Retrieve keys hangs: License is in grace period even though it was updated

Symptoms

• License is in grace period even though it was updated/renewed correctly on a licensing server side:

  Warning: You are currently operating within the grace period of your product license. To update your product license, select the Retrieve Keys option on the License Management page.

• While trying to retrieve/install keys at Plesk > Tools & Settings > License Management (Plesk > Tools & Settings > Server information) the page loads forever until it fails with:

  504 Gateway Timeout

• The same error may appear when trying to log into Plesk.

• After enabling debug, in /var/log/plesk/panel.log it can be seen that the license update stops on the following step:

  DEBUG [util_exec] [5af1e640d2247] Starting: sysinfo df-full, stdin:

• The following df (disk free) processes can be found:

  # ps aux | grep df
  root 6806 0.0 0.0 18356 2012 ? S 06:46 0:00 /usr/local/psa/admin/bin/sysinfo df-full
  root 7229 0.0 0.1 18356 4416 ? S 06:48 0:00 /usr/local/psa/admin/bin/sysinfo df-full
  <..>
  root 11409 0.0 0.1 18356 4424 ? S 12:55 0:00 /usr/local/psa/admin/bin/sysinfo df-full
  root 13955 0.0 0.1 18356 4420 ? S 12:57 0:00 /usr/local/psa/admin/bin/sysinfo df-full

• df -h command hangs

Cause

The "df" utility processes are hung (for example due to bug in CentOS / RedHat 7.5 in CentOS 7.5, however Ubuntu operating system might be affected too) causing Plesk services to hang too.

The issue is also registered as Plesk bug PPPM-8614 which is planned to be fixed in future product updates.

Resolution

Note: it is not recommended to kill the stuck df processes.

Reboot the server to fix df command related issue. All Plesk services will work correctly when df command can be executed normally.