Forwarded to devs Nginx Caching size can be set to zero, which causes a web server configuration error

[Bitpalast]

Username: Peter Debik

TITLE

Nginx Caching size can be set to zero, which causes a web server configuration error

PRODUCT, VERSION, OPERATING SYSTEM, ARCHITECTURE

Plesk Obsidian, latest MU
CentOS 7.9

PROBLEM DESCRIPTION

It is possible to set the Nginx cache size to zero. However, that value is considered an invalid entry into the max_size configuration parameter of Nginx. As subscribers can manage this setting by themselves, they can cause issues to the system in general by setting a false value.

STEPS TO REPRODUCE

Set the cache size to zero.

ACTUAL RESULT

Webserver configuration error (e.g. in web server configurations trouble shooter)

EXPECTED RESULT

a) Zero must not be allowed as a parameter.
or
b) When set to zero, the cache should be disabled.

ANY ADDITIONAL INFORMATION

First seen in

Resolved - Template_Exception: nginx: [emerg] invalid max_size value "max_size=" in /etc/nginx/plesk.conf.d

How can this error be fixed? Details: [2020-10-11 22:53:33.670] ERR [util_exec] proc_close() failed ['/opt/psa/admin/bin/nginx-config' '-t'] with exit code [1] [2020-10-11 22:53:41.610] ERR [panel] Apache config (16024495840.16543000) generation failed: Template_Exception: nginx: [emerg]...

talk.plesk.com

and confirmed issue in our own servers.

YOUR EXPECTATIONS FROM PLESK SERVICE TEAM

Confirm bug

 

[IgorG]

Peter, the issue PPP-50663 is resolved in 18.0.31, it seems you have a too old version of Plesk, not latest MU?

 

[Bitpalast]

It's just recently occured twice in two different subscriptions on a system that was upgraded by Plesk staff and is running 18.0.31 MU #2, last updated December 1st. No other issues on that system.

 

[Bitpalast]

It just happend a third time, same system, upgraded last night to 18.0.31 MU #3.

 

[Bitpalast]

@IgorG I think we caught it. I was able to speak to the customer who caused the false configuration. He told me that he is a noob and did NOT use the Apache/Nginx settings. Instead he disabled Nginx caching in the Wordpress Toolkit. So maybe developers might want to check whether this can cause the zero setting in the Nginx caching values. I think that this is a very reasonable starting point for further analysis, because there is another issue linked with the same configuration option in Wordpress Toolkit: When you turn Nginx caching on/off there, the Apache/Nginx setting page setting is not affected by it. For example when I turn off Nginx caching in WP Toolkit, the corresponding switch on the Nginx settings is not turned off. When I toggle the switch on the Nginx settings page, the corresponding switch in WP Toolkit is not modified. So probably what developers have done is to remove Nginx caching values or setting them to "zero" when the switch is toggled in WP Toolkit, but have not actually turned Nginx caching off or removed all the corresponding settings in the Plesk panel option for it.

 

[Bitpalast]

Meanwhile the same issue has been seen here on two additional host systems.

 

[IgorG]

Looks like bug is related to upgrading case when wrong cache size value was stored in the database and the user tried to turn cache from WordPress toolkit.

Reported bug for this: PPPM-12605

 

[IgorG]

Fixed in 18.0.33: Change Log for Plesk Obsidian

If Plesk Obsidian was upgraded from Plesk Obsidian 18.0.30 and earlier, the nginx cache size equal to 0 can no longer break the nginx configuration. (PPPM-12605)