Sharing cache in multiple instances with nginx

Question

I will context my question...

I have a Node.js web app working fine. I have a load balancer in AWS (Elastic Load Balancing, Classic Mode) with an Auto Scaling Group with multiple EC2 instances.

Each EC2 instance has a Nginx reverse proxy installed which work fine with PM2 and Node.js (Express). I use Nginx to caching static files, caching request, https, and another stuff.

I need to know how can I share a cache between all the instances using Nginx, and not use each one the memory cache in each machine. I would like to use Memcache o Redis, but I need to choose one, I prefer Redis.

This is the example how I'm working in this moment (just important code):

proxy_cache_path /cache/nginx levels=1:2 keys_zone=cache_zone_name:10m;

location / {
            #root   html;
            #index  index.html index.htm;

            #Config proxy inverse cache
            proxy_pass http://localhost:3000;
            proxy_http_version 1.1;
            proxy_set_header Upgrade $http_upgrade;
            proxy_set_header Connection 'upgrade';
            proxy_set_header Host $host;
            proxy_cache_bypass $http_upgrade;

            # Add cache debugging header
            add_header X-Cache-Status $upstream_cache_status;

            # Configure cache
            proxy_cache        cache_zone_name;
            proxy_cache_valid  any 1m;
            proxy_cache_key    $scheme$host$request_uri;

        }

I have found this question in ServerFault without no answer.

Thanks!

Edit: Important note, I need a solution that does not affect the performance :)

score 0 · Answer 1 · answered Sep 16 '17 at 17:43

nginx stores cached data in files but mapping of cache_keys (unique identifier for a url) to content location is stored in a memory

Eg: when you access url http://localhost/index.html which means content of index.html will be stored in /cache/nginx/c/29/b7f54b2df7773722d382f4809d65029c and md5 of cache_key to location will be stored in memory (md5(httplocalhostindex.html) -> /cache/nginx/c/29/b7f54b2df7773722d382f4809d65029c)

Nginx can not keep this mapping on local storage or shared memory (redis/memcached) which will impact caching performance

Reference: http://nginx.org/en/docs/http/ngx_http_proxy_module.html (search for keyword keys_zone)

Sharing cache in multiple instances with nginx

1 Answers1