Node memory hog

Node memory hog causes memory resource exhaustion on the Kubernetes node.

• It is injected using a helper pod running the Linux stress-ng tool (a workload generator).
• The chaos affects the application for a duration specified by the TOTAL_CHAOS_DURATION environment variable.

Usage

View fault usage

Node memory hog causes memory resource exhaustion on the Kubernetes node. The fault aims to verify resilience of applications whose replicas may be evicted on account on nodes becoming unschedulable (Not Ready) due to lack of memory resources. It simulates the situation of memory leaks in the deployment of microservices, application slowness due to memory starvation, and noisy neighbour problems due to hogging. It verifies pod priority and QoS setting for eviction purposes. It also verifies application restarts on OOM kills.

Default validations

The target nodes should be in the ready state before and after injecting chaos.

Fault tunables

Fault tunables

Mandatory fields

Variables	Description	Notes
TARGET_NODES	Comma-separated list of nodes subject to node I/O stress.	For example, node-1,node-2.
NODE_LABEL	It contains the node label that is used to filter the target nodes.	It is mutually exclusive with the TARGET_NODES environment variable. If both are provided, TARGET_NODES takes precedence.

Optional fields

Variables	Description	Notes
TOTAL_CHAOS_DURATION	Duration that you specify, through which chaos is injected into the target resource (in seconds).	Default to 120s.
LIB_IMAGE	Image used to run the stress command.	Defaults to litmuschaos/go-runner:latest.
MEMORY_CONSUMPTION_PERCENTAGE	Percent of the total node memory capacity.	Defaults to 30.
MEMORY_CONSUMPTION_MEBIBYTES	Amount of the total available memory (in mebibytes). It is mutually exclusive with MEMORY_CONSUMPTION_PERCENTAGE.	For example, 256.
NUMBER_OF_WORKERS	Number of VM workers involved in the stress.	Defaults to 1.
RAMP_TIME	Period to wait before and after injecting chaos (in seconds).	For example, 30s.
NODES_AFFECTED_PERC	Percentage of the total nodes to target. It takes numeric values only.	Defaults to 0 (corresponds to 1 node).
SEQUENCE	Sequence of chaos execution for multiple target pods.	Defaults to parallel. Supports serial sequence as well.

Fault examples

Common and node-specific tunables

Refer to the common attributes and node-specific tunables to tune the common tunables for all faults and node specific tunables.

Memory consumption percentage

It specifies the amount of memory consumed (in percentage). You can tune it using the MEMORY_CONSUMPTION_PERCENTAGE environment variable.

Use the following example to tune this:

# stress the memory of the targeted node with MEMORY_CONSUMPTION_PERCENTAGE of node capacity
# it is mutually exclusive with the MEMORY_CONSUMPTION_MEBIBYTES.
# if both are provided then it will use MEMORY_CONSUMPTION_PERCENTAGE for stress
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: node-memory-hog
    spec:
      components:
        env:
        # percentage of total node capacity to be stressed
        - name: MEMORY_CONSUMPTION_PERCENTAGE
          value: '10' # in percentage
        - name: TOTAL_CHAOS_DURATION
          VALUE: '60'

Memory consumption mebibytes

It specifies the amount of memory available. You can tune it using the MEMORY_CONSUMPTION_MEBIBYTES environment variable. It is mutually exclusive with the MEMORY_CONSUMPTION_PERCENTAGE environment variable. If MEMORY_CONSUMPTION_PERCENTAGE environment variable is set, then it uses this value for the stress.

Use the following example to tune it:

# stress the memory of the targeted node with given MEMORY_CONSUMPTION_MEBIBYTES
# it is mutually exclusive with the MEMORY_CONSUMPTION_PERCENTAGE.
# if both are provided then it will use MEMORY_CONSUMPTION_PERCENTAGE for stress
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: node-memory-hog
    spec:
      components:
        env:
        # node memory to be stressed
        - name: MEMORY_CONSUMPTION_MEBIBYTES
          value: '500' # in MiBi
        - name: TOTAL_CHAOS_DURATION
          VALUE: '60'

Workers for stress

It specifies the number of workers for stress. You can tune it using the NUMBER_OF_WORKERS environment variable.

Use the following example to tune it:

# provide for the workers count for the stress
apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: engine-nginx
spec:
  engineState: "active"
  annotationCheck: "false"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: node-memory-hog
    spec:
      components:
        env:
        # total number of workers involved in stress
        - name: NUMBER_OF_WORKERS
          value: '1' 
        - name: TOTAL_CHAOS_DURATION
          VALUE: '60'