Pod Application Function Error

The Pod Application Function Error fault injects an error into a specified function of an application running within a Kubernetes pod. This fault helps assess the application's resilience to failures at the function level.

Use cases

• Simulate third-party API failure by injecting errors into wrapper functions.
• Test application behavior when core business logic functions return unexpected errors.
• Validate retry mechanisms and fallback strategies for critical service methods.

Prerequisites

• Kubernetes >= 1.12.0
• The target application pod must be running and accessible.
• The function to inject error into must be identifiable by name.
• The litmus-admin service account must be available in the target namespace.

Permissions required

Below is a sample Kubernetes role that defines the permissions required to execute the fault.

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  namespace: hce
  name: pod-application-function-error
spec:
  definition:
    scope: Cluster # Supports "Namespaced" mode too
permissions:
  - apiGroups: [""]
    resources: ["pods"]
    verbs: ["create", "delete", "get", "list", "patch", "deletecollection", "update"]
  - apiGroups: [""]
    resources: ["events"]
    verbs: ["create", "get", "list", "patch", "update"]
  - apiGroups: [""]
    resources: ["pods/log"]
    verbs: ["get", "list", "watch"]
  - apiGroups: [""]
    resources: ["deployments, statefulsets"]
    verbs: ["get", "list"]
  - apiGroups: [""]
    resources: ["replicasets, daemonsets"]
    verbs: ["get", "list"]
  - apiGroups: [""]
    resources: ["chaosEngines", "chaosExperiments", "chaosResults"]
    verbs: ["create", "delete", "get", "list", "patch", "update"]
  - apiGroups: ["batch"]
    resources: ["jobs"]
    verbs: ["create", "delete", "get", "list", "deletecollection"]

Mandatory tunables

Target Application Tunables for Function Error Injection

Tunable	Description	Notes
NAME	Name of the target application where the function is defined.	For example: my-app. For more information, go to name.
FUNCTION	Name of the specific function in the application where the error will be injected..	For example: myFunction. For more information, go to function.

Optional tunables

Common Tunables for Function Error Injection

Tunable	Description	Notes
TOTAL_CHAOS_DURATION	Total duration (in seconds) for which the error will be injected into the function.	Default: 60 s. For more information, go to duration of the chaos.
MESSAGE	Custom error message to be thrown by the function during chaos.	For example: Injected error for testing. For more information, go to message.

Name

The NAME env specifies the name of the target application that is under chaos.

---
# Injects error in a given function of the application pod
apiVersion: litmuschaos.io/v1alpha1
kind: K8sFault
metadata:
  name: pod-application-function-error
spec:
  definition:
    targets:
      application:
        name: 'my-app'
        function: 'myFunction'
    chaos:
      experiment: pod-application-function-error
      serviceAccountName: litmus-admin
      image: docker.io/harness/chaos-ddcr-faults:main-latest
      imagePullPolicy: Always
      env:
        - name: MESSAGE
          value: 'Injected error for testing'

Function

The FUNCTION env specifies the specific function in the application where the error will be injected.

---
# Injects error in a given function of the application pod
apiVersion: litmuschaos.io/v1alpha1
kind: K8sFault
metadata:
  name: pod-application-function-error
spec:
  definition:
    targets:
      application:
        name: 'my-app'
        function: 'myFunction'
    chaos:
      experiment: pod-application-function-error
      serviceAccountName: litmus-admin
      image: docker.io/harness/chaos-ddcr-faults:main-latest
      imagePullPolicy: Always
      env:
        - name: MESSAGE
          value: 'Injected error for testing'

Message

The MESSAGE environment variable specifies the exact error message to be thrown as part of the chaos fault injection.

---
# Injects error in a given function of the application pod
apiVersion: litmuschaos.io/v1alpha1
kind: K8sFault
metadata:
  name: pod-application-function-error
spec:
  definition:
    targets:
      application:
        name: 'my-app'
        function: 'myFunction'
    chaos:
      experiment: pod-application-function-error
      serviceAccountName: litmus-admin
      image: docker.io/harness/chaos-ddcr-faults:main-latest
      imagePullPolicy: Always
      env:
        - name: MESSAGE
          value: 'Injected error for testing'