Dropped WebSocket connection in Rancher's LoadBalancer - websocket

Question

I have simple WebSocket connection from my browser to a service inside Rancher.
I tried to connect to the service in 2 ways:
1) directly to the service:
browser ---> service
2) via Rancher's Load Balancer:
browser ---> Load Balancer ---> service
In the first case everything is fine: the connection is established and the messages are sent through it.
In the 2nd case the connection is dropped in after ~50s. Messages are send through the connection correctly in both directions.
What is the reason?
EDIT: I tested in on ws and wss protocol. In both cases there is the same issue.

Answer 1

Rancher Load Balancer internally uses HAProxy, which can be customized to your needs.
Here is an example HAProxy config for websockets:
global
maxconn 4096
ssl-server-verify none
defaults
mode http
balance roundrobin
option redispatch
option forwardfor
timeout connect 5s
timeout queue 5s
timeout client 36000s
timeout server 36000s
frontend http-in
mode http
bind *:443 ssl crt /etc/haproxy/certificate.pem
default_backend rancher_servers
# Add headers for SSL offloading
http-request set-header X-Forwarded-Proto https if { ssl_fc }
http-request set-header X-Forwarded-Ssl on if { ssl_fc }
acl is_websocket hdr(Upgrade) -i WebSocket
acl is_websocket hdr_beg(Host) -i ws
use_backend rancher_servers if is_websocket
backend rancher_servers
server websrv1 <rancher_server_1_IP>:8080 weight 1 maxconn 1024
server websrv2 <rancher_server_2_IP>:8080 weight 1 maxconn 1024
server websrv3 <rancher_server_3_IP>:8080 weight 1 maxconn 1024
Reference: https://rancher.com/docs/rancher/v1.6/en/installing-rancher/installing-server/basic-ssl-config/#example-haproxy-configuration
Only the relevant config can be used in "Custom haproxy.cfg" section of the LB.
See screenshot:
Here is the link for more documentation for custom haproxy in Rancher: https://rancher.com/docs/rancher/v1.6/en/cattle/adding-load-balancers/#custom-haproxy-configuration