Issue Subdomain not working

[Clericer]

Hey, im using Plesk since 4 years and im happy how easy it is to use, but i run into some issues since the beginning.
Sometimes when i change subdomains, like chaning php valius or update certificates or change the php version.
Randomly subdomains stop working (not the one i changed, most times another random subdomain).

I have no php errors or warnings, no problems in any logfiles but the subdomain is not responding anymore.
In the most cases, the last years i could resolve the issue by disableing the subdomain and reenable it, but since the latest update this is not resolving the issue allways.
Now i sometimes have to delete the subdomain. (Apache and Plesk restarting do not fix the problem, server reboot fix it in some cases)
I realy need help, dns lookup returns the same server for the primary and the subdomains, even if the subdomain is not reachable.

When the issue appears the subdoain page is loading forever and not responding, no default plesk Page and no message about domain not reachable.

Server Version: Ubuntu 18.04.2 LTS
Plesk: Plesk Obsidian 18.0.35,

I allways hoped the next Plesk update will fix this issue but it seemes to appear more often.
I'm happy about any help.

 

[elecboy]

When you ping the domain do you get the server IP? Are you using Cloudflare or a Proxy?

 

[Kaspar]

Do you have the 'Apache graceful restart' option enabled?


I am not sure if this is the cause of your issue (or whether it will solve your issue).

 

[Clericer]

@elecboy Ping works, and all other subdomains as well. Only the page is not showing.
I do not use a proxy, no reverse nginx or some like this.

@Rasp Thank you this is a great tip. Apache graceful restart is not activated, do i have to?

 

[Kaspar]

@Rasp Thank you this is a great tip. Apache graceful restart is not activated, do i have to?

I would advise to do so. I am not sure if it will solve your issue though.

 

[multi007]

I would advise to do so. I am not sure if it will solve your issue though.

Make a restart, database, check htaccess

 

[Clericer]

Hey, guys.
Thank you for the many answers and support.
But it occured again. It seems that this is most times the same subdomain. But still without any usefull logging information.
I fixed all PHP bugs i could find on the subdomain, and activated Apache graceful.
But this morning the subdomain wasn't reachable again, the browser loading icon is spinning forever.

I activated and deactivated the domain, still no luck.
I renewed the letsencrypt certificita still not luck.
I deleted the subdomain and recreated it, and now its working again.

It is driving me crazy our customers are mad about it and me too.
How is it possible that a subdomain stops beeing reachable without any reason,
DNS is correct, Certificat is active and valid, and the subdomain is in plesk and active, and nobody did any changes on the server since 2 Weeks.
All other subdomains are working normal.
I realy hope somebody has any idea, how to start a logging or get into this issue.

 

[Clericer]

Hey, guys.
Thank you for the many answers and support.
But it occured again. It seems that this is most times the same subdomain. But still without any usefull logging information.
I fixed all PHP bugs i could find on the subdomain, and activated Apache graceful.
But this morning the subdomain wasn't reachable again, the browser loading icon is spinning forever.

I activated and deactivated the domain, still no luck.
I renewed the letsencrypt certificita still not luck.
I deleted the subdomain and recreated it, and now its working again.

It is driving me crazy our customers are mad about it and me too.
How is it possible that a subdomain stops beeing reachable without any reason,
DNS is correct, Certificat is active and valid, and the subdomain is in plesk and active, and nobody did any changes on the server since 2 Weeks.
All other subdomains are working normal.
I realy hope somebody has any idea, how to start a logging or get into this issue.

I would like to attache something i found today, its a different type of Problem but maybe all of these are creating this issue.
I cant find a solution for this errors.
Apache stops rendering sometimes, its the same strange behaviour, the page stops working and when i view the sourcecode of the page it stopped rendering in the middle (anywhere) in the php code, and only the half page is submitted. When this error occures i get this 2 Error messages in plesk error.log

AH01386: Zlib error -2 deflating data ((null))
(20014)Internal error (specific information not available):
AH01075: Error dispatching request to : (passing brigade to output filters)

But this is alsow completely random, but when it occures then allways on one single page, not at all pages.

 

[Clericer]

I would like to attache something i found today, its a different type of Problem but maybe all of these are creating this issue.
I cant find a solution for this errors.
Apache stops rendering sometimes, its the same strange behaviour, the page stops working and when i view the sourcecode of the page it stopped rendering in the middle (anywhere) in the php code, and only the half page is submitted. When this error occures i get this 2 Error messages in plesk error.log

AH01386: Zlib error -2 deflating data ((null))
(20014)Internal error (specific information not available):
AH01075: Error dispatching request to : (passing brigade to output filters)

But this is alsow completely random, but when it occures then allways on one single page, not at all pages.

i Could fix the second issue by adding:

zlib.output_compression=off
output_buffering = On

to the php settings of the subdomains.

But the first initial question still exists.