Preloader via cron job issue

Are you running the WP Cron with PHP execution instead of wget?

WP Cron is disabled, and I’m running cron from my server. The issue is that Cloudflare is caching both your purge and preloader URLs. They work the first time, then they get cached, and won’t work again until the cache clears.

These are the URLs I’m using – both are getting cached by Cloudflare:

https://[domain]?swcfpc=1&swcfpc-purge-all=1&swcfpc-sec-key=[key]
https://[domain]?swcfpc=1&swcfpc-preloader=1&swcfpc-sec-key=[key]

• This reply was modified 2 years, 10 months ago by PurpleNurple.
• This reply was modified 2 years, 10 months ago by PurpleNurple.

I’m running cron from my server

– Yes but when you do that you can wither do it via wget or via php. Example: https://www.looklinux.com/how-to-execute-php-script-in-crontab-in-linux/#Configure_Corn_Task

The issue is that Cloudflare is caching both your purge and preloader URLs

– I don’t understand. From the example log you have given above you are first running a purge request swcfpc-purge-all=1 and then the preloader request swcfpc-preloader=1

Yes, I am running WP Cron via PHP. It’s working fine.

The two commands in my last post are not from a log. They are the commands shown within your plugin for purging and preloading, respectively. They would not be run at the same time. Both the purge and preloader pages are being cached by Cloudflare, because you are not setting the proper headers for those pages.

If the request is sent via CRON job then the cache-control headers are supposed to be no-cache

Cache control headers are best handled at the server (reply), not the client (request). It would also seem to be fairly trivial to modify your plugin code to handle the reply headers. That said, I went ahead and added cache headers to my cron job, butit appears that Cloudflare is ignoring cache headers in the request.

My new cron job uses the following code:
curl -sv -H "cache-control: no-store, no-cache, max-age=0" -H "pragma: no-cache" "https://[domain]?swcfpc=1&swcfpc-preloader=1&swcfpc-sec-key=[key]"

Cron request headers:

GET /?swcfpc=1&swcfpc-preloader=1&swcfpc-sec-key=[key] HTTP/1.1
User-Agent: curl/7.29.0
Host: [domain]
Accept: */*
cache-control: no-store, no-cache, max-age=0
pragma: no-cache

First reply headers (after purging Cloudflare cache):

HTTP/1.1 200 OK
Date: Thu, 05 May 2022 18:18:05 GMT
Content-Type: text/html; charset=UTF-8
Transfer-Encoding: chunked
Connection: keep-alive
x-powered-by: PHP/7.4.29
vary: Accept-Encoding
alt-svc: h3=":443"; ma=86400, h3-29=":443"; ma=86400
x-turbo-charged-by: LiteSpeed
CF-Cache-Status: EXPIRED
Last-Modified: Thu, 05 May 2022 17:19:04 GMT
Expect-CT: max-age=604800, report-uri="https://report-uri.cloudflare.com/cdn-cgi/beacon/expect-ct"
Report-To: [...]
NEL: {"success_fraction":0,"report_to":"cf-nel","max_age":604800}
Server: cloudflare
CF-RAY: [...]

Second reply headers:

HTTP/1.1 200 OK
Date: Thu, 05 May 2022 18:19:01 GMT
Content-Type: text/html; charset=UTF-8
Transfer-Encoding: chunked
Connection: keep-alive
x-powered-by: PHP/7.4.29
vary: Accept-Encoding
alt-svc: h3=":443"; ma=86400, h3-29=":443"; ma=86400
x-turbo-charged-by: LiteSpeed
CF-Cache-Status: HIT
Age: 56
Last-Modified: Thu, 05 May 2022 18:18:05 GMT
Expect-CT: max-age=604800, report-uri="https://report-uri.cloudflare.com/cdn-cgi/beacon/expect-ct"
Report-To: [...]
NEL: {"success_fraction":0,"report_to":"cf-nel","max_age":604800}
Server: cloudflare
CF-RAY: [...]

Cache control headers are best handled at the server (reply), not the client (request). It would also seem to be fairly trivial to modify your plugin code to handle the reply headers. That said, I went ahead and added cache headers to my cron job, butit appears that Cloudflare is ignoring cache headers in the request.

– The plugin set the proper cache control header on the Response and not Request. Here are a few snapshot from the plugin code:

View post on imgur.com

There is also a .htaccess rule and nginx rule based on what server you are using to set cache control header for the /wp-cron.php endpoint:

View post on imgur.com

View post on imgur.com

Please check if you have added the required rules in your htaccess or nginx.conf file.

Thank you for working with me on this issue. I do very much appreciate your time.

I’m not having issues with wp-cron.php. As I mentioned before I’m running it via PHP not via URL, so it’s not affected by caching. Also, since I’m running LiteSpeed (see the reply headers in my last comment), which is compatible with Apache, the plugin already adds the proper .htaccess rules. Cron is not the issue.

The plugin is adding proper cache headers in most cases, but it is not adding them for the preloader and purge-all pages. If you look at the headers in my previous message, you’ll see that this is true.

I spent about an hour digging into the plugin’s code, and I found the bug. The plugin is using the nocache_headers filter hook to add headers, but for these two pages, die() is being called before this hook executes. One way to fix this is to add the following code above die() within the cronjob_preloader() and cronjob_purge_cache() functions:

if ( ! headers_sent() ) {
    nocache_headers();
}

Hi,
I have added the fix that you have mentioned. It will be added in the upcoming release of the plugin. In the mean time you can try replacing the plugin code with the content of this ZIP file and check if this resolves your issue.