White Screen of Death for unknown reason but fixes after rebooting the server

Question

The problem we are experiencing is very new to us. We did not experience this ever before with our website or with our web server (in last 8 years). Just recently for last 2 week we have this issue and it happened over 3 times.

Problem Description

Our site is experiencing "White Screen of Death". We do not see any error. Please see screenshot for better understanding. its just that. The site just tries to load but cannot.

Findings : what we have done to fix this

We can fix it (temporarily) if we reboot the server (restarting the whole virtual machine).

But this is not a viable solution . As we have other Wordpress and non-Wordpress websites in that server which does not have that issue. And rebooting the server means all sites in the server are down for 5-10 minutes. After rebooting the server site comes back and works fine as usual.

But This problem occurred at least 3 times since last week. We cannot replicate the error by clicking on any page. There is no particular time of the day when this happens.

Further information

The only significant change we can think of is upgrading the PHP version for the site from 5.3 to 7.2 in our web server. FYI we have upgraded the PHP version last month. And for approximately 3 weeks we have not seen this or any other issue. The wordpress version of the site is 4.9.1

Webserver - Apache

Database - My SQL 5.1.7

We have plenty free disk space in the server

We have tried to look in to the error log at the time of the problem . but we could not find any thing relevant. This is the error we could see on error log. Although I didn't think it was the issue but I have corrected the SQL query mentioned in the error log. But we have faced the same issue again today.

I can see the following log files from my cpanel

Webserver error log Web server ssl error log

web server transfer log

webserver ssl transfer log

[Tue Apr 23 13:48:35 2019] [error] [client 101.180.145.79] FastCGI: server "/var/run/psychicf-remi-safe-php72.fcgi" stderr: PHP message: WordPress database error You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'ORDER BY number DESC' at line 1 for query SELECT * FROM  view_site_numbers WHERE campaign_id = "7" AND `use` = "PPC" LIMIT 2 ORDER BY number DESC made by require('wp-blog-header.php'), require_once('wp-includes/template-loader.php'), include('/themes/psychicFuture/css/content-all-horoscopes.php'), get_header, locate_template, load_template, require_once('/themes/psychicFuture/header.php'), do_shortcode, preg_replace_callback, do_shortcode_tag, get_prs_number_register, referer: https://thehoroscopejunkie.ca/weekly_horoscopes.html

PHP Compatibility checker plugin showing the following error I do not know where to look at. Can you please advice ?

Answer 1

I don't think this can provide a solution but hopefully I can help you troubleshoot a little.

Firstly, let's go over debugging:

Debugging

You're saying "white screen of death", but the screenshot you provided looks more like it's hanging while trying to load the page. Typically, the WSOD appears as exactly that - a completely blank page. Your screenshot shows the default "New Tab" view and a loading spinner, suggesting that the server is not responding.

If you leave this page "loading" for a bit of time (several minutes at least), do you get any kind of error? Usually, Chrome will eventually kick in with a message like "Too many redirects" or something similar when it finally gives up or does it actually finally fail with a white screen?

wp-admin and White Screen

If it is a white screen, what do you get when trying to go to /wp-admin/? This is important, because WordPress will surface some debugging-related information if there is a problem in your installation's database setup when you access /wp-admin/ that would otherwise not appear on the front-end.

WordPress debug log

WordPress also includes internal debugging that is disabled by default. In your question, you note that you checked the error logs, but didn't specify which ones. It could be helpful to do the following:

• Add these lines to wp-config.php:

define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true );

This will enable debug logging to the file /wp-content/debug.log. Try loading your site again and waiting until the load fails (server timeout, too many redirects, etc). Check the log to see if you find any errors

The SQL Error

While likely not the cause of your issues, the SQL error can be easily handled. Your custom query should have the LIMIT statement after the ORDER BY clause:

SELECT * FROM  view_site_numbers WHERE campaign_id = "7" AND `use` = "PPC"  ORDER BY number DESC LIMIT 2

Further investigation

As others have noted, it may be worth looking at stackoverflow.com for more help, as the issue definitely "feels" server-related. You said you recently upgraded your PHP version - it might not hurt to see if you can downgrade and see if the issue persists, however, I can't think of anything off the top of my head that might cause an issue like this (if it is infinite loading and not a direct white screen).

Also, given that it only happens intermittently, makes me think it's less to do with the application code than something going on with the server itself. If you have access to access logs you could check for DDOS attempts. You should also check your processes to see if anything is leaking and eating more and more memory without being properly stopped, or just running forever and eating away at your CPU.

Good luck!

Answer 2

I'd recommend updating WP, and all themes and plugins to current versions. And you might check the version of PHP actually being used. (create a template and replace the 'loop' with a phpinfo() function, or look via your hosting cpanel).

Perhaps the 'fastcgi' option is not good for your site, so try going back to 'regular' PHP 7.x.

The error log should give you more info, but you mentioned already looking there. Your hosting support might be helpful. (If you have hosting for your site; although it appears you are self-hosted.)