Suddenly error 503 only on admin-panel

@dotch This is unusual, something that warrants checking the PHP error log. Are you by any chance using any CDN, e.g., Cloudflare? Is it possible to share the website link so that I can take a look? Have there been any recent changes made to the website, such as installing/updating a plugin, theme, or changing any plugin settings, etc.?

I had the same issue with two sites that I manage. Tried changing php version to 8.2 and 8.3 but that did not fix the issue. I had to disable the plugin at the hosting file manager level and the site returned to normal.

Can anybody share the PHP error log via https://pastebin.com/ so that we can check? It should be available in cPanel or the hosting dashboard, or you can ask your hosting provider about it.

Also, which hosting service are you using? It would also be helpful if you could share the server information, which can be found in this screenshot: https://prnt.sc/D8D6wWFpRsA6

As of about a week or so, I’m getting Error 503 on all my pages, not just my admin page. Disabling WP Optimize fixes the issue. No clue what the issue is since I’ve been using it for a long time and it didn’t even start with an update. I’m curious if it’s an issue with LiteSpeed servers.

Server architecture Linux 2.6.32-954.3.5.lve1.4.90.el6.x86_64 x86_64
Web server LiteSpeed
PHP version 8.1.26 (Supports 64bit values)
PHP SAPI litespeed
PHP max input variables 2000
PHP time limit 1500
PHP memory limit 1024M
Max input time 1500
Upload max filesize 1024M
PHP post max size 1024M
cURL version 7.87.0 OpenSSL/1.1.1w
Is SUHOSIN installed? No
Is the Imagick library available? Yes
Are pretty permalinks supported? Yes
.htaccess rules Custom rules have been added to your .htaccess file.
Current time 2023-12-24T21:56:44+00:00
Current UTC time Sunday, 24-Dec-23 21:56:44 UTC
Current Server time 2023-12-24T16:56:43-05:00

These are the only relevant logged errors.

[24-Dec-2023 21:55:38 UTC] Cron reschedule event error for hook: wpo_purge_old_cache, Error code: invalid_schedule, Error message: Event schedule does not exist., Data: {"schedule":"wpo_purge_old_cache","args":[],"interval":86400}
[24-Dec-2023 21:57:48 UTC] Cron reschedule event error for hook: wpo_reset_webp_conversion_test_result, Error code: invalid_schedule, Error message: Event schedule does not exist., Data: {"schedule":"wpo_daily","args":[],"interval":86400}

My web host said something is causing the CPU to hit 100% usage and it therefore throws the 503. Since disabling WP Optimize resolves the issue, it sounds like the plugin is working overtime because of an issue and it’s crashing the site due to the CPU overload.

@stathious @mhoerner @dotch Can you also confirm which server you’re using, specifically whether it’s a LiteSpeed server or not?

I’m on shared hosting at one of the big hosts these days:

Server architecture	Linux 2.6.32-954.3.5.lve1.4.91.el6.x86_64 x86_64
Web server	LiteSpeed
PHP version	8.1.26 (Supports 64bit values)
PHP SAPI	litespeed
PHP max input variables	2000
PHP time limit	1500
PHP memory limit	1024M
Max input time	1500
Upload max filesize	1024M
PHP post max size	1024M

The only change I made about 5 week ago is, that I installed the plugin ‘Independent Analytics’ . But the 503 error started much later, as far as I know.

I think there are no relevant error messages.

All my plugins are set to auto-update. The ones that seem to have been updated recently are:

independent-analytics / Nov 19
*wp-optimize / Nov 22
complianz-gdpr / Dec 13
google-sitemap-generator / Dec 19
limit-login-attempts-reloaded / Dec 20

• This reply was modified 11 months ago by James Huff.
• This reply was modified 11 months ago by dotch.
• This reply was modified 11 months ago by dotch.

@kowsar89 I know WordPress dashboard gives an error message that WP Optimize may conflict with Litespeed, but I disabled the caching features of WPO. I’m not sure if that’s part of/cause of the 503 issue or not.

@kowsar89

I confirm that the shared hosting service I use for all my installations/clients is a LiteSpeed server but LiteSpeed caching plugin is disabled because I normally use WP-Optimize for caching.

• This reply was modified 11 months ago by stathious.

@stathious @mhoerner @dotch @amsgator Are you guys, by any chance, using Namecheap hosting? Additionally, are you using the “LiteSpeed Cache” plugin in conjunction with WP-Optimize? Just trying to connect a few dots, this information will help. Thanks

@kowsar89 mine is with Namecheap. The issue just recently started within the last week or so. I haven’t had any issues up until recently. I am also using the Litespeed plugin for caching and I have disable caching with WPO. I mostly use WPO for its database cleanup features.

also have problem also using namecheap but i dont have litespeed plugin

@kowsar89 I also use Namecheap webhosting but LiteSpeed is disabled globally from cPanel for all my installations. Instead I only use WP-Optimize plugin for caching. Hope this helps…

I’m also using Namecheap shared hosting, no Litespeed.

@kowsar89 I can confirm that we are using namecheap for this particular installation and had the Litespeed plugin disabled as I prefer WPO.

Based on the collective data I’ve gathered so far, I’ve compiled the following key points:

1. There have been several reports of this issue, all occurring within the same timeframe.
2. Notably, all these reports are originating from Namecheap users, and it’s worth noting that Namecheap utilizes the LiteSpeed server internally.
3. I conducted a test of our plugin on another hosting platform that also uses LiteSpeed servers, and it functioned perfectly there. This suggests that the issue might not be related to the LiteSpeed server itself.
4. Our plugin hasn’t undergone any recent updates; the last one was months ago. So, recent changes in the plugin’s codebase can be ruled out as a potential cause.
5. There’s one report indicating that CPU usage spikes to 100% during the error occurrence. In my experience, certain shared hosting providers impose Disk I/O limits on their users. Consequently, when a process involving a high volume of file read/write operations (such as cache preloading) is initiated, the CPU can quickly hit its limit due to these restrictions. I didn’t expect Namecheap to be one of these providers.

Considering this information, I have reason to suspect that the issue might be originating from Namecheap, possibly due to alterations in their server configuration or additional resource usage restrictions imposed on their shared hosting users – I don’t know. While I can’t confirm whether all Namecheap users are affected, it is evident that all users reporting this issue are using Namecheap.

I am interested in hearing what Namecheap hosting has to say about this matter, perhaps you guys can reach out to their support? If the root cause lies within Namecheap, I hope they will address it promptly. On the other hand, if Namecheap believes the issue is related to WP-Optimize (despite the fact that millions of users use WP-Optimize without any issues), I believe they could provide more specific information about this, such as which part of WP-Optimize’s codebase is triggering the issue. As a hosting provider, they should be well-equipped to provide such information.