Help using a load balancer with Mastodon

Hi, I’m setting up an instance with a load balancer and I have some questions. This is my setup:

  • 1 VM running Nginx as load balancer
  • 1 VM running Puma
  • 1 VM running Node.js streaming
  • 1 VM running Postgres and Redis
  • I plan to add more nodes once this works.

My questions:

  1. Is Round Robin suitable for Puma? I’m unclear how sessions work.
  2. Is Round Robin suitable for the Streaming server?
  3. Do you serve static files directly from the load balancer node?

Below is my configuration. I would appreciate any general suggestions or tips might have. Thanks!

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

proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=CACHE:10m inactive=7d max_size=1g;

upstream puma {
  server 10.0.0.1:3000;
}

upstream streaming {
  ip_hash;
  server 10.0.0.2:4000;
}

server {
  listen 80;
  listen [::]:80;
  server_name mysite.com;
  root /home/soapbox/live/public;
  location /.well-known/acme-challenge/ { allow all; }
  location / { return 301 https://$host$request_uri; }
}

server {
  listen 443 ssl http2;
  listen [::]:443 ssl http2;
  server_name mysite.com;

  ssl_protocols TLSv1.2;
  ssl_ciphers HIGH:!MEDIUM:!LOW:!aNULL:!NULL:!SHA;
  ssl_prefer_server_ciphers on;
  ssl_session_cache shared:SSL:10m;
  ssl_certificate     /etc/letsencrypt/live/mysite.com/fullchain.pem;
  ssl_certificate_key /etc/letsencrypt/live/mysite.com/privkey.pem;

  keepalive_timeout    70;
  sendfile             on;
  client_max_body_size 80m;

  root /home/soapbox/live/public;

  gzip on;
  gzip_disable "msie6";
  gzip_vary on;
  gzip_proxied any;
  gzip_comp_level 6;
  gzip_buffers 16 8k;
  gzip_http_version 1.1;
  gzip_types text/plain text/css application/json application/javascript text/xml application/xml application/xml+rss text/javascript;

  add_header Strict-Transport-Security "max-age=31536000";

  location / {
    try_files $uri @proxy;
  }

  location ~ ^/(emoji|packs|system/accounts/avatars|system/media_attachments/files) {
    add_header Cache-Control "public, max-age=31536000, immutable";
    add_header Strict-Transport-Security "max-age=31536000";
    try_files $uri @proxy;
  }

  location /sw.js {
    add_header Cache-Control "public, max-age=0";
    add_header Strict-Transport-Security "max-age=31536000";
    try_files $uri @proxy;
  }

  location @proxy {
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto https;
    proxy_set_header Proxy "";
    proxy_pass_header Server;

    proxy_pass http://puma;
    proxy_buffering on;
    proxy_redirect off;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection $connection_upgrade;

    proxy_cache CACHE;
    proxy_cache_valid 200 7d;
    proxy_cache_valid 410 24h;
    proxy_cache_use_stale error timeout updating http_500 http_502 http_503 http_504;
    add_header X-Cached $upstream_cache_status;
    add_header Strict-Transport-Security "max-age=31536000";

    tcp_nodelay on;
  }

  location /api/v1/streaming {
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
    proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    proxy_set_header X-Forwarded-Proto https;
    proxy_set_header Proxy "";

    proxy_pass http://streaming;
    proxy_buffering off;
    proxy_redirect off;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection $connection_upgrade;

    tcp_nodelay on;
  }

  error_page 500 501 502 503 504 /500.html;
}