Plesk Monitoring thresholds cannot be updated: Request failed with status code 500

Symptoms

• An attempt to adjust the thresholds of Monitoring extention in Plesk > Monitoring > Settings > Thresholds takes a long time to load, fails, and shows the following error in the Plesk GUI:
  

  PLESK_ERROR: Request failed with status code 500

• The /var/log/plesk/panel.log contains the following errors:
  

  CONFIG_TEXT: 670406:656789c1a9c55 ERR [panel] Failed to update the Grafana state in turn.
  1670504:656789e2ce668 ERR [panel] Failed to update the Grafana state in turn.
  1101688:65678a03096ad ERR [extension/monitoring] /opt/psa/admin/plib/vendor/plesk/zf1/library/Zend/Controller/Plugin/Broker.php(336): Invalid controller specified (index)#0 /opt/psa/admin/plib/vendor/plesk/zf1/library/Zend/Controller/Front.php(954): Zend_Controller_Dispatcher_Standard->dispatch(Object(Zend_Controller_Request_Http), Object(Zend_Controller_Response_Http))

• Execution of the journalctl --unit=grafana-server command provides next output:
  

  CONFIG_TEXT: Nov 29 08:05:41 example.com grafana[1816]: logger=rendering t=2023-11-29T08:05:41.102926821+02:00 level=warn msg="Could not render image, no image renderer found/installed. For image rendering support please install the grafana-image-renderer plugin. Read more at https://grafana.com/docs/grafana/latest/administratio>
  Nov 29 16:28:41 example.com grafana[1816]: logger=plugin.plesk-json-backend-datasource t=2023-11-29T16:28:41.358211596+02:00 level=error msg="plugin process exited" path=/var/lib/grafana/plugins/plesk-json-backend-datasource/dist/gpx_plesk-json-backend-datasource_linux_amd64 pid=3992 error="signal: terminated"
  Nov 29 16:28:42 example.com grafana[1600176]: logger=plugin.loader t=2023-11-29T16:28:42.576189946+02:00 level=warn msg="Plugin missing module.js" pluginID=input warning="Missing module.js, If you loaded this plugin from git, make sure to compile it."
  Nov 29 16:28:42 example.com grafana[1600176]: logger=plugin.signature.validator t=2023-11-29T16:28:42.579208084+02:00 level=warn msg="Permitting unsigned plugin. This is not recommended" pluginID=plesk-json-backend-datasource

• The Grafana log /var/log/grafana/grafana.log
  contains errors:
  

  CONFIG_TEXT: logger=rendering t=2023-11-29T08:05:41.102926821+02:00 level=warn msg="Could not render image, no image renderer found/installed. For image rendering support please install the grafana-image-renderer plugin. Read more at https://grafana.com/docs/grafana/latest/administration/image_rendering/"
  logger=plugin.plesk-json-backend-datasource t=2023-11-29T16:28:41.358211596+02:00 level=error msg="plugin process exited" path=/var/lib/grafana/plugins/plesk-json-backend-datasource/dist/gpx_plesk-json-backend-datasource_linux_amd64 pid=3992 error="signal: terminated"
  logger=plugin.loader t=2023-11-29T16:28:42.576189946+02:00 level=warn msg="Plugin missing module.js" pluginID=input warning="Missing module.js, If you loaded this plugin from git, make sure to compile it."
  logger=plugin.signature.validator t=2023-11-29T16:28:42.579208084+02:00 level=warn msg="Permitting unsigned plugin. This is not recommended" pluginID=plesk-json-backend-datasource

• The database for Grafana on the side of Plesk contains a flag that states an update is still in progress:
  

  # sqlite3 /usr/local/psa/var/modules/grafana/grafana.sqlite3
  SQLite version 3.31.1 2020-01-27 19:55:54
  Enter ".help" for usage hints.
  sqlite> select * from params;
  ...
  ms_update_is_in_progress|1

Cause

This issue usually occurs when a flag remains during the installation of the Grafana extension. In cases when something interrupts a Grafana installation, the lock may remain and cause such errors.

Resolution

1. Log into your server via SSH

2. Remove the Grafana and Monitoring extensions by executing the following commands:

# plesk bin extension --uninstall grafana

# plesk bin extension --uninstall monitoring

3. Remove Grafana from the server completely by executing one of the following commands (based on the operating system):

• For Debian-based operating systems:
  

  # apt purge grafana && rm -rf /usr/share/grafana /etc/grafana /var/lib/grafana

• For RHEL-based operating systems:
  

  # yum remove grafana && rm -rf /usr/share/grafana /etc/grafana /var/lib/grafana

4. Reinstall the Grafana extension and the Plesk Monitoring extension by executig the following commands:

# plesk bin extension --install grafana

# plesk bin extension --install monitoring