K8S Probe

With the proliferation of custom resources and operators, especially in the case of stateful applications, the steady state is manifested as status parameters or flags within Kubernetes resources. K8s Probe addresses verification of the desired resource state by allowing users to define the Kubernetes GVR (group-version-resource) with appropriate filters (field selectors or label selectors). The experiment makes use of the Kubernetes Dynamic Client to achieve this. The probe supports the following CRUD operations:

• create: Creates Kubernetes resource based on the data provided inside the probe.k8sProbe/inputs.data field.

• delete: Deletes matching kubernetes resource via GVR and filters (field selectors/label selectors).

• present: Checks for the presence of Kubernetes resource based on GVR and filters (field selectors or label selectors).

• absent: Checks for the absence of Kubernetes resource based on GVR and filters (field selectors or label selectors).

The Kubernetes probe is fully declarative in the way they are conceived

Probe definition

You can define the probes at .spec.experiments[].spec.probe path inside the chaos engine.

kind: Workflow
apiVersion: argoproj.io/v1alpha1
spec:
  templates:
    - inputs:
        artifacts:
          - raw:
              data: |
                apiVersion: litmuschaos.io/v1alpha1
                kind: ChaosEngine
                spec:
                  experiments:
                    - spec:
                        probe:
                          ####################################
                          Probes are defined here
                          ####################################

Schema

Listed below is the probe schema for the Kubernetes probe, with properties shared across all the probes and properties unique to the Kubernetes probe.

Field	Description	Type	Range	Notes
group	Flag to hold the group of the Kubernetes resource for the k8sProbe	Optional	N/A type: string	The group contains group of the Kubernetes resource on which k8sProbe performs the specified operation.
version	Flag to hold the apiVersion of the Kubernetes resource for the k8sProbe	Mandatory	N/A type: string	The version contains apiVersion of the Kubernetes resource on which k8sProbe performs the specified operation
resource	Flag to hold the Kubernetes resource name for the k8sProbe	Mandatory	N/A type: string	The resource contains the Kubernetes resource name on which k8sProbe performs the specified operation.
namespace	Flag to hold the namespace of the Kubernetes resource for the k8sProbe	Optional	N/A type: string	The namespace contains namespace of the Kubernetes resource on which k8sProbe performs the specified operation.
fieldSelector	Flag to hold the fieldSelectors of the Kubernetes resource for the k8sProbe	Optional	N/A type: string	The fieldSelector contains fieldSelector to derived the Kubernetes resource on which k8sProbe performs the specified operation.
labelSelector	Flag to hold the labelSelectors of the Kubernetes resource for the k8sProbe	Optional	N/A type: string	The labelSelector contains labelSelector to derived the Kubernetes resource on which k8sProbe performs the specified operation.
operation	Flag to hold the operation type for the k8sProbe	Mandatory	N/A type: string	The operation contains operation which should be applied on the Kubernetes resource as part of k8sProbe. It supports four type of operation. It can be one of create, delete, present, absent.
resourceNames	Flag to hold the resourceNames of the Kubernetes resource	Optional	N/A type: string	The resourceNames contains Kubernetes resources used for many requests.

Run properties

Field	Description	Type	Range	Notes
probeTimeout	Flag to hold the timeout of the probe	Mandatory	N/A type: string	The probeTimeout represents the time limit for the probe to execute the specified check and return the expected data
attempt	Flag to hold the attempt of the probe	Mandatory	N/A type: integer	The attempt contains the number of times a check is run upon failure in the previous attempts before declaring the probe status as failed.
interval	Flag to hold the interval of the probe	Mandatory	N/A type: string	The interval contains the interval for which probes waits between subsequent retries
probePollingInterval	Flag to hold the polling interval for the probes (applicable for all modes)	Optional	N/A type: string	The probePollingInterval contains the time interval for which continuous and onchaos probe should be sleep after each iteration
initialDelaySeconds	Flag to hold the initial delay interval for the probes	Optional	N/A type: integer	The initialDelaySeconds represents the initial waiting time interval for the probes.
stopOnFailure	Flags to hold the stop or continue the experiment on probe failure	Optional	N/A type: boolean	The stopOnFailure can be set to true/false to stop or continue the experiment execution after probe fails

Definition

probe:
  - name: "check-app-status"
    type: "k8sProbe"
    k8sProbe/inputs:
      group: ""
      version: "v1"
      resource: "pods"
      namespace: "default"
      fieldSelector: "status.phase=Running"
      labelSelector: "app=nginx"
      operation: "present" # it can be present, absent, create, delete
    mode: "EOT"
    runProperties:
      probeTimeout: 5s
      interval: 2s
      attempt: 1

Create operation

It creates the Kubernetes resources based on the data specified inside in the probe.k8sProbe/inputs.data field.

Use the following example to tune this:

# create the given resource provided inside data field <a href="#create-the-given-resource-provided-inside-data-field" id="create-the-given-resource-provided-inside-data-field"></a>
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  appinfo:
    appns: "default"
    applabel: "app=nginx"
    appkind: "deployment"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: pod-delete
    spec:
      probe:
      - name: "create-percona-pvc"
        type: "k8sProbe"
        k8sProbe/inputs:
          # group of the resource
          group: ""
          # version of the resource
          version: "v1"
          # name of the resource
          resource: "persistentvolumeclaims"
          # namespace where the instance of resource should be created
          namespace: "default"
          # type of operation
          # supports: create, delete, present, absent
          operation: "create"
          # contains manifest, which can be used to create the resource
          data: |
            kind: PersistentVolumeClaim
            apiVersion: v1
            metadata:
              name: percona-mysql-claim
              labels:
                target: percona
            spec:
              storageClassName: standard
              accessModes:
              - ReadWriteOnce
              resources:
                requests:
                  storage: 100Mi
        mode: "SOT"
        runProperties:
          probeTimeout: 5s
          interval: 2s
          attempt: 1

Delete operation

It deletes matching Kubernetes resources via GVR and filters (field selectors or label selectors) provided at probe.k8sProbe/inputs.

Use the following example to tune this:

# delete the resource matched with the given inputs <a href="#delete-the-resource-matched-with-the-given-inputs" id="delete-the-resource-matched-with-the-given-inputs"></a>
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  appinfo:
    appns: "default"
    applabel: "app=nginx"
    appkind: "deployment"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: pod-delete
    spec:
      probe:
      - name: "delete-percona-pvc"
        type: "k8sProbe"
        k8sProbe/inputs:
          # group of the resource
          group: ""
          # version of the resource
          version: "v1"
          # name of the resource
          resource: "persistentvolumeclaims"
          # namespace of the instance, which needs to be deleted
          namespace: "default"
          # labels selectors for the k8s resource, which needs to be deleted
          labelSelector: "openebs.io/target-affinity=percona"
          # fieldselector for the k8s resource, which needs to be deleted
          fieldSelector: ""
          # type of operation
          # supports: create, delete, present, absent
          operation: "delete"
        mode: "EOT"
        runProperties:
          probeTimeout: 5s
          interval: 2s
          attempt: 1

Present operation

It checks for the presence of Kubernetes resources based on GVR and filters (field selectors or labelselectors) provided at probe.k8sProbe/inputs.

Use the following example to tune this:

# verify the existence of the resource matched with the given inputs inside cluster <a href="#verify-the-existence-of-the-resource-matched-with-the-given-inputs-inside-cluster" id="verify-the-existence-of-the-resource-matched-with-the-given-inputs-inside-cluster"></a>
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  appinfo:
    appns: "default"
    applabel: "app=nginx"
    appkind: "deployment"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: pod-delete
    spec:
      probe:
      - name: "check-percona-pvc-presence"
        type: "k8sProbe"
        k8sProbe/inputs:
          # group of the resource
          group: ""
          # version of the resource
          version: "v1"
          # name of the resource
          resource: "persistentvolumeclaims"
          # namespace where the instance of resource
          namespace: "default"
          # labels selectors for the k8s resource
          labelSelector: "openebs.io/target-affinity=percona"
          # fieldselector for the k8s resource
          fieldSelector: ""
          # type of operation
          # supports: create, delete, present, absent
          operation: "present"
        mode: "SOT"
        runProperties:
          probeTimeout: 5s
          interval: 2s
          attempt: 1

Absent operation

It checks for the absence of Kubernetes resources based on GVR and filters (field selectors or labelselectors) provided at probe.k8sProbe/inputs.

Use the following example to tune this:

# verify that the no resource should be present in cluster with the given inputs <a href="#verify-that-the-no-resource-should-be-present-in-cluster-with-the-given-inputs" id="verify-that-the-no-resource-should-be-present-in-cluster-with-the-given-inputs"></a>
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  appinfo:
    appns: "default"
    applabel: "app=nginx"
    appkind: "deployment"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: pod-delete
    spec:
      probe:
      - name: "check-percona-pvc-absence"
        type: "k8sProbe"
        k8sProbe/inputs:
          # group of the resource
          group: ""
          # version of the resource
          version: "v1"
          # name of the resource
          resource: "persistentvolumeclaims"
          # namespace where the instance of resource
          namespace: "default"
          # labels selectors for the k8s resource
          labelSelector: "openebs.io/target-affinity=percona"
          # fieldselector for the k8s resource
          fieldSelector: ""
          # type of operation
          # supports: create, delete, present, absent
          operation: "absent"
        mode: "EOT"
        runProperties:
          probeTimeout: 5s
          interval: 2s
          attempt: 1