Grafana is flooding with emails on Plesk: Firing Value: [no value] Labels: – alertname = DatasourceError

Symptoms

• The following is shown by Grafana:

  Firing Value: [no value] Labels: - alertname = DatasourceError - rule_uid = XxXxXxXx - rulename = Partition "/var" utilization - sourceKey = hdd_util_var Annotations: - message = The disk space is almost full! Source: /modules/grafana/service/alerting/grafana/XxXxXxXx/view Silence: /modules/grafana/service/alerting/silence/new?alertmanager=grafana&matcher=alertname%3DDatasourceError&matcher=rule_uid%XxXxXxXx&matcher=rulename%3DPartition+%22%2Fvar%22+utilization&matcher=sourceKey%3Dhdd_utilvar Dashboard: /modules/grafana/service/d/monitoringhdd Panel: /modules/grafana/service/d/monitoring_hdd?viewPanel=4

  *Firing* Value: [no value] Labels: - alertname = DatasourceError - rule_uid = XxXxXxXx - rulename = nginx memory usage - sourceKey = memory_usage__webproxy Annotations: - message = The memory usage status is critical! Source: /modules/grafana/service/alerting/grafana/XxXxXxXx/view Silence: /modules/grafana/service/alerting/silence/new?alertmanager=grafana&matcher=alertname%3DDatasourceError&matcher=rule_uid%XxXxXxXx&matcher=rulename%3Dnginx+memory+usage&matcher=sourceKey%3Dmemory_usage__webproxy Dashboard: /modules/grafana/service/d/monitoring__services Panel: /modules/grafana/service/d/monitoring__services?viewPanel=7
  The current value is .

• Plesk notifications show messages about exceeded thresholds which were not reached

• The following message can be found in /var/log/grafana/grafana.log:

  logger=plugin.manager t=2022-06-22T13:46:52.610714606+01:00 level=error msg="Could not start plugin" pluginId=grafana-simple-json-backend-datasource err="Incompatible API version with plugin. Plugin version: 1, Client versions: [2]"

  ---

  logger=ngalert uid=XxXxXxX org=1 t=2022-06-22T04:39:50.041885056+01:00 level=error msg="failed to fetch alert rule" err="database is locked"

Cause

Unsupported Grafana version is installed.

Resolution