Plesk Error reading data from fastcgi server generally happens as a result of corrupted WordPress plugins.

Here at Ibmi Media, as part of our Server Management Services, we regularly help our Customers to perform related Plesk queries.

In this context, we shall look into methods to fix this Plesk error.

Nature of Plesk: Error reading data from fastcgi server 

Recently, one of our customers came across this error on at least 3 of the domains on his server. The error message is like this:

Connection reset by peer: mod_fcgid: error reading data from FastCGI server

The major symptom of this error includes:

1. WordPress is installed on the Plesk server. However, login to the WordPress admin page is slow.

2. Errors in /var/www/vhosts/system/example.com/logs/error_log:

[warn] [client 203.0.113.2] (104)Connection reset by peer: mod_fcgid: error reading data from FastCGI server, referer: https://example.com/wp-admin/
[error] [client 203.0.113.2] Premature end of script headers: edit-comments.php, referer: https://example.com/wp-admin

3. Stracing Apache processes shows the following:

# for fn in `ps fax | grep -i /usr/sbin/httpd | grep -v grep | awk '{ print $1 } '` ; do strace -fF -tT -s102400 -o /tmp/strace.log -p $fn & done
# grep plugins /tmp/strace.log | grep such
32335 02:12:05 lstat("/var/www/vhosts/example.com/httpdocs/test_rp/wp-content/languages/plugins/woocommerce-en_US.mo", 0x7ffe87108a60) = -1 ENOENT (No such file or directory) <0.000015>

Corrupted WordPress plugins can be the cause of this error. In the example above, the WooCommerce plugin is the cause.

How to fix Plesk: Error reading data from fastcgi server ?

• Initially, we log in to Plesk.
• Then we deactivate one by one all plugins for the website at Domains > example.com > WordPress > Plugins until we fix it.
• Eventually, we can Re-install or delete the plugin we have identified.

On the other hand, if we find that the permissions on the file /var/www/cgi-bin/cgi_wrapper are incorrect, we can fix it via command-line.

To do so, we connect to the server via SSH.

Then we correct the permissions:

# chown root:root /var/www
# chmod 0755 /var/www
# chown -R root:root /var/www/cgi-bin
# chmod 0755 /var/www/cgi-bin
# chmod -R 0755 /var/www/cgi-bin/cgi_wrapper

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