Add description of metrics exported by Machine Config Daemon

_topic_map.yml

@@ -861,6 +861,8 @@ Topics:
 #    File: nodes-nodes-problem-detector
   - Name: Viewing node audit logs
     File: nodes-nodes-audit-log
+  - Name: Machine Config Daemon metrics
+    File: nodes-nodes-machine-config-daemon-metrics
 - Name: Working with containers
   Dir: containers
   Topics:

modules/machine-config-daemon-metrics.adoc

@@ -0,0 +1,77 @@
+// Module included in the following assemblies:
+//
+// * nodes/nodes/nodes-nodes-machine-config-daemon-metrics.adoc
+
+[id="machine-config-daemon-metrics_{context}"]
+= Machine Config Daemon metrics
+
+Beginning {product-title} 4.3, the Machine Config Daemon provides a set of metrics. These metrics can be accessed using the Prometheus Cluster Monitoring stack.
+
+The following table describes this set of metrics. Note that:
+
+* Metrics marked with `*` in the `Name` and `Description` columns represent serious errors that might cause performance problems. Such problems might prevent updates and upgrades from proceeding.
+* While some entries contain commands for getting specific logs, the most comprehensive set of logs is available using the `oc adm must-gather` command.
+
+[cols="1,1,2,2", options="header"]
+.MCO metrics
+|===
+|Name
+|Format
+|Description
+|Notes
+
+|mcd_host_os_and_version
+|[]string{"os", "version"}
+|Shows the OS that MCD is running on, such as RHCOS or RHEL. In case of RHCOS, the version is provided.
+|
+
+|ssh_accessed
+|counter
+|Shows the number of successful SSH authentications into the node.
+|The non-zero value shows that someone might have made manual changes to the node. Such changes might cause irreconcilable errors due to the differences between the state on the disk and the state defined in the machine configuration.
+
+|mcd_drain*
+|{"drain_time", "err"}
+|Logs errors received during failed drain. *
+|While drains might need multiple tries to succeed, terminal failed drains prevent updates from proceeding. The `drain_time` metric, which shows how much time the drain took, might help with troubleshooting. For further investigation, see the logs by running:
+
+`$ oc logs -f -n openshift-machine-config-operator machine-config-daemon-<hash> -c machine-config-daemon`
+
+|mcd_pivot_err*
+|[]string{"pivot_target", "err"}
+|Logs errors encountered during pivot. *
+|Pivot errors might prevent OS upgrades from proceeding. For further investigation, see the logs by running these commands:
+
+`$ oc logs -f -n openshift-machine-config-operator machine-config-daemon-<hash> -c machine-config-daemon`
+
+`$ journalctl -u pivot.service`
+
+|mcd_state
+|[]string{"state", "reason"}
+|State of Machine Config Daemon for the indicated node. Possible states are "Done", "Working", and "Degraded". In case of "Degraded", the reason is included.
+|For further investigation, see the logs by running:
+
+`$ oc logs -f -n openshift-machine-config-operator machine-config-daemon-<hash> -c machine-config-daemon`
+
+|mcd_kubelet_state*
+|[]string{"err"}
+|Logs kubelet health failures.  *
+|This is expected to be empty, with failure count of 0. If failure count exceeds 2, the error indicating threshold is exceeded. This indicates a possible issue with the health of the kubelet. For further investigation, see the logs by running:
+
+`$ journalctl -u kubelet`
+
+|mcd_reboot_err*
+|[]string{"message", "err"}
+|Logs the failed reboots and the corresponding errors. *
+|This is expected to be empty, which indicates a successful reboot. For further investigation, see the logs by running:
+
+`$ oc logs -f -n openshift-machine-config-operator machine-config-daemon-<hash> -c machine-config-daemon`
+
+|mcd_update_state
+|[]string{"config", "err"}
+|Logs success or failure of configuration updates and the corresponding errors.
+|The expected value is `rendered-master/rendered-worker-XXXX`. If the update fails, an error is present. For further investigation, see the logs by running:
+
+`$ oc logs -f -n openshift-machine-config-operator machine-config-daemon-<hash> -c machine-config-daemon`
+|===
+

nodes/nodes/nodes-nodes-machine-config-daemon-metrics.adoc

@@ -0,0 +1,13 @@
+[id="machine-config-daemon-metrics"]
+= Machine Config Daemon metrics
+include::modules/common-attributes.adoc[]
+:context: machine-config-operator
+
+The Machine Config Daemon is a part of the Machine Config Operator. It runs on every node in the cluster. Machine Config Daemon's purpose is managing configuration changes and updates on each of the nodes.
+
+include::modules/machine-config-daemon-metrics.adoc[leveloffset=+1]
+
+.Additional resources
+
+* See xref:../../monitoring/cluster-monitoring/about-cluster-monitoring.adoc[the documentation on the Prometheus Cluster Monitoring stack].
+* See link:https://github.com/openshift/must-gather[the repository of the must-gather tool].