
not what happened. My obervation was that each FCGI server took turn
receiving a new request even if all the requests are from the same TCP
connection.

I had:

upstream backend {
server unix:/tmp/fastcgi/socket1 …;
server unix:/tmp/fastcgi/socket2 …;
keepalive 32;
}

server {
…
location {
fastcgi_keep_conn on;
fastcgi_pass backend;
}

Thank you.

Posted at Nginx Forum:
http://forum.nginx.org/read.php?2,257508,257508#msg-257508

[nginxuser100]

‘Keep connection’ does not mean what you think it means.

That does not tie a client connection to a backend connection. To do
that,
you will need stuff like ip_hash
http://nginx.org/en/docs/http/ngx_http_upstream_module.html#ip_hash or
more advenced session mechanisms (which are sadly not available in
FOSS…
yet?).

Read the docs on fastcgi_keep_conn
http://nginx.org/en/docs/http/ngx_http_fastcgi_module.html#fastcgi_keep_conn,
which says it ensures the FastCGI connection is not close after being
used,
which is the normal way of doing it. Use that in relation with keepalive
http://nginx.org/en/docs/http/ngx_http_upstream_module.html#keepalive,
as
instructed.

That means that connections to the backend will remain open after being
open, so the next time the webserver addresses to them, they won’t need
to
open a new connection to them.

B. R.

[nginxuser100]

Thank you, that did the trick.

Posted at Nginx Forum:
http://forum.nginx.org/read.php?2,257508,257619#msg-257619