Pod IO error

The pod IO error simulates an error that can occur during system calls of the files located within the mounted volume of the pod. When triggered, it causes the call to fail and return an error, potentially disrupting critical processes that rely on accurate file operations.

Use cases

Pod IO error:

• Simulates the error to test whether the application is able to recover gracefully from a failure in that service.
• Simulates errors into file system calls during a load test to see how the application responds, and whether it is able to handle the increased traffic,
• Simulates errors to test how your application responds to unexpected failures so you can plan accordingly.
• Simulates errors into file system call to test whether the application is vulnerable to attacks that exploit file system vulnerabilities.

warning

• Due to the large blast radius of this fault, we recommend you do not execute it in the production environment.
• Through the fault execution, the application pod can potentially fail to perform successful IO writes if the write system call is being targeted. This can cause any data produced in this duration to be lost.
• Any data produced before the execution of the fault is not harmed as a result of its execution.

Prerequisites

• Kubernetes > 1.16
• The application pods should be in the running state before and after injecting chaos.

Mandatory tunables

Tunable	Description	Notes
ERROR_CODE	Specify the error code to be injected in file system calls	For more information, go to error code.
MOUNT_PATH	The absolute mount path of the volume mounted to the target pod	For more information, go to mount path.

Optional tunables

Tunable	Description	Notes
TARGET_CONTAINER	Name of the container subject to IO error	If the value is not provided, the fault injects chaos on the first container of the pod. For more information, go to target specific container.
FILE_PATH	The path for injecting faults can be specified as either a single file or a wildcard. If not provided, it will target all the files present inside the mount path	For more information, go to file path.
PERCENTAGE	The likelihood of failure per operation, expressed as a percentage	For more information, go to percentage.
METHOD_TYPES	This contains the file system call or methods.	For more information, go to percentage.
CONTAINER_RUNTIME	Container runtime interface for the cluster	Default: containerd. Supports docker, containerd and crio. For more information, go to container runtime .
SOCKET_PATH	Path of the containerd or crio or docker socket file	Defaults to /run/containerd/containerd.sock. For more information, go to socket path.
TOTAL_CHAOS_DURATION	Duration to inject insert chaos (in seconds)	Default: 60 s.
NODE_LABEL	Node label used to filter the target node if TARGET_NODE environment variable is not set.	It is mutually exclusive with the TARGET_NODE environment variable. If both are provided, the fault uses TARGET_NODE. For more information, go to node label.
TARGET_PODS	Comma-separated list of application pod names subject to pod IO error	If not provided, the fault selects target pods randomly based on provided appLabels. For more information go to target specific pods.
LIB_IMAGE	Image used to inject chaos.	Default: chaosnative/chaos-go-runner:main-latest. For more information, go to image used by the helper pod.
PODS_AFFECTED_PERC	Percentage of total pods to target. Provide numeric values.	Default: 0 (corresponds to 1 replica). For more information, go to pod affected percentage.
RAMP_TIME	Period to wait before and after injecting chaos (in seconds)	For example, 30 s. For more information, go to ramp time.
SEQUENCE	Sequence of chaos execution for multiple target pods	Default: parallel. Supports serial and parallel. For more information, go to sequence of chaos execution.

Error code

Error code to be injected in system calls of the files located within the mounted volume of the pod. Tune it by using the ERROR_CODE environment variable.

The following YAML snippet illustrates the use of this environment variable:

# it injects io error in the file system calls
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  appinfo:
    appns: "default"
    applabel: "app=nginx"
    appkind: "deployment"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: pod-io-error
    spec:
      components:
        env:
        # error code
        - name: ERROR_CODE
          value: '5'
        - name: MOUNT_PATH
          value: '/etc/config'
        - name: TOTAL_CHAOS_DURATION
          value: '60'

Mount path

Mount path of the volume mounted to the target application. Tune it by using the MOUNT_PATH environment variable.

The following YAML snippet illustrates the use of this environment variable:

# it injects io error in the file system calls
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  appinfo:
    appns: "default"
    applabel: "app=nginx"
    appkind: "deployment"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: pod-io-error
    spec:
      components:
        env:
        # mount path of the volume
        - name: MOUNT_PATH
          value: '/etc/config'
        - name: ERROR_CODE
          value: '5'
        - name: TOTAL_CHAOS_DURATION
          value: '60'

Advanced fault tunables

• FILE_PATH: The path for injecting faults can be specified as either a single file or a wildcard. By default it targets all the files present inside the mount path.
• PERCENTAGE: The likelihood of failure per operation, expressed as a percentage. Default is 100%.
• METHOD_TYPES: This contains the file system call or methods. By default it targets all the methods.

The following YAML snippet illustrates the use of this environment variable:

# it injects io error in the file system calls
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  appinfo:
    appns: "default"
    applabel: "app=nginx"
    appkind: "deployment"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: pod-io-error
    spec:
      components:
        env:
        # filter the target files
        - name: FILE_PATH
          value: '/etc/config/file.txt'
        # percentage of i/o calls
        - name: PERCENTAGE
          value: '50'
        # names of the io methods
        - name: METHOD_TYPES
          value: '["read","write"]'
        - name: ERROR_CODE
          value: '5'
        - name: MOUNT_PATH
          value: '/etc/config'
        - name: TOTAL_CHAOS_DURATION
          value: '60'

Container runtime and socket path

The CONTAINER_RUNTIME and SOCKET_PATH are environment variables to set the container runtime and socket file path, respectively.

• CONTAINER_RUNTIME: This supports docker, containerd, and crio runtimes. The default value is containerd.
• SOCKET_PATH: This contains the path of containerd socket file by default (/run/containerd/containerd.sock). For docker, specify the path as /var/run/docker.sock. For crio, specify the path as /var/run/crio/crio.sock.

The following YAML snippet illustrates the use of these environment variables:

## provide the container runtime and socket file path
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  appinfo:
    appns: "default"
    applabel: "app=nginx"
    appkind: "deployment"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: pod-io-error
    spec:
      components:
        env:
        # runtime for the container
        # supports docker, containerd, crio
        - name: CONTAINER_RUNTIME
          value: 'containerd'
        # path of the socket file
        - name: SOCKET_PATH
          value: '/run/containerd/containerd.sock'
        - name: ERROR_CODE
          value: '5'
        - name: MOUNT_PATH
          value: '/etc/config'
        - name: TOTAL_CHAOS_DURATION
          VALUE: '60'