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

This experiment consumes the Memory resources on the application container on specified memory in megabytes. It simulates conditions where app pods experience Memory spikes either due to expected/undesired processes thereby testing how the overall application stack behaves when this occurs. !!! tip "Scenario: Stress the Memory" ??? info "View the uses of the experiment" Memory usage within containers is subject to various constraints in Kubernetes. If the limits are specified in their spec, exceeding them can cause termination of the container (due to OOMKill of the primary process, often pid 1) - the restart of the container by kubelet, subject to the policy specified. For containers with no limits placed, the memory usage is uninhibited until such time as the Node level OOM Behaviour takes over. In this case, containers on the node can be killed based on their oom_score and the QoS class a given pod belongs to (bestEffort ones are first to be targeted). This eval is extended to all pods running on the node - thereby causing a bigger blast radius. This experiment launches a stress process within the target container - which can cause either the primary process in the container to be resource constrained in cases where the limits are enforced OR eat up available system memory on the node in cases where the limits are not specified ??? 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>pod-memory-hog-exec</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/pod-cpu-memory-exec/fault.yaml">here</a> ??? info "View the default validations" The application pods should be in running 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: pod-memory-hog-exec-sa namespace: default labels: name: pod-memory-hog-exec-sa app.kubernetes.io/part-of: litmus apiVersion: rbac.authorization.k8s.io/v1 kind: Role metadata: name: pod-memory-hog-exec-sa namespace: default labels: name: pod-memory-hog-exec-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: ["apps"] resources: ["deployments","statefulsets","replicasets", "daemonsets"] verbs: ["list","get"] apiGroups: ["apps.openshift.io"] resources: ["deploymentconfigs"] verbs: ["list","get"] apiGroups: [""] resources: ["replicationcontrollers"] verbs: ["get","list"] apiGroups: ["argoproj.io"] resources: ["rollouts"] verbs: ["list","get"] apiGroups: ["batch"] resources: ["jobs"] verbs: ["create","list","get","delete","deletecollection"] apiGroups: ["litmuschaos.io"] resources: ["chaosengines","chaosexperiments","chaosresults"] verbs: ["create","list","get","patch","update","delete"] apiVersion: rbac.authorization.k8s.io/v1 kind: RoleBinding metadata: name: pod-memory-hog-exec-sa namespace: default labels: name: pod-memory-hog-exec-sa app.kubernetes.io/part-of: litmus roleRef: apiGroup: rbac.authorization.k8s.io kind: Role name: pod-memory-hog-exec-sa subjects: kind: ServiceAccount name: pod-memory-hog-exec-sa namespace: default ``` Use this sample RBAC manifest to create a chaosServiceAccount in the desired (app)

This example consists of the minimum necessary role permissions to execute the experiment. ??? info "check the experiment tunables" <h2>Optional Fields</h2> <table> <tr> <th> Variables </th> <th> Description </th> <th> Notes </th> </tr> <tr> <td> MEMORY_CONSUMPTION </td> <td> The amount of memory used of hogging a Kubernetes pod (megabytes)</td> <td> Defaults to 500MB (Up to 2000MB)</td> </tr> <tr> <td> TOTALCHAOSDURATION </td> <td> The time duration for chaos insertion (seconds) </td> <td> Defaults to 60s </td> </tr> <td> LIB </td> <td> The chaos lib used to inject the chaos. Available libs are <code>litmus</code></td> <td> Defaults to <code>litmus</code> </td> </tr> <tr> <td> TARGET_PODS </td> <td> Comma separated list of application pod name subjected to pod memory hog chaos</td> <td> If not provided, it will select target pods randomly based on provided appLabels</td> </tr> <tr> <td> TARGET_CONTAINER </td> <td> Name of the target container under chaos </td> <td> If not provided, it will select the first container of the target pod </td> </tr> <tr> <td> CHAOSKILLCOMMAND </td> <td> The command to kill the chaos process </td> <td> Defaults to <code>kill $(find /proc -name exe -lname '*/dd' 2>&1 | grep -v 'Permission denied' | awk -F/ '{print $(NF-1)}' | head -n 1)</code>. Another useful one that generally works (in case the default doesn't) is <code>kill -9 $(ps afx | grep "[dd] if=/dev/zero" | awk '{print $1}' | tr '\n' ' ')</code>. In case neither works, please check whether the target pod's base image offers a shell. If yes, identify appropriate shell command to kill the chaos process </td> </tr> <tr> <td> PODSAFFECTEDPERC </td> <td> The Percentage of total pods to target </td> <td> Defaults to 0 (corresponds to 1 replica), provide numeric value only </td> </tr> <tr> <td> RAMP_TIME </td> <td> Period to wait before injection of chaos in sec </td> <td> </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 pod specific tunables. It stresses the `MEMORYCONSUMPTION` MB memory of the targeted pod for the `TOTALCHAOS_DURATION` duration. The memory consumption limit is 2000MB Use the following example to tune this: ```yaml apiVersion: litmuschaos.io/v1alpha1 kind: ChaosEngine metadata: name: engine-nginx spec: engineState: "active" annotationCheck: "false" appinfo: appns: "default" applabel: "app=nginx" appkind: "deployment" chaosServiceAccount: pod-memory-hog-sa experiments: name: pod-memory-hog spec: components: env: name: MEMORY_CONSUMPTION value: '500' #in MB name: TOTALCHAOSDURATION value: '60' ``` It defines the `CHAOSKILLCOMMAND` ENV to set the chaos kill command. Default values of `CHAOSKILLCOMMAND` command: `CHAOSKILLCOMMAND`: "kill $(find /proc -name exe -lname '*/dd' 2>&1 | grep -v 'Permission denied' | awk -F/ '{print $(NF-1)}' | head -n 1)" Use the following example to tune this: ```yaml apiVersion: litmuschaos.io/v1alpha1 kind: ChaosEngine metadata: name: engine-nginx spec: engineState: "active" annotationCheck: "false" appinfo: appns: "default" applabel: "app=nginx" appkind: "deployment" chaosServiceAccount: pod-memory-hog-exec-sa experiments: name: pod-memory-hog-exec spec: components: env: name: CHAOSKILLCOMMAND value: "kill $(find /proc -name exe -lname '*/dd' 2>&1 | grep -v 'Permission denied' | awk -F/ '{print $(NF-1)}' | head -n 1)" name: TOTALCHAOSDURATION value: '60' ```