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SSH chaos

SSH chaos injects chaos on the target host using SSH connections by passing custom chaos logic through a ConfigMap. These scripts are executed using SSH credentials, which are securely referenced in the ConfigMap. This enables direct fault injection on the target host. This experiment offers customisation for the chaos injection logic, providing flexibility and control over chaos experiments.

SSH chaos

Use cases​

SSH chaos can be used with custom chaos logic and transferred to a target VM (to execute network chaos experiments, power off, and so on).

  • This serves as a framework that can be customised to perform other chaos experiments, such as network stress, HTTP, DNS, restart services, and so on.
  • This framework can be used to roll back to the original state of an abort event.

Executing the SSH chaos experiment​

Before executing the SSH chaos experiment, ensure that you follow the steps in the prerequisites section. This generates two experiment YAML files, namely ssh-chaos-with-key.yaml and ssh-chaos-with-pass.yaml. You can use one of them based on the authentication method you choose.

  • Use ssh-chaos-with-key.yaml for private key authentication. This file references secrets in its YAML view. The PASSWORD environment variable should be empty.

  • Use ssh-chaos-with-pass.yaml for password authentication. This file fetches the PASSWORD environment variable from the secret.

tip

If you use the default names for ConfigMap and secrets, you won't need to modify the experiment. If you use different names, update the respective environment variables with their names. For example, if your script file is test.sh instead of script.sh, update the CHAOS SCRIPT PATH environment variable with the correct value.

Mandatory tunables​

Variables Description Notes
HOST Name of the target host under chaos. Provide the name of the target host, for example, https://google.com.
USERNAME Username of the target VM. For example, "username".
PASSWORD Password used for authentication. Either PASSWORD or PRIVATE KEY is used. For example: "abcd".
PRIVATE KEY Key used for file-based authentication. Either PASSWORD or PRIVATE KEY is used. For example: key-file.pem
CHAOS SCRIPT PATH Path to the chaos script. For more information, go to chaos script path.
ABORT SCRIPT PATH Path to the abort script. For more information, go to abort script path.
CHAOS_PARAMETER Parameter for the chaos script. For more information, go to chaos parameter.
ABORT_PARAMETER Parameter for the abort script. For more information, go to abort parameter.
INDICATOR_TYPES Comma-separated indicator types for customisation of parameter indicators. For more information, go to indicator types.
note

HCE recommends using the format env:{$ENV_NAME} to pass confidential parameters. In this method, the environment variable is retrieved from a secure source (such as a secret). This ensures that the sensitive information remains uncompromised.

Chaos script path​

Path to the chaos script (the chaos script is used to create the ConfigMap). Tune it by using the CHAOS_SCRIPT_PATH environment variable.

The following YAML snippet illustrates the environment variable:

apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: load-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ssh-chaos
    spec:
      components:
        env:
        - name: CHAOS_SCRIPT_PATH
          value: /tmp/chaos-script/chaos-script.sh

Abort script path​

Path to the abort script (the abort script is used to create the ConfigMap). Tune it by using the ABORT_SCRIPT_PATH environment variable.

The following YAML snippet illustrates the environment variable:

apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: load-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ssh-chaos
    spec:
      components:
        env:
        - name: ABORT_SCRIPT_PATH
          value: /tmp/abort-script/abort-script.sh

Chaos parameter​

Parameter for the chaos script. Tune it by using the CHAOS_PARAMETER environment variable.

The following YAML snippet illustrates the environment variable:

apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: load-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ssh-chaos
    spec:
      components:
        env:
        - name: CHAOS_PARAMETER
          value: "{\"parameters\":[{\"placeholder\":\"destination_ip\",
                    \"data_type\":\"string\",\"value\":\"HOST_IP\"},
                    {\"placeholder\":\"port\",\"data_type\":\"int\",
                      \"value\":\"3258\"}]}"

Abort parameter​

Parameter for the abort script. Tune it by using the ABORT_PARAMETER environment variable.

The following YAML snippet illustrates the environment variable:

apiVersion: litmuschaos.io/v1alpha1
kind: ChaosEngine
metadata:
  name: load-nginx
spec:
  engineState: "active"
  chaosServiceAccount: litmus-admin
  experiments:
  - name: ssh-chaos
    spec:
      components:
        env:
        - name: ABORT_PARAMETER
          value: "{\"parameters\":[{\"placeholder\":\"destination_ip\",
                    \"data_type\":\"string\",\"value\":\"HOST_IP\"},
                    {\"placeholder\":\"port\",\"data_type\":\"int\",
                      \"value\":\"3258\"}]}"
tip

Input parameters can be specified in different formats.

  1. Raw value format: raw:{value}. Example:
- name: CHAOS_PARAMETER
   value: "raw:{value}"
  1. Environment variable format: env:{$ENV1}. Example:
- name: CHAOS_PARAMETER
   value: "env:{$ENV1}"
  1. Combination format: raw:{value},env:{$ENV1}. Example:
- name: CHAOS_PARAMETER
   value: "raw:{value},env:{$ENV1}"

Indicator types​

Comma-separated indicator types that allow for the customisation of parameter indicators. This customisation enhances the flexibility of parameter specification. Tune it by using the INDICATOR_TYPES environment variable. Customisable indicators include:

  1. raw: - String parameter
  2. env: - Environment variable parameter
  3. $ - Variable

Following are examples of default and customised formats:

  1. The default format is raw:{HCE,CSV},env:{$OPERATION},raw:{para3}.
  2. The customised format is string:{HCE,CSV},environment:{&OPERATION},raw:{para3}.

To implement a customised format, set the INDICATOR_TYPES to string,environment,&. This setting allows modifying the indicators for raw, environment, and $ values, thereby providing a tailored approach to parameter passing.

chaos parameters

Customising ConfigMap and Secret names​

SSH chaos is equipped to support custom names for ConfigMap and secrets by making a minor modification to the corresponding YAML file.

Suppose you wish to name the ConfigMap names as chaos-cm and abort-cm instead of the default chaos-script and abort-script, update the section below in the experiment builder:

configMaps:
  - name: chaos-script
    mountPath: /tmp/chaos-script
  - name: abort-script
    mountPath: /tmp/abort-script

to:

configMaps:
  - name: chaos-cm
    mountPath: /tmp/chaos-script
  - name: abort-cm
    mountPath: /tmp/abort-script

After you make the above changes, Save the updated file and Run the updated experiment.

Customizing environment variables​

If you wish to use the default ConfigMap and secret names but the script has a different name, you can update the environment variables (ENV) to align with the correct script by updating the script name in the chaos-script path or abort-script path.

customizing env var