Hello,
I'm currently testing a quite simple setup. Haproxy in front of 1 nginx
and 3 backends running a node.js application. Nginx serves static files
only and I have no issue with it.
There are 2 frontends, one for http and one for https.
In a standard configuration the browser will ask for a http dynamic page
then once the page loaded the browser will establish a https websocket
connection for a long time. It also works fine.
However to avoid any overload on node.js backend servers I would like to
limit the number of simultaneous connections on these. It's possible to
define maxconn in backends and that's fine but if the backend server is
overloaded the connecting user is not warned as it may happen while
establishing the websocket connection. The user cannot see the 503 error
in this case.
So I would like to warn the user connecting that there is any kind of
overload on the server if the backends limits are (nearly) reached.
Right now it cannot be done inside the application so I wonder if there
is a way to do that in the frontends before any request is sent to the
backends. A kind of dynamic 503 page may be a solution here. It should
be triggered only if there is a threshold reached on backends.
There is an extract of the current test setup :
frontend www
bind 0.0.0.0:80
mode http
acl is_static_dev path_beg /application
acl is_dynamic_dev path_beg /nodejs/application
use_backend websocket_backend_dev if is_dynamic_dev
use_backend www_backend_dev if is_static_dev
default_backend www_backend
frontend wwws
bind 0.0.0.0:443 ssl crt /etc/haproxy/ssl/server.pem
mode http
acl is_static_dev path_beg /application
acl is_dynamic_dev path_beg /nodejs/application
use_backend websocket_backend_dev if is_dynamic_dev
use_backend www_backend_dev if is_static_dev
default_backend www_backend
backend www_backend_dev
mode http
option forwardfor
server web1 127.0.0.1:81 weight 1 maxconn 8192
backend www_backend
mode http
option forwardfor
server web1 127.0.0.1:81 weight 1 maxconn 8192
backend websocket_backend_dev
mode http
option forwardfor
option http-server-close
option forceclose
no option httpclose
option persist
option redispatch
fullconn 20000
cookie rd insert indirect nocache
balance roundrobin
server s1 127.0.0.1:3026 weight 95 maxconn 100 cookie s1
server s2 127.0.0.1:3030 weight 100 maxconn 100 cookie s2
server s3 127.0.0.1:3031 weight 100 maxconn 100 cookie s3
BTW: Thank's a lot for HAProxy, it's a very good software.
--
Best regards,
Artur
