PHP caching / NOT REVERSE PROXY CACHING

This document is about caching content on each machine not the proxy they are connected to.

Difference between reverse proxy caching and PHP caching

Reverse proxy cache

Prefix: proxy_cache_.

PHP caching

Prefix: fastcgi_cache_.

Setup the cache

In this tutorial we will set 2 caches:

one for not authorized users that expires after 1 hour
and one for authorized users that expires after 5 minutes.

Define those caches in the nginx.conf

fastcgi_cache_path /tmp/cache_1h levels=1:2 keys_zone=cache_1h:100m max_size=100m inactive=1h;
fastcgi_cache_path /tmp/cache_5m_auth levels=1:2 keys_zone=cache_5m_auth:100m max_size=100m inactive=5m;

Explanation

/tmp/cache_1h - where to store specifc cache files.
levels=1:2 - structure cache directories in 2 levels like a/b/cccccccccccc.
max_size - total amount of cache directory’s size. If I understand correctly will consume same amount of memory to keep track of those files.
inactive - time the cache expires.

Tell NGINX that we want to control cache by our own

By default NGINX cache reacts to Cache headers

fastcgi_ignore_headers Cache-Control Expires Set-Cookie;

Define allowed request methods that can be cached

In case if we don’t want to cache PUT (update) requests or others.

fastcgi_cache_methods GET HEAD; # Only GET and HEAD methods apply

Use the 1 hour unauth cache for a static content like text

See a working example.

Duplicate index.php to index_cached_1h.php. To understand why this is necessary read Why conditional requests are harder to implement for PHP?.

Parameters

URL will be /static-text;
internal - do not allow to access index_cached_1h.php except in internal requests.
fastcgi_cache_key - variables from which the cache is constructed. Will be explained later in more details.
fastcgi_cache - the name of the cache You want to use.
fastcgi_cache_valid - “confirm that it really should expire after 1 hour”.
add_header - add info about the cache.
$upstream_cache_status - The status can be either “MISS”, “BYPASS”, “EXPIRED”, “STALE”, “UPDATING”, “REVALIDATED”, or “HIT”.
1h - a key to identify which cache was processed. Good for debugging.
always - If the always parameter is specified, the header field will be added regardless of the response code. Which means if it is not added then header sometimes can not appear.
include /snippets/fastcgi-php.conf ; - include the regular fastcgi commands like fastcgi_pass unix:/var/run/php/php7.0-fpm.sock;.

location /static-text {
	try_files $uri /index_cached_1h.php?$args;
}
location ~ \index_cached_1h.php$ {
	internal;
	fastcgi_cache_key "$scheme$request_method$host$request_uri$http_language";
	fastcgi_cache cache_1h;
	fastcgi_cache_valid 1h;
	add_header Cache-Status "$upstream_cache_status, 1h" always;
	include snippets/fastcgi-php.conf;
}

In this example cache’s file name `fastcgi_cache_key` is based on:

Protocol / scheme - $scheme. Like http, https, ftp.
Request method - $request_method. Like GET, POST, PUT.
Host domain / IP - $host. Like, example.com.
URI - $request_uri.
‘Language’ header- $http_language. Like lv, en. This header must sent with the request manually.

So if any of these values changes then a new cache is written.

Done

Now restart with sudo systemctl restart nginx.service.

Test

In the /static-text end-point add a 5 second delay.
Open the browser.
Open Dev tool’s network tab so we could see the page’s response.
Go to /static-text.
There is a 5 second delay and the response contains a new header ‘Cache-Status’ with a value “MISS, 1h”;
Refresh.
The response is instant and ‘Cache-Status’ header now is ‘HIT, 1h’.

Use the 5 minute auth cache for a user dependant content that can be 5 minutes old

Like FAQ that depends on the user that has been logged in. Like there could be different questions for a business and a personal account.

Duplicate index.php to index_cached_5m_auth.php. To understand why this is necessary read Why conditional requests are harder to implement for PHP?.

Parameters

URL will be /faq;
Here we use the same principles - define which cache to use, for how long, and add a status header.

The main differences from the example above:

The authorization is provided with one extra header cid ($http_cid) which is a unique ID that works the same as a session id or a JWT token. This header must be sent with the request manually just like the ‘Language’ header ($http_language).

Here’s an example how to do that:

Set the cid cookie after the user has been logged in. Set it to 5 minutes.

setcookie('cid', hash('sha256',mt_rand()),time()+60*60*24*7, '/', $_SERVER['HTTP_HOST'], false, false);

Attach the cookie’s value to the requeast as cid header.
Remove this cookie in the logout method.

Hints:

If the cid cookie value can not be read and sent then try to set the ‘http_only’ (I guess the last param) value to false because otherwise cookie is not accessible to Javascript.
It could be necessary to add the cid header in the CORS file to the list of allowed headers.

This header is used at the end of the fastcgi_cache_key with the $http_cid variable where the pattern is $http_HEADER_KEY.

location /faq {
	try_files $uri /index_cached_5m_auth.php?$args;
}
location ~ \index_cached_5m_auth.php$ {
	internal;
	fastcgi_cache_key "$scheme$request_method$host$request_uri$http_language$http_cid";
	fastcgi_cache cache_5m_auth;
	fastcgi_cache_valid 5m;
	add_header Cache-Status "$upstream_cache_status, 5m_auth" always;
	include snippets/fastcgi-php.conf;
}

Test

In the /faq end-point add a 5 second delay.
Open the browser.
Open Dev tool’s network tab so we could see the page’s response.
Go to /faq.
There is a 5 second delay and the response contains a new header ‘Cache-Status’ with a value “MISS, 5m_auth”;
Refresh.
The response is instant and ‘Cache-Status’ header now is ‘HIT, 5m_auth’.

Additional note

If you don’t want the cache to be used if the authorization ID cid have not been sent then you just need to add a condition that changes blocks according to the $http_cid value.

Example

location /faq {
	set $index_file 'index.php';
	if ($is_auth = true) {
		set $index_file 'index_cached_5m_auth.php';
	}
	try_files $uri /$index_file?$args;
}

nginx

Janis Rullis NGINX configs and notes

/ nginx / docs

PHP caching / NOT REVERSE PROXY CACHING

What is a reverse proxy?

Difference between reverse proxy caching and PHP caching

Reverse proxy cache

PHP caching

Setup the cache

Define those caches in the nginx.conf

Explanation

Tell NGINX that we want to control cache by our own

Define allowed request methods that can be cached

Use the 1 hour unauth cache for a static content like text

See a working example.

Parameters

In this example cache’s file name `fastcgi_cache_key` is based on:

Done

Test

Use the 5 minute auth cache for a user dependant content that can be 5 minutes old

Parameters

The main differences from the example above:

Test

Additional note

Example

Resources

nginx

Janis Rullis NGINX configs and notes

/ nginx / docs

PHP caching / NOT REVERSE PROXY CACHING

What is a reverse proxy?

Difference between reverse proxy caching and PHP caching

Reverse proxy cache

PHP caching

Setup the cache

Define those caches in the nginx.conf

Explanation

Tell NGINX that we want to control cache by our own

Define allowed request methods that can be cached

Use the 1 hour unauth cache for a static content like text

See a working example.

Parameters

In this example cache’s file name fastcgi_cache_key is based on:

Done

Test

Use the 5 minute auth cache for a user dependant content that can be 5 minutes old

Parameters

The main differences from the example above:

Test

Additional note

Example

Resources

In this example cache’s file name `fastcgi_cache_key` is based on: