Project: Litmus (Observability and Analysis / Chaos Engineering)
File: pod-http-modify-body.md

It injects http modify body chaos on the service whose port is provided as `TARGETSERVICEPORT` by starting proxy server and then redirecting the traffic through the proxy server. Can be used to overwrite the http response body by providing the new body value as `RESPONSE_BODY`. It can test the application's resilience to error or incorrect http response body. !!! tip "Scenario: Modify Body of the HTTP response" ??? info "View the uses of the experiment" coming soon ??? info "Verify the prerequisites" Ensure that Kubernetes Version > 1.17 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-http-modify-body</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-http-modify-body/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-http-modify-body-sa namespace: default labels: name: pod-http-modify-body-sa app.kubernetes.io/part-of: litmus apiVersion: rbac.authorization.k8s.io/v1 kind: Role metadata: name: pod-http-modify-body-sa namespace: default labels: name: pod-http-modify-body-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-http-modify-body-sa namespace: default labels: name: pod-http-modify-body-sa app.kubernetes.io/part-of: litmus roleRef: apiGroup: rbac.authorization.k8s.io kind: Role name: pod-http-modify-body-sa subjects: kind: ServiceAccount name: pod-http-modify-body-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

??? info "check the experiment tunables" <h2>Mandatory Fields</h2> <table> <tr> <th> Variables </th> <th> Description </th> <th> Notes </th> </tr> <tr> <td> TARGETSERVICEPORT </td> <td> Port of the service to target</td> <td>Defaults to port 80 </td> </tr> <tr> <td> RESPONSE_BODY </td> <td> Body string to overwrite the http response body</td> <td> If no value is provided, response will be an empty body. Defaults to empty body </td> </tr> </table> <h2>Optional Fields</h2> <table> <tr> <th> Variables </th> <th> Description </th> <th> Notes </th> </tr> <tr> <td> CONTENT_ENCODING </td> <td> Encoding type to compress/encodde the response body </td> <td> Accepted values are: gzip, deflate, br, identity. Defaults to none (no encoding) </td> </td> <tr> <td> CONTENT_TYPE </td> <td> Content type of the response body </td> <td> Defaults to text/plain </td> </tr> <tr> <td> PROXY_PORT </td> <td> Port where the proxy will be listening for requests</td> <td> Defaults to 20000 </td> </tr> <tr> <td> NETWORK_INTERFACE </td> <td> Network interface to be used for the proxy</td> <td> Defaults to `eth0` </td> </tr> <tr> <td> TOXICITY </td> <td> Percentage of HTTP requests to be affected </td> <td> Defaults to 100 </td> </tr> <tr> <td> CONTAINER_RUNTIME </td> <td> container runtime interface for the cluster</td> <td> Defaults to containerd, supported values: docker, containerd and crio for litmus and only docker for pumba LIB </td> </tr> <tr> <td> SOCKET_PATH </td> <td> Path of the containerd/crio/docker socket file </td> <td> Defaults to `/run/containerd/containerd.sock` </td> </tr> <tr> <td> TOTALCHAOSDURATION </td> <td> The duration of chaos injection (seconds) </td> <td> Default (60s) </td> </tr> <tr> <td> TARGET_PODS </td> <td> Comma separated list of application pod name subjected to pod http modify body chaos</td> <td> If not provided, it will select target pods randomly based on provided appLabels</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> LIB_IMAGE </td> <td> Image used to run the netem command </td> <td> Defaults to `litmuschaos/go-runner:latest` </td> </tr> <tr> <td> RAMP_TIME </td> <td> Period to wait before and after 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 defines the port of the targeted service that is being targeted. It can be tuned via `TARGETSERVICEPORT` ENV. 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-http-modify-body-sa experiments: name: pod-http-modify-body spec: components: env: name: TARGETSERVICEPORT value: "80" name: RESPONSE_BODY value: '2000' ``` It defines the port on which the proxy server will listen for requests. It can be tuned via `PROXY_PORT`

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-http-modify-body-sa experiments: name: pod-http-modify-body spec: components: env: name: PROXY_PORT value: '8080' name: TARGETSERVICEPORT value: "80" ``` It defines the body string that will overwrite the http response body. It can be tuned via `RESPONSE_BODY` ENV. 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-http-modify-body-sa experiments: name: pod-http-modify-body spec: components: env: name: RESPONSE_BODY value: '2000' name: TARGETSERVICEPORT value: "80" ``` It defines the toxicity value to be added to the http request. It can be tuned via `TOXICITY` ENV. Toxicity value defines the percentage of the total number of http requests to be affected. 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-http-modify-body-sa experiments: name: pod-http-modify-body spec: components: env: name: TOXICITY value: "100" name: TARGETSERVICEPORT value: "80" ``` It defines the content encoding and content type of the response body. It can be tuned via `CONTENTENCODING` and `CONTENTTYPE` ENV. 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-http-modify-body-sa experiments: name: pod-http-modify-body spec: components: env: name: CONTENT_ENCODING value: 'gzip' name: CONTENT_TYPE value: 'text/html' name: RESPONSE_BODY value: '2000' name: TARGETSERVICEPORT value: "80" ``` It defines the network interface to be used for the proxy. It can be tuned via `NETWORK_INTERFACE` ENV. 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-http-modify-body-sa experiments: name: pod-http-modify-body spec: components: env: name: NETWORK_INTERFACE value: "eth0" name: TARGETSERVICEPORT value: '80' name: RESPONSE_BODY value: '2000' ``` It defines the `CONTAINERRUNTIME` and `SOCKETPATH` ENV to set the container runtime and socket file path. `CONTAINER_RUNTIME`: It supports `docker`, `containerd`, and `crio` runtimes. The default value is `docker`. `SOCKET_PATH`: It contains path of docker socket file by default(`/run/containerd/containerd.sock`). For other runtimes provide the appropriate path. 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-http-modify-body-sa experiments: name: pod-http-modify-body spec: components: env: name: CONTAINER_RUNTIME value: 'containerd' name: SOCKET_PATH value: '/run/containerd/containerd.sock' name: TARGETSERVICEPORT value: "80" name: RESPONSE_BODY value: '2000' ```