Load balancing

This chapter shows how to deal with persistent connection load balancing.

caution

Regardless which reverse proxy / load balancer you are using make sure that you tuned open file limit for its process too since it will also need to handle many persistent connections. See Infrastructure tuning.

Nginx configuration

Although it's possible to use Centrifugo without any reverse proxy before it, it's still a good idea to keep Centrifugo behind mature reverse proxy to deal with edge cases when handling HTTP/Websocket connections from the wild. Also you probably want some sort of load balancing eventually between Centrifugo nodes so that proxy can be such a balancer too.

In this section we will look at Nginx configuration to deploy Centrifugo.

Minimal Nginx version – 1.3.13 because it was the first version that can proxy Websocket connections.

There are 2 ways: running Centrifugo server as separate service on its own domain or embed it to a location of your web site (for example to /centrifugo).

Separate domain for Centrifugo

upstream centrifugo {
    # uncomment ip_hash if using SockJS transport with many upstream servers.
    #ip_hash;
    server 127.0.0.1:8000;
}

map $http_upgrade $connection_upgrade {
    default upgrade;
    ''      close;
}

#server {
#	listen 80;
#	server_name centrifugo.example.com;
#	rewrite ^(.*) https://$server_name$1 permanent;
#}

server {

    server_name centrifugo.example.com;

    listen 80;

    #listen 443 ssl;
    #ssl_protocols TLSv1 TLSv1.1 TLSv1.2;
    #ssl_certificate /etc/nginx/ssl/server.crt;
    #ssl_certificate_key /etc/nginx/ssl/server.key;

    include /etc/nginx/mime.types;
    default_type application/octet-stream;

    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    gzip on;
    gzip_min_length 1000;
    gzip_proxied any;

    # Only retry if there was a communication error, not a timeout
    # on the Centrifugo server (to avoid propagating "queries of death"
    # to all frontends)
    proxy_next_upstream error;

    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Scheme $scheme;
    proxy_set_header Host $http_host;

    location /connection {
        proxy_pass http://centrifugo;
        proxy_buffering off;
        keepalive_timeout 65;
        proxy_read_timeout 60s;
        proxy_http_version 1.1;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Scheme $scheme;
        proxy_set_header Host $http_host;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection $connection_upgrade;
    }
    
    location / {
        proxy_pass http://centrifugo;
    }

    error_page   500 502 503 504  /50x.html;

    location = /50x.html {
        root   /usr/share/nginx/html;
    }
}

Embed to a location of web site

upstream centrifugo {
    # uncomment ip_hash if using SockJS transport with many upstream servers.
    #ip_hash;
    server 127.0.0.1:8000;
}

map $http_upgrade $connection_upgrade {
    default upgrade;
    ''      close;
}

server {

    # ... your web site Nginx config

    location /centrifugo/ {
        rewrite ^/centrifugo/(.*)        /$1 break;
        proxy_pass http://centrifugo;
        proxy_pass_header Server;
        proxy_set_header Host $http_host;
        proxy_redirect off;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Scheme $scheme;
    }

    location /centrifugo/connection {
        rewrite ^/centrifugo(.*)        $1 break;
        proxy_pass http://centrifugo;
        proxy_buffering off;
        keepalive_timeout 65;
        proxy_read_timeout 60s;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Scheme $scheme;
        proxy_set_header Host $http_host;
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection $connection_upgrade;
    }
}

worker_connections

You may also need to update worker_connections option of Nginx:

events {
    worker_connections 65535;
}