ActionCable + Nginx + Puma and java.io.EOFException - ruby-on-rails

Question

I'm trying to connect to an ActionCable websocket and everything works fine running locally with just Puma and without nginx.
However, when I try to do the exact same thing on my staging environment, the connection is immediately closing after connecting. I am able to get the downstream welcome messages and maybe a ping.
However, the connection abruptly closes without any of the onClose callbacks so my guess is nginx is not letting the connection persist.
Here is my sites nginx configuration.
upstream app {
# Path to Puma SOCK file, as defined previously
server unix:/home/deploy/my-app/shared/tmp/sockets/puma.sock fail_timeout=60;
keepalive 60;
}
server {
listen 80;
server_name localhost;
# websocket_pass websocket;
root /home/deploy/my-app/current/public;
try_files $uri/index.html $uri #app;
location #app {
proxy_pass http://app;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header Host $http_host;
proxy_redirect off;
}
#location / {
# proxy_set_header X-Forwarded-Proto $scheme;
# proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
# proxy_set_header X-Real-IP $remote_addr;
# proxy_set_header Host $host;
# proxy_redirect off;
# proxy_http_version 1.1;
# proxy_set_header Connection '';
# proxy_pass http://app;
#}
location ~ ^/(assets|fonts|system)/|favicon.ico|robots.txt {
gzip_static on;
expires max;
add_header Cache-Control public;
}
location /cable {
proxy_pass http://app;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection "Upgrade";
}
error_page 500 502 503 504 /500.html;
client_max_body_size 4G;
keepalive_timeout 10;
}
I also found this error in nginx error logs:
2019/02/11 21:08:35 [error] 10233#10233: *2 recv() failed (104: Connection reset by peer) while proxying upgraded connection, client: x.x.x.x, server: localhost, request: "GET /cable/ HTTP/1.1", upstream: "http://unix:/home/deploy/wr-api/shared/tmp/sockets/puma.sock:/cable/", host: "x.x.x.x"

Answer 1

So after some time, we noticed that the staging environment cable.yml had this value for url:
url: <%= ENV.fetch("REDIS_URL") { "redis://localhost:6379/1" } %>
Removing that value and all other values except for adapter: staging fixed it for us.
New cable.yml staging config:
staging:
adapter: redis
Working!