Pod API block

Pod API block is a Kubernetes pod-level chaos fault that blocks the API requests through path filtering. This is achieved by starting the proxy server and redirecting the traffic through the proxy server during the chaos duration.

A transient proxy (also known as helper pod) is brought up for a chaos duration to intercept the requests made from the target application to another service and elsewhere, and inject chaos accordingly. Target application refers to the application pods calling/sending egress traffic to an endpoint.

Use cases

Pod API block:

• Validates how well your system can handle disruptions in API services for a specific pod.
• Ensures that your load balancer is effectively distributing traffic to healthy pods in the cluster.
• Checks if your system's failover mechanisms work as expected when one of the pods becomes unresponsive.
• Evaluates if your system can gracefully degrade performance when a specific component (in this case, a pod) is experiencing issues.

Permissions required

Below is a sample Kubernetes role that defines the permissions required to execute the fault.

apiVersion: rbac.authorization.k8s.io/v1
kind: Role
metadata:
  namespace: hce
  name: pod-api-block
spec:
  definition:
    scope: Cluster # Supports "Namespaced" mode too
permissions:
  - apiGroups: [""]
    resources: ["pods"]
    verbs: ["create", "delete", "get", "list", "patch", "deletecollection", "update"]
  - apiGroups: [""]
    resources: ["events"]
    verbs: ["create", "get", "list", "patch", "update"]
  - apiGroups: [""]
    resources: ["pods/log"]
    verbs: ["get", "list", "watch"]
  - apiGroups: [""]
    resources: ["deployments, statefulsets"]
    verbs: ["get", "list"]
  - apiGroups: [""]
    resources: ["replicasets, daemonsets"]
    verbs: ["get", "list"]
  - apiGroups: [""]
    resources: ["chaosEngines", "chaosExperiments", "chaosResults"]
    verbs: ["create", "delete", "get", "list", "patch", "update"]
  - apiGroups: ["batch"]
    resources: ["jobs"]
    verbs: ["create", "delete", "get", "list", "deletecollection"]

Prerequisites

• Kubernetes > 1.17
• The application pods should be running before and after injecting chaos.

Mandatory tunables

Tunable	Description	Notes
TARGET_CONTAINER	Name of the container subject to API block.	None. For more information, go to target specific container
TARGET_SERVICE_PORT	Port of the target service.	Default: port 80. For more information, go to target service port.

Optional tunables

Tunable	Description	Notes
PATH_FILTER	API path or route used for the filtering.	Targets all paths if not provided. For more information, go to path filter .
HEADERS_FILTERS	Filters for HTTP request headers accept multiple comma-separated headers in the format key1:value1,key2:value2.	For more information, go to header filters.
METHODS	The HTTP request method type accepts comma-separated HTTP methods in upper cases, such as "GET,POST".	For more information, go to methods.
QUERY_PARAMS	HTTP request query parameter filters accept multiple comma-separated query parameters in the format of param1:value1,param2:value2.	For more information, go to query params.
SOURCE_HOSTS	Includes comma-separated source host names as filters, indicating the origin of the HTTP request. This is specifically relevant to the "ingress" type.	For more information, go to source hosts.
SOURCE_IPS	This includes comma-separated source IPs as filters, indicating the origin of the HTTP request. This is specifically relevant to the "ingress" type.	For more information, go to source IPs.
DESTINATION_HOSTS	Comma-separated destination host names are used as filters, indicating the hosts on which you call the API. This specification applies exclusively to the "egress" type.	For more information, go to destination hosts.
DESTINATION_IPS	Comma-separated destination IPs are used as filters, indicating the hosts on which you call the API. This specification applies exclusively to the "egress" type.	For more information, go to destination hosts.
PROXY_PORT	Port where the proxy listens for requests.	Default: 20000. For more information, go to proxy port.
LIB_IMAGE	Image used to inject chaos.	Default: harness/chaos-go-runner:main-latest. For more information, go to image used by the helper pod.
SERVICE_DIRECTION	Direction of the flow of control, ingress or egress.	Default: ingress. For more information, go to service direction .
DESTINATION_PORTS	Comma-separated list of the destination service or host ports for which egress traffic should be affected.	Default: 80,443. For more information, go to destination ports.
HTTPS_ENABLED	Facilitate HTTPS support for both incoming and outgoing traffic.	Default: false. For more information, go to HTTPS.
CA_CERTIFICATES	These CA certificates are used by the proxy server to generate the server certificates for the TLS handshake between the target application and the proxy server.	These CA certificates must also be added to the target application's root certificate. For more information, go to CA certificates.
SERVER_CERTIFICATES	These server certificates are used by the proxy server for the TLS handshake between the target application and the proxy server.	The corresponding CA certificates should be loaded as root certificates inside the target application. For more information, go to server certificates.
HTTPS_ROOT_CERT_PATH	Provide the root CA certificate directory path.	This setting must be configured if the root CA certificate directory differs from /etc/ssl/certs. Go to root Linux for the default certificate directory based on various Linux distributions. For more information, go to HTTPS.
HTTPS_ROOT_CERT_FILE_NAME	Provide the root CA certificate file name.	This setting must be configured if the root CA certificate file name differs from ca-certificates.crt. Go to [root Linux] (https://go.dev/src/crypto/x509/root_linux.go) for the default certificate file names based on various Linux distributions. For more information, go to HTTPS.
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 .
NODE_LABEL	Node label used to filter the target node if TARGET_NODE environment variable is not set.	It is mutually exclusive with the TARGET_NODE environment variable. If both are provided, the fault uses TARGET_NODE. For more information, go to node label.
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 target 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-block
      spec:
        components:
          env:
            # provide the port of the targeted service
            - name: TARGET_SERVICE_PORT
              value: "80"
            - name: PATH_FILTER
              value: '/status'

Path filter

API sub-path (or 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-block
      spec:
        components:
          env:
            # provide the api path filter
            - name: PATH_FILTER
              value: '/status'
            # provide the port of the targeted service
            - name: TARGET_SERVICE_PORT
              value: "80"

Destination ports

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.

tip

It is applicable only when the SERVICE_DIRECTION environment variable is set to egress .

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-block
      spec:
        components:
          env:
            # provide destination ports
            - name: DESTINATION_PORTS
              value: '80,443'
            # provide the api path filter
            - name: PATH_FILTER
              value: '/status'
            # provide the port of the targeted service
            - name: TARGET_SERVICE_PORT
              value: "80"

HTTPS

To enable HTTPS support for both incoming and outgoing traffic between the target and the proxy, set the HTTPS_ENABLED field to true. The next step is to configure TLS, for which you can follow one of the ways

• Using self-signed certificate
• Using trusted certificate

Using Self-Signed Certificates

To establish TLS communication between the target application and the proxy server, you can use one of the following.

1. CA certificates

   The certificates provided by CA (or self-signed) to sign or validate the server certificates.

   • ca.key: The private key used to generate CA certificates.

   • ca.crt: The actual CA certificate.

   • Prerequisite: Load the ca.crt as the root CA certificate in the target application before experiment creation or execution.

   • Fault Configuration: Provide base64-encoded ca.key and ca.crt in the CA_CERTIFICATES environment variable.

     cat ca.key ca.crt > ca.pem
     cat ca.pem | base64  # Add this to the CA_CERTIFICATES environment variable

   In this setup, the proxy dynamically generates the server certificates with appropriate domain names during TLS handshake and sign them by the self-signed CA (provided in CA_CERTIFICATES environemtn variable) before sending them to the target application server.

2. Server certificates

   The certificates used by the transient proxy server for TLS handshake with the target application.

   • server.key: The private key used to generate the server certificates.

   • server.crt: The actual Server certificate (signed by the CA).

   • Internal Domain: Domain in which the local (organization-managed) services are deployed. Typically, it contains the local upstream or soft microservice dependencies.

   • External Domain: Domain in which the third-party services are deployed (for example, AWS services like DynamoDB or S3). Typically, it comprises the hard dependencies.

   • SAN (Subject Alternative Names): List of domain names provided to the cert-generation command or within the config file (*.cnf) passed as args to the cert-generators while creating the CSR (Certificate Signing Request).

   • Prerequisites: Load the ca.crt as the root CA certificate in the target application before experiment creation or execution. Create a server.crt with the necessary domain names and sign it using CA certificates.

   • Fault Configuration: Provide base64-encoded server.key and server.crt in the SERVER_CERTIFICATES environment variable.

     cat server.key server.crt > server.pem
     cat server.pem | base64  # Add this to the SERVER_CERTIFICATES environment variable

   In this setup, the proxy sends the server certificates (provided in SERVER_CERTIFICATES environment variable) to the target application server as part of the TLS handshake.

note

Intermediate Certificates are the chain of certificates that are used to generate the eventual server certificate for security purposes.

Using Trusted Certificates

You can use trusted server certificates for internal or external domains, both of which are described below.

1. For Internal Domains

   • Prerequisites: Generate the server certificates with the internal domain names and sign them using a trusted CA. Since the CA is trusted, there is no need to load the CA certificate in the target application.

   • Fault Configuration: Provide the base64-encoded server.key, server.crt, and any intermediate certificates in the SERVER_CERTIFICATES environment variable.

     cat server.key server.crt <intermediate-certificates> > server.pem
     cat server.pem | base64  # Add this to the SERVER_CERTIFICATES env

2. For External Domains

   • Prerequisites: Generate the server certificates that include both internal and external domain names, and sign them with the trusted CA. Since the CA is trusted, there is no need to load the CA certificates in the target application.

   • Fault Configuration: Provide the base64-encoded server.key, server.crt, and any intermediate certificates in the SERVER_CERTIFICATES environment variable.

     cat server.key server.crt <intermediate-certificates> > server.pem
     cat server.pem | base64  # Add this to the SERVER_CERTIFICATES env

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.
• NETWORK_INTERFACE: Network interface used for the proxy.

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

# it injects the api modify body 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-block
      spec:
        components:
          env:
            # provide the proxy port
            - name: PROXY_PORT
              value: '20000'
            # provide the connection type
            - name: SERVICE_DIRECTION
              value: 'ingress'
            # 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"

Advanced filters

• HEADERS_FILTERS: The HTTP request headers filters, that accept multiple comma-separated headers in the format of key1:value1,key2:value2.
• METHODS: The HTTP request method type filters, that accept comma-separated HTTP methods in upper case, that is, GET,POST.
• QUERY_PARAMS: The HTTP request query parameters filter, accepts multiple comma-separated query parameters in the format of param1:value1,param2:value2.
• SOURCE_HOSTS: Comma-separated source host names filters, indicating the origin of the HTTP request. This is relevant to the ingress type, specified by SERVICE_DIRECTION environment variable.
• SOURCE_IPS: Comma-separated source IPs filters, indicating the origin of the HTTP request. This is specifically relevant to the ingress type, specified by SERVICE_DIRECTION environment variable.
• DESTINATION_HOSTS: Comma-separated destination host names filters, indicating the hosts on which you call the API. This specification applies exclusively to the egress type, specified by SERVICE_DIRECTION environment variable.
• DESTINATION_IPS: Comma-separated destination IPs filters, indicating the hosts on which you call the API. This specification applies exclusively to the egress type, specified by SERVICE_DIRECTION environment variable.

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

# it injects the api block 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-block
      spec:
        components:
          env:
            # provide the headers filters
            - name: HEADERS_FILTERS
              value: 'key1:value1,key2:value2'
            # provide the methods filters
            - name: METHODS
              value: 'GET,POST'
            # provide the query params filters
            - name: QUERY_PARAMS
              value: 'param1:value1,param2:value2'
            # provide the source hosts filters
            - name: SOURCE_HOSTS
              value: 'host1,host2'
            # provide the source ips filters
            - name: SOURCE_IPS
              value: 'ip1,ip2'
            # provide the connection type
            - name: SERVICE_DIRECTION
              value: 'ingress'
            # provide the port of the targeted service
            - name: TARGET_SERVICE_PORT
              value: "80"

Container runtime and socket path

The CONTAINER_RUNTIME and SOCKET_PATH environment variables 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 the path as /var/run/docker.sock. For crio, specify the 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-block
      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'