SOLVED Intermittent internal server errors after turning on mod_http2

[par_sebastien]

Hi,

Ever since I turned on mod_http2 in EA4 we've been getting intermittent Internal Server Errors on random sites and pages.

I've tried changing from worker to event mpm but the 500s still keep coming.

The server has low load averages.

But I did spot a few "End of script output before headers" errors in the apache error_log which is probably what causes the internal server errors but what could be causing this?

/etc/redhat-release:CentOS Linux release 7.3.1611 (Core)
/usr/local/cpanel/version:11.66.0.22
/var/cpanel/envtype:standard
CPANEL=release

Apache 2.4

• config
• config-runtime
• mod_bwlimited
• mod_cgid
• mod_dav
• mod_dav_fs
• mod_dav_lock
• mod_deflate
• mod_expires
• mod_headers
• mod_http2
• mod_mpm_event
• mod_proxy
• mod_proxy_http
• mod_proxy_wstunnel
• mod_security2
• mod_ssl
• mod_suexec
• mod_suphp
• mod_unique_id
• tools

 

[cPanelMichael]

But I did spot a few "End of script output before headers" errors in the apache error_log which is probably what causes the internal server errors but what could be causing this?

Hello,

Could you let us know the full error message you see in the Apache error log when this happens?

Thank you.

 

[par_sebastien]

Hi,

Here is a full line:

[Sat Sep 16 16:16:17.369506 2017] [core:error] [pid 5601:tid 140454364382976] [client ##.###.##.###:8132] End of script output before headers: index.php, referer: http://example.com

 

[cPanelMichael]

Hello,

Could you open a support ticket using the link in my signature so we can take a closer look?

Thank you.

 

[par_sebastien]

As per my support ticket, it seems that the root cause may be the MaxRequestWorkers limit being reached.

I changed it in WHM -> Service Configuration -> Apache Configuration -> Global Configuration from 150 (default) to 250 and waiting to see if the issue resurfaces.

I should know within 24 hours.

 

[par_sebastien]

Alright this seems to have resolved the issue!