Use NGINX to cache API Response

Here is the difference form cahced slow controller and not chached.

Screen.Recording.2022-10-03.at.10.21.00.mov

Incredibles preformances on local machine.

Nginx

The hearth of nginx cache is in this file :

fastcgi_cache_path  /var/cache/nginx/api  levels=1:2  keys_zone=apicache:60m;
fastcgi_cache_key   $scheme://$host$saved_uri$is_args$args;  # we must use the query string too, because it identifies the apicache

server {
    listen 80;
    server_tokens off;
    client_max_body_size 20M;

    server_name _;
    access_log off;

    root /app/public;

    include fastcgi_params;  # putting this ahead, to let locations override the params


    location / {
        set $saved_uri $uri;  # NOTE we need this because the $uri is renamed later to "index.php", so we loose the "original" one
        try_files /dev/null @rewriteapp;
    }

    location ~ ^/(ping|health)$ {
        rewrite ^(.*)$ /index.php/$1 last;
    }

    location @rewriteapp {
        rewrite ^(.*)$ /index.php/$1 last;
    }

    location ~ ^/(index)\.php(/|$) {
        include fastcgi_params;  # putting this ahead, to let locations override the params

        fastcgi_cache_bypass        $http_x_purge;
        fastcgi_cache apicache;  # for fastcgi do not use proxy_cache
        fastcgi_cache_methods GET;

        fastcgi_param REQUEST_URI $saved_uri;  ## IMPORTANT By default fastcgi_params, it takes $request_uri (generating infinte loop because of ssi inclusion)
        fastcgi_param QUERY_STRING $args; ## query params
        fastcgi_pass php-fpm:9000;
        fastcgi_split_path_info ^(.+\.php)(/.*)$;

        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        fastcgi_param DOCUMENT_ROOT $document_root;
        fastcgi_param REQUEST_METHOD  $request_method;
        fastcgi_param CONTENT_TYPE    $content_type;
        fastcgi_param CONTENT_LENGTH  $content_length;
        fastcgi_read_timeout 300;
        internal;
    }
}

We use the cache only for GET requests, so please use the correct API-REST convention.

We save the URL before send it to fast-cgi and we use it as key.

We send some more helpful headers to backend.

Cache params :

• path : /var/cache/nginx/api
• levels=1:2 : we use folder structure to create efficent file access
• keys_zone=apicache:60m : name of cache apicache and ttl of 60min

PURGE

if you have a client that should have the must recent information (for example admin panel that modify some data), you can use this header client side to not use the cache :

x-purge: true

for example :

This curl continue cache the response (3ms response):

curl --location --request GET 'http://localhost:9999/cache'

and this one not use the cache (2.18s response, 180ms of symfony):

curl --location --request GET 'http://localhost:9999/cache' \
--header 'x-purge: true'

With the last one we have the more recent data and also cache the last one.

PHP

The only thing you have to do is set this attribute in your code :

#[HttpCacheable(maxAge: 3600)]

If you don't set the maxAge a default value of 3600s is taken. Set more the 1H is not necessary, nginx will revalidate the cache in any case.

There is a ResponseEventHandler that intercept the response and add cache header if necessary.

On client side you can see if a response can be a cached response analyzing the headers : if exists this one X-Webserver-Cache the response could be cached.

If you sand the header x-purge: true you still see the X-Webserver-Cache but it is a fresh response (cached for the next call).