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Pod API modify header

Introduction​

Pod API modify header is a Kubernetes pod-level chaos fault that overrides the header values of API requests and responses with the user-provided values for the given keys. This is achieved by starting the proxy server and redirecting the traffic through the proxy server.

Pod API Modify Header

Use cases​

Pod API modify header:

  • Simulate different authentication states or test the behavior of your application when using invalid or expired credentials.
  • This fault can be utilized to validate the caching behavior of your API or client applications. By overriding cache-related headers, such as the "Cache-Control" or "ETag" headers, you can simulate cache validation scenarios.
  • It can be used to test content negotiation capabilities. By modifying the "Accept" header in the API request, you can simulate different content types or formats that the client application can accept.
note
  • Kubernetes> 1.17 is required to execute this fault.
  • The application pods should be in the running state before and after injecting chaos.

Fault tunables​

Mandatory tunables

Tunable Description Notes
TARGET_SERVICE_PORT Port of the target service. Defaults to port 80. For more information, go to target service port.
HEADERS_MAP Map of the headers to modify or add For example, {"X-Litmus-Test-Header": "X-Litmus-Test-Value"}. To remove a header, just set the value to ""; For example, {"X-Litmus-Test-Header": ""}. For more information, go to headers map.
PATH_FILTER Api path or route used for the filtering For more information, go to path filter .

Optional tunables

Tunable Description Notes
PROXY_PORT Port where the proxy listens for requests. Default: 20000. For more information, go to proxy port.
SERVICE_DIRECTION Direction of the flow of control, ingress or egress Default: `ingress`. For more information, go to service direction .
DATA_DIRECTION API payload type, request or response Default: `both`. For more information, go to data direction .
NETWORK_INTERFACE Network interface used for the proxy. Default: `eth0`. For more information, go to network interface .
CONTAINER_RUNTIME Container runtime interface for the cluster Default: containerd. Support values: docker, containerd and crio. For more information, go to container runtime .
SOCKET_PATH Path of the containerd or crio or docker socket file. Default: /run/containerd/containerd.sock. For more information, go to socket path.
TOTAL_CHAOS_DURATION Duration of chaos injection (in seconds). Default: 60 s. For more information, go to duration of the chaos .
TARGET_PODS Comma-separated list of application pod names subject to pod HTTP modify body. 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
RAMP_TIME Period to wait before and after injecting chaos (in seconds). For example, 30 s. For more information, go to ramp time.
SEQUENCE Sequence of chaos execution for multiple target pods. Default: parallel. Supports serial and parallel. For more information, go to sequence of chaos execution.

Target service port​

Port of the targeted service. Tune it by using the TARGET_SERVICE_PORT environment variable.

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

## provide the port of the targeted service
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: pod-api-modify-header
      spec:
        components:
          env:
            # provide the port of the targeted service
            - name: TARGET_SERVICE_PORT
              value: "80"
            - name: HEADERS_MAP
              value: '{"X-Litmus-Test-Header": "X-Litmus-Test-Value"}'
            - name: PATH_FILTER
              value: '/status'

Headers map​

Map of the headers that need to be modified or added to the HTTP request or response. Tune it by using the HEADERS_MAP environment variable.

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

## provide the headers as a map
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: pod-api-modify-header
      spec:
        components:
          env:
            # map of headers to modify/add; Eg: {"X-Litmus-Test-Header": "X-Litmus-Test-Value"}
            # to remove a header, just set the value to ""; Eg: {"X-Litmus-Test-Header": ""}
            - name: HEADERS_MAP
              value: '{"X-Litmus-Test-Header": "X-Litmus-Test-Value"}'
            # provide the port of the targeted service
            - name: TARGET_SERVICE_PORT
              value: "80"
            - name: PATH_FILTER
              value: '/status'

Path Filter​

API sub path/route to filter the api calls. Tune it by using the PATH_FILTER environment variable.

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

## provide api path filter
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: pod-api-modify-header
      spec:
        components:
          env:
            # provide the api path filter
            - name: PATH_FILTER
              value: '/status'
            - name: HEADERS_MAP
              value: '{"X-Litmus-Test-Header": "X-Litmus-Test-Value"}'
            # provide the port of the targeted service
            - name: TARGET_SERVICE_PORT
              value: "80"

Destination ports​

A comma-separated list of the destination service or host ports for which egress traffic should be affected as a result of chaos testing on the target application. Tune it by using the DESTINATION_PORTS environment variable.

note

It is applicable only for the egress SERVICE_DIRECTION.

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

## provide destination ports
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: pod-api-modify-header
      spec:
        components:
          env:
            # provide destination ports
            - name: DESTINATION_PORTS
              value: '80,443'
            # provide the api path filter
            - name: PATH_FILTER
              value: '/status'
            - name: HEADERS_MAP
              value: '{"X-Litmus-Test-Header": "X-Litmus-Test-Value"}'
            # provide the port of the targeted service
            - name: TARGET_SERVICE_PORT
              value: "80"

HTTPS enabled​

This item is employed to facilitate HTTPS for both incoming and outgoing traffic, and its usage can vary depending on whether it's applied to ingress or egress scenarios. Tune it by using the HTTPS_ENABLED environment variable.

  • When applied to ingress traffic, it should be configured as true if the HTTPS URL of the target application includes a port, following the format https://<hostname>:port. However, for HTTPS URLs in the form of https://<hostname> without a port, this setting is not required.

  • For egress traffic, setting it to true is necessary to enable HTTPS support for external services, which will then establish TLS certificates for the proxy within the target application.

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

## enable https support
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: pod-api-modify-header
      spec:
        components:
          env:
            # enable https support
            - name: HTTPS_ENABLED
              value: 'true'
            # provide the api path filter
            - name: PATH_FILTER
              value: '/status'
            - name: HEADERS_MAP
              value: '{"X-Litmus-Test-Header": "X-Litmus-Test-Value"}'
            # provide the port of the targeted service
            - name: TARGET_SERVICE_PORT
              value: "80"

Advanced fault tunables​

  • PROXY_PORT: Port where the proxy listens for requests and responses.
  • SERVICE_DIRECTION: Direction of the flow of control, either ingress or egress. It supports ingress, egress values.
  • DATA_DIRECTION: API payload type, request, or response. It supports request, response, and both values.
  • NETWORK_INTERFACE: Network interface used for the proxy.

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

# it injects the api modify header fault
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: pod-api-modify-header
      spec:
        components:
          env:
            # provide the proxy port
            - name: PROXY_PORT
              value: '20000'
            # provide the connection type
            - name: SERVICE_DIRECTION
              value: 'ingress'
            # provide the payload type
            - name: DATA_DIRECTION
              value: 'both'
            # provide the network interface
            - name: NETWORK_INTERFACE
              value: 'eth0'
            # provide the api path filter
            - name: PATH_FILTER
              value: '/status'
            # provide the port of the targeted service
            - name: TARGET_SERVICE_PORT
              value: "80"
            - name: HEADERS_MAP
              value: '{"X-Litmus-Test-Header": "X-Litmus-Test-Value"}'

Container runtime and socket path​

The CONTAINER_RUNTIME and SOCKET_PATH environment variable to 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 path as /var/run/docker.sock. For crio, specify path as /var/run/crio/crio.sock.

The following YAML snippet illustrates the use of these environment variables:

## 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: pod-api-modify-header
      spec:
        components:
          env:
            # 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"
            # provide the port of the targeted service
            - name: TARGET_SERVICE_PORT
              value: "80"
            # provide the api path filter
            - name: PATH_FILTER
              value: '/status'
            - name: HEADERS_MAP
              value: '{"X-Litmus-Test-Header": "X-Litmus-Test-Value"}'