Project: Litmus (Observability and Analysis / Chaos Engineering)
File: node-memory-hog.md

This experiment causes Memory resource exhaustion on the Kubernetes node. The experiment aims to verify resiliency of applications whose replicas may be evicted on account on nodes turning unschedulable (Not Ready) due to lack of Memory resources. The Memory chaos is injected using a helper pod running the linux stress-ng tool (a workload generator)- The chaos is effected for a period equalling the TOTALCHAOSDURATION and upto MEMORYCONSUMPTIONPERCENTAGE(out of 100) or MEMORYCONSUMPTIONMEBIBYTES(in Mebibytes out of total available memory). Application implies services. Can be reframed as: Tests application resiliency upon replica evictions caused due to lack of Memory resources !!! tip "Scenario: Stress the memory of node" ??? info "View the uses of the experiment" coming soon ??? info "Verify the prerequisites" Ensure that Kubernetes Version > 1.16 Ensure that the Litmus Chaos Operator is running by executing <code>kubectl get pods</code> in operator namespace (typically, <code>litmus</code>).If not, install from <a href="https://v1-docs.litmuschaos.io/docs/getstarted/#install-litmus">here</a> Ensure that the <code>node-memory-hog</code> experiment resource is available in the cluster by executing <code>kubectl get chaosexperiments</code> in the desired namespace. If not, install from <a href="https://hub.litmuschaos.io/api/chaos/master?file=faults/kubernetes/node-memory-hog/fault.yaml">here</a> ??? info "View the default validations" The target nodes should be in ready state before and after chaos injection. !!! tip "NOTE" If you are using this experiment as part of a litmus workflow scheduled constructed & executed from chaos-center, then you may be making use of the RBAC, which is pre installed in the cluster as part of the agent setup. ??? note "View the Minimal RBAC permissions" ```yaml apiVersion: v1 kind: ServiceAccount metadata: name: node-memory-hog-sa namespace: default labels: name: node-memory-hog-sa app.kubernetes.io/part-of: litmus apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRole metadata: name: node-memory-hog-sa labels: name: node-memory-hog-sa app.kubernetes.io/part-of: litmus rules: apiGroups: [""] resources: ["pods"] verbs: ["create","delete","get","list","patch","update", "deletecollection"] apiGroups: [""] resources: ["events"] verbs: ["create","get","list","patch","update"] apiGroups: [""] resources: ["configmaps"] verbs: ["get","list",] apiGroups: [""] resources: ["pods/log"] verbs: ["get","list","watch"] apiGroups: [""] resources: ["pods/exec"] verbs: ["get","list","create"] apiGroups: ["batch"] resources: ["jobs"] verbs: ["create","list","get","delete","deletecollection"] apiGroups: ["litmuschaos.io"] resources: ["chaosengines","chaosexperiments","chaosresults"] verbs: ["create","list","get","patch","update","delete"] apiGroups: [""] resources: ["nodes"] verbs: ["get","list"] apiVersion: rbac.authorization.k8s.io/v1 kind: ClusterRoleBinding metadata: name: node-memory-hog-sa labels: name: node-memory-hog-sa app.kubernetes.io/part-of: litmus roleRef: apiGroup: rbac.authorization.k8s.io kind: ClusterRole name: node-memory-hog-sa subjects: kind: ServiceAccount name: node-memory-hog-sa namespace: default ``` Use this sample RBAC manifest to create a chaosServiceAccount in the desired (app) namespace. This example consists of the minimum necessary role permissions to execute the experiment. ??? info "check the experiment tunables" <h2>Mandatory Fields</h2> <table> <tr> <th> Variables </th> <th> Description </th> <th> Notes </th> </tr> <tr> <td> TARGET_NODES </td> <td> Comma separated list of nodes, subjected to node memory hog chaos</td> <td> </td> </tr> <tr> <td> NODE_LABEL </td> <td> It contains node label, which will be used to filter the target nodes if TARGET_NODES ENV is not set </td> <td>It is mutually exclusive with the TARGETNODES

If both are provided then it will use the TARGETNODES</td> </tr> </table> <h2>Optional Fields</h2> <table> <tr> <th> Variables </th> <th> Description </th> <th> Notes </th> </tr> <tr> <td> TOTALCHAOSDURATION </td> <td> The time duration for chaos insertion (in seconds) </td> <td> Optional </td> <td> Defaults to 120 </td> </tr> <tr> <td> LIB </td> <td> The chaos lib used to inject the chaos </td> <td> Optional </td> <td> Defaults to `litmus` </td> </tr> <tr> <td> LIB_IMAGE </td> <td> Image used to run the stress command </td> <td> Optional </td> <td> Defaults to <code>litmuschaos/go-runner:latest</code> </td> </tr> <tr> <td> MEMORYCONSUMPTIONPERCENTAGE </td> <td> Percent of the total node memory capacity </td> <td> Optional </td> <td> Defaults to 30 </td> </tr> </tr> <tr> <td> MEMORYCONSUMPTIONMEBIBYTES </td> <td> The size in Mebibytes of total available memory. When using this we need to keep MEMORYCONSUMPTIONPERCENTAGE empty as the percentage have more precedence</td> <td> Optional </td> <td> </td> </tr> <tr> <td> NUMBEROFWORKERS </td> <td> It is the number of VM workers involved in IO disk stress </td> <td> Optional </td> <td> Default to 1 </td> </tr> <tr> <td> RAMP_TIME </td> <td> Period to wait before and after injection of chaos in sec </td> <td> Optional </td> <td> </td> </tr> <tr> <td> NODESAFFECTEDPERC </td> <td> The Percentage of total nodes to target </td> <td> Optional </td> <td> Defaults to 0 (corresponds to 1 node), provide numeric value only </td> </tr> <tr> <td> SEQUENCE </td> <td> It defines sequence of chaos execution for multiple target pods </td> <td> Default value: parallel. Supported: serial, parallel </td> </tr> </table> Refer the and to tune the common tunables for all experiments and node specific tunables. It stresses the `MEMORYCONSUMPTIONPERCENTAGE` percentage of total node capacity of the targeted node. Use the following example to tune this: ```yaml apiVersion: litmuschaos.io/v1alpha1 kind: ChaosEngine metadata: name: engine-nginx spec: engineState: "active" annotationCheck: "false" chaosServiceAccount: node-memory-hog-sa experiments: name: node-memory-hog spec: components: env: name: MEMORYCONSUMPTIONPERCENTAGE value: '10' # in percentage name: TOTALCHAOSDURATION value: '60' ``` It stresses the `MEMORYCONSUMPTIONMEBIBYTES` MiBi of the memory of the targeted node. It is mutually exclusive with the `MEMORYCONSUMPTIONPERCENTAGE` ENV. If `MEMORYCONSUMPTIONPERCENTAGE` ENV is set then it will use the percentage for the stress otherwise, it will stress the i/o based on `MEMORYCONSUMPTIONMEBIBYTES` ENV. Use the following example to tune this: ```yaml apiVersion: litmuschaos.io/v1alpha1 kind: ChaosEngine metadata: name: engine-nginx spec: engineState: "active" annotationCheck: "false" chaosServiceAccount: node-memory-hog-sa experiments: name: node-memory-hog spec: components: env: name: MEMORYCONSUMPTIONMEBIBYTES value: '500' # in MiBi name: TOTALCHAOSDURATION value: '60' ``` The workers count for the stress can be tuned with `NUMBEROFWORKERS` ENV. Use the following example to tune this: ```yaml apiVersion: litmuschaos.io/v1alpha1 kind: ChaosEngine metadata: name: engine-nginx spec: engineState: "active" annotationCheck: "false" chaosServiceAccount: node-memory-hog-sa experiments: name: node-memory-hog spec: components: env: name: NUMBEROFWORKERS value: '1' name: TOTALCHAOSDURATION value: '60' ```