Time chaos

Time chaos is a Kubernetes pod-level fault that introduces controlled time offsets to disrupt the system time of the target pod.

For a video tutorial, go to time chaos that walks through the execution of the experiment.

Use cases

Time Chaos:

• Simulate scenarios where TLS certificates expire while the system is in operation. This allows them to assess how their applications, services, or infrastructure handle expired certificates in real-time.
• It is used to identify potential weaknesses in the system's ability to recover and handle time-related faults, leading to improvements in fault-tolerant designs and system resilience.
• It can be used in various simulations to mimic real-world scenarios where time synchronization or manipulation is critical.

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: time-chaos
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"]

Prerequisites

• Kubernetes > 1.16 is required to execute this fault.
• The application pods should be in the running state before and after injecting chaos.

Mandatory tunables

Tunable	Description	Notes
OFFSET	Offset value used to modify the system time	Default: 3600s. For more information, go to offset.

Optional tunables

Tunable	Description	Notes
TOTAL_CHAOS_DURATION	Duration for which to insert chaos (in seconds).	Default: 60 s. For more information, go to duration of the chaos.
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.
CLOCK_IDS	Comma separated clock ids of the target system clock	Default: CLOCK_REALTIME. For more information, go to offset.
TARGET_CONTAINER	Name of the container subject to time chaos	If this value is not provided, the fault selects the first container of the target pod. For more information, go to target specific container
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.
TARGET_PODS	Comma-separated list of application pod names subject to chaos	If not provided, the fault selects target pods randomly based on provided appLabels. For more information, go to target specific pods.
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.
SEQUENCE	Sequence of chaos execution for multiple target pods.	Default: parallel. Supports serial and parallel. For more information, go to sequence of chaos execution.
LIB_IMAGE	Image used to inject chaos.	Default: harness/chaos-go-runner:main-latest. For more information, go to image used by the helper pod.
RAMP_TIME	Period to wait before and after injecting chaos (in seconds).	For example, 30 s. For more information, go to ramp time.

Offset and Clock IDs

The OFFSET and CLOCK_IDS environment variables set the offset and clock ids, respectively.

• OFFSET: Offset value used to modify the system time. It should match with ^(\d+)(ms|s|m|h)$ regex.
• CLOCK_IDS: Comma separated clock ids of the target system clock. Refer to 'uapi/linux/time.h' for more details.

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

## provide the offset and clock ids
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: time-chaos
      spec:
        components:
          env:
            # time offset
            - name: OFFSET
              value: "3600s"
            # clock ids of the target system
            - name: CLOCK_IDS
              value: "CLOCK_REALTIME"
            - name: TOTAL_CHAOS_DURATION
              VALUE: "60"

Container runtime and socket path

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

• CONTAINER_RUNTIME: It supports docker, containerd, and crio runtimes. The default value is containerd.
• SOCKET_PATH: It contains 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 this environment variable:

## 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: time-chaos
      spec:
        components:
          env:
            # time offset
            - name: OFFSET
              value: "3600s"
            # 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: TOTAL_CHAOS_DURATION
              VALUE: "60"