Cluster Health Policy
Defines a health policy used to evaluate the health of the cluster or of a cluster node.
Properties
| Name | Type | Required |
|---|---|---|
ConsiderWarningAsError |
boolean | No |
MaxPercentUnhealthyNodes |
integer | No |
MaxPercentUnhealthyApplications |
integer | No |
ApplicationTypeHealthPolicyMap |
array of ApplicationTypeHealthPolicyMapItem | No |
NodeTypeHealthPolicyMap |
array of NodeTypeHealthPolicyMapItem | No |
ConsiderWarningAsError
Type: boolean
Required: No
Default: false
Indicates whether warnings are treated with the same severity as errors.
MaxPercentUnhealthyNodes
Type: integer
Required: No
Default: 0
The maximum allowed percentage of unhealthy nodes before reporting an error. For example, to allow 10% of nodes to be unhealthy, this value would be 10.
The percentage represents the maximum tolerated percentage of nodes that can be unhealthy before the cluster is considered in error. If the percentage is respected but there is at least one unhealthy node, the health is evaluated as Warning. The percentage is calculated by dividing the number of unhealthy nodes over the total number of nodes in the cluster. The computation rounds up to tolerate one failure on small numbers of nodes. Default percentage is zero.
In large clusters, some nodes will always be down or out for repairs, so this percentage should be configured to tolerate that.
MaxPercentUnhealthyApplications
Type: integer
Required: No
Default: 0
The maximum allowed percentage of unhealthy applications before reporting an error. For example, to allow 10% of applications to be unhealthy, this value would be 10.
The percentage represents the maximum tolerated percentage of applications that can be unhealthy before the cluster is considered in error. If the percentage is respected but there is at least one unhealthy application, the health is evaluated as Warning. This is calculated by dividing the number of unhealthy applications over the total number of application instances in the cluster, excluding applications of application types that are included in the ApplicationTypeHealthPolicyMap. The computation rounds up to tolerate one failure on small numbers of applications. Default percentage is zero.
ApplicationTypeHealthPolicyMap
Type: array of ApplicationTypeHealthPolicyMapItem
Required: No
Defines a map with max percentage unhealthy applications for specific application types.
Each entry specifies as key the application type name and as value an integer that represents the MaxPercentUnhealthyApplications percentage used to evaluate the applications of the specified application type.
The application type health policy map can be used during cluster health evaluation to describe special application types. The application types included in the map are evaluated against the percentage specified in the map, and not with the global MaxPercentUnhealthyApplications defined in the cluster health policy. The applications of application types specified in the map are not counted against the global pool of applications. For example, if some applications of a type are critical, the cluster administrator can add an entry to the map for that application type and assign it a value of 0% (that is, do not tolerate any failures). All other applications can be evaluated with MaxPercentUnhealthyApplications set to 20% to tolerate some failures out of the thousands of application instances. The application type health policy map is used only if the cluster manifest enables application type health evaluation using the configuration entry for HealthManager/EnableApplicationTypeHealthEvaluation.
NodeTypeHealthPolicyMap
Type: array of NodeTypeHealthPolicyMapItem
Required: No
Defines a map with max percentage unhealthy nodes for specific node types.
Each entry specifies as key the node type name and as value an integer that represents the MaxPercentUnhealthyNodes percentage used to evaluate the nodes of the specified node type.
The node type health policy map can be used during cluster health evaluation to describe special node types. They are evaluated against the percentages associated with their node type name in the map. Setting this has no impact on the global pool of nodes used for MaxPercentUnhealthyNodes. The node type health policy map is used only if the cluster manifest enables node type health evaluation using the configuration entry for HealthManager/EnableNodeTypeHealthEvaluation.
For example, given a cluster with many nodes of different types, with important work hosted on node type "SpecialNodeType" that should not tolerate any nodes down. You can specify global MaxPercentUnhealthyNodes to 20% to tolerate some failures for all nodes, but for the node type "SpecialNodeType", set the MaxPercentUnhealthyNodes to 0 by setting the value in the key value pair in NodeTypeHealthPolicyMapItem. The key is the node type name. This way, as long as no nodes of type "SpecialNodeType" are in Error state, even if some of the many nodes in the global pool are in Error state, but below the global unhealthy percentage, the cluster would be evaluated to Warning. A Warning health state does not impact cluster upgrade or other monitoring triggered by Error health state. But even one node of type SpecialNodeType in Error would make cluster unhealthy (in Error rather than Warning/Ok), which triggers rollback or pauses the cluster upgrade, depending on the upgrade configuration.
Conversely, setting the global MaxPercentUnhealthyNodes to 0, and setting SpecialNodeType's max percent unhealthy nodes to 100, with one node of type SpecialNodeType in Error state would still put the cluster in an Error state, since the global restriction is more strict in this case.