Redis & nginx configuration for websocket/actionCable

Start redis server => redis-server
redis console => redis-cli

view available databases => config get databases

pubsub channels global*
pubsub channels global_notification_2
pubsub channels global_notification

pubsub channels * => Lists all the available channels
pubsub numsub global_notification_2 => returns the number of subscribers

From unix command line directly

redis-cli PUBSUB CHANNELS
redis-cli PUBSUB NUMSUB global_notification_2

[root@api prod-openmednet-api]# redis-cli PUBSUB CHANNELS
1) "_action_cable_internal"
2) "global_notification_2"

[root@api prod-openmednet-api]# redis-cli PUBSUB CHANNELS global_notification_2
1) "global_notification_2"

[root@api prod-openmednet-api]# redis-cli PUBSUB NUMSUB global_notification_2

1) "global_notification_2"

2) (integer) 2

NGINX configuration: 

worker_processes  auto;

worker_rlimit_nofile 500000;  #=> refer RLIMIT_NOFILE

server {

        error_log  logs/dev/error.log  warn;

        listen       80 default_server;

        server_name  devapi.openmednet.org;

        root         /home/rubyapps/OMNR5/OpenMedNet-R5/dev-openmednet-api/public;

        rails_env development;

        passenger_enabled on;

        if ($http_user_agent ~* LWP::Simple|BBBike|jorgee) {

          return 403;

        }

        access_log  logs/dev/host.dev.access.log  main;

        error_page   500 502 503 504  /50x.html;

        location = /50x.html {

            root   html;

        }

        location /cable {

            passenger_app_group_name omndevapi_action_cable;

            passenger_force_max_concurrent_requests_per_process 0;

        }

    }

setting RLIMIT_NOFILE

step: 1

vi /etc/security/limits.conf

add the following two lines at the end of the file 

* soft nofile 120000

* hard nofile 120000

ref: https://caradede.blogspot.com/2017/12/how-to-solve-centos-7-nofile-limit-nginx.html

mkdir  /etc/systemd/system/nginx.service.d

vi /etc/systemd/system/nginx.service.d/nofile_limit.conf

have the following two lines in that file 

[Service]

LimitNOFILE=500000

systemctl daemon-reload systemctl restart nginx.service

or simply set

setsebool -P httpd_setrlimit 1

And then have the following 3 lines of code @ /etc/sysctl.conf

net.core.somaxconn = 4096

fs.file-max = 120000

vm.overcommit_memory = 1

Then don't forget to restart the machine to apply the settings. AFter restart 

check "ulimit -n" it should match fs.file-max above 

this command too will match 

cat /proc/$(cat /opt/nginx/logs/nginx.pid)/limits | grep open.files