Build and customize your CDN

When you need your own CDN

• when you want to save money, and running costs even when using inexpensive CDNs like BunnyCDN are several hundred dollars a month
• if we want to get a permanent cache or a cache without neighbors on the server and channel
• in the region you need, CDN services have no points of presence
• any special content delivery settings required
• we want to accelerate the delivery of dynamic content by placing closer to the users of the production server
• there is a concern that a third-party CDN service may unlawfully collect or use information about user behavior (hi to services without GDPR-compliant) or engage in other illegal actions

What you need to run

• . ,
• geoDNS . , ,

Configure geoDNS

1. Defines the IP of the client that sent the DNS request, or the IP of the recursive DNS server that is used to process the client request. These recursive servers are usually DNS providers.
2. By IP client knows his country or region. For this, GeoIP bases are used, of which there are a great many today. There are some good free options .
3. Depending on the location of the client, he gives him the IP address of the nearest CDN server.

• louDNS from $ 9.95 / month , GeoDNS tariff, by default there is one DNS Failover
• Zilore from $ 25 / month , DNS Failover enabled
• Amazon Route 53 from $ 35 / mo for 50M net geo-requests. DNS failover is charged separately
• DNS Made Easy from $ 125 / mo , there are 10 DNS Failover
• Cloudflare , Geo Steering Feature Available in Enterprise Rates

Install SSL Certificates

root@cdn:~# wget -O - https://get.acme.sh | bash; source ~/.bashrc

CLOUDNS_AUTH_ID=<auth-id>
CLOUDNS_AUTH_PASSWORD="<>"

root@cdn:~# acme.sh --issue --dns dns_cloudns -d cdn.sayt.in --reloadcmd "service nginx reload"

root@cdn:~# mkdir -p /root/.acme.sh/cdn.sayt.in/
root@cdn:~# scp -r root@199.247.18.199:/root/.acme.sh/cdn.sayt.in/* /root/.acme.sh/cdn.sayt.in/

scp -r root@199.247.18.199:/root/.acme.sh/cdn.sayt.in/* /root/.acme.sh/cdn.sayt.in/ && service nginx reload

Install and configure Nginx

root@cdn:~# apt update
root@cdn:~# apt install nginx

user www-data;
worker_processes auto;
pid /run/nginx.pid;

events {
    worker_connections 4096;
    multi_accept on;
}

http {
    sendfile on;
    tcp_nopush on;
    tcp_nodelay on;
    types_hash_max_size 2048;

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

    access_log off;
    error_log /var/log/nginx/error.log;

    gzip on;
    gzip_disable "msie6";
    gzip_comp_level 6;
    gzip_proxied any;
    gzip_vary on;
    gzip_types text/plain application/javascript text/javascript text/css application/json application/xml text/xml application/rss+xml;
    gunzip on;            

    proxy_temp_path    /var/cache/tmp;
    proxy_cache_path   /var/cache/cdn levels=1:2 keys_zone=cdn:64m max_size=20g inactive=7d;
    proxy_cache_bypass $http_x_update;

server {
  listen 443 ssl;
  server_name cdn.sayt.in;

  ssl_certificate /root/.acme.sh/cdn.sayt.in/cdn.sayt.in.cer;
  ssl_certificate_key /root/.acme.sh/cdn.sayt.in/cdn.sayt.in.key;

  location / {
    proxy_cache cdn;
    proxy_cache_key $uri$is_args$args;
    proxy_cache_valid 90d;
    proxy_pass https://sayt.in;
    }
  }
}

• max_size - cache size not exceeding available disk space
• inactive - storage time for cached data that no one accessed
• ssl_certificate and ssl_certificate_key - paths to SSL certificate and key files
• proxy_cache_valid - storage time for cached data
• proxy_pass - the address of the original server from which the CDN will request files for caching. In our example, this is sayt.in

• if the request is not repeated within 7 days, then the data will be deleted from the cache after this period
• if the request is repeated at least once every 7 days, then the data in the cache will be considered outdated after 90 days and at the next request Nginx will update it by taking it from the original server

root@cdn:~# service nginx reload

Checking the operation of CDN

#!/bin/bash
if [ -z "$1" ]
then
    echo "Purging all cache"
    rm -rf /var/cache/cdn/*
else
    echo "Purging $1"
    FILE=`echo -n "$1" | md5sum | awk '{print $1}'`
    FULLPATH=/var/cache/cdn/${FILE:31:1}/${FILE:29:2}/${FILE}
    rm -f "${FULLPATH}"
fi

root@cdn:~# ./purge.sh /test.jpg

Instead of conclusions

• To increase CDN fault tolerance, it is recommended to configure DNS Failover, which helps to quickly change A record in case of server failure. This is done in the control panel of the DNS records of the domain
• CDN, . CDN, 6-7 : , (), (), , ,
• CDN. , , -
• , ,
• Try to check pings from different places to your servers. So you can see the regions closest to the CDN points and configure GeoDNS correctly
• Depending on the tasks, it is not out of place to configure Nginx for specific caching requirements and taking into account the load on the server. The articles about the Nginx cache - here and the acceleration of work under heavy loads: here and here helped me a lot.