Knowledge Base

Uploading large files over PHP to website on Plesk for Linux server fails: upstream prematurely closed connection while reading response header from upstream

Symptoms

Uploading large files over PHP (about 500 MB or more) to a website on a Plesk for Linux server fails with the following error in the log file /var/www/vhosts/system/example.com/logs/proxy_error_log:

[error] 13840#0: *22012496 upstream prematurely closed connection while reading response header from upstream, client: 203.0.113.2, server: example.com, request: "POST /upload-files.php HTTP/1.1", upstream: http://203.0.113.2:7080/upload-file.php", host: "example.com", referrer: "http://example.com/upload-files.php"

PHP handler is set to FastCGI application by Apache in Domains > example.com > PHP Settings.
In Domains > example.com > PHP Settings, the parameters max_input_time, post_max_size, and upload_max_filesize are set to the sufficient values.
The nginx parameters client_max_body_size, proxy_connect_timeout, proxy_send_timeout, and proxy_read_timeout are also set to the sufficient values (either in /etc/nginx/nginx.conf or in Domains > example.com > Apache & nginx Settings > Additional nginx directives).
The Apache parameters FcgidMaxRequestLen (in Domains > example.com > Apache & nginx Settings > Additional Apache directives), FcgidIOTimeout (in /etc/apache2/mods-available/fcgid.conf or /etc/httpd/conf.d/fcgid.conf) are also set to the sufficient values.
The Apache parameter FcgidBusyTimeout is not overrided in any configuration files.

Cause

The default value – 300 seconds – of the parameter FcgidBusyTimeout is used, limiting the maximum time for handling FastCGI request to 5 minutes.

Resolution

Connect to the server via SSH
Open the configuration file /etc/apache2/mods-available/fcgid.conf (on Debian or Ubuntu) or /etc/httpd/conf.d/fcgid.conf (on RHEL-based operating systems) in the text editor
Inside the section <IfModule mod_fcgid.c>, define the parameter FcgidBusyTimeout in seconds:
```
<IfModule mod_fcgid.c>
 .......... 
 FcgidBusyTimeout 1000
 .......... 
 </IfModule>
```
Restart Apache to apply changes:
- On Debian or Ubuntu:
  
  # service apache2 restart
- On RHEL-based operating systems:
  
  # service httpd restart

Note: Repeat steps 3 and 4 in case the issue persist. Alternatively, consider to change to PHP-FPM going to Domains > example.com > PHP Setting