Command probe

Command probe allows you to run Bash commands and match the output as a part of the entry or exit criteria. The intent behind this probe is to implement a non-standard and imperative way to express the hypothesis. For example, you can check for specific data within a database, parse the value out of a JSON blob that is dumped into a certain path, or check for the existence of a particular string in the service logs.

YAML only feature

By default, this probe can be defined in inline mode from the user interface, where the command is run from within the experiment image. It can also be run in source mode, where the command execution is carried out from within a new pod whose image is specified. Inline mode is preferred for simple shell commands, and source mode is preferred when application-specific binaries are required. For more information, go to probe schema.

Defining the probe

You can define the probe at .spec.experiments[].spec.probe path inside the chaos engine.

kind: Workflow
apiVersion: argoproj.io/v1alpha1
spec:
  templates:
    - inputs:
        artifacts:
          - raw:
              data: |
                apiVersion: litmuschaos.io/v1alpha1
                kind: ChaosEngine
                spec:
                  experiments:
                    - spec:
                        probe:
                          ####################################
                          Probes are defined here
                          ####################################

Schema

Listed below is the probe schema for the command probe with properties shared across all the probes and properties unique to the command probe.

Field	Description	Type	Range	Notes
name	Flag that holds the name of the probe	Mandatory	N/A `type: string`	The `name` holds the name of the probe. Set based on the use case.
type	Flag to hold the type of the probe	Mandatory	`httpProbe, k8sProbe, cmdProbe, promProbe`	The `type` supports four types of probes. It can one of the httpProbe, k8sProbe, cmdProbe, promProbe
mode	Flag to hold the mode of the probe	Mandatory	`SOT, EOT, Edge, Continuous, OnChaos`	The `mode` supports five modes of probes. It can one of the SOT, EOT, Edge, Continuous, OnChaos
command	Flag to hold the command for the cmdProbe	Mandatory	N/A `type: string`	The `command` contains the shell command, which should be run as part of cmdProbe
insecureSkipVerify	Flag to hold the flag to skip certificate checks for the httpProbe	Optional	true, false	The `insecureSkipVerify` contains flag to skip certificate checks.
responseTimeout	Flag to hold the flag to response timeout for the httpProbe	Optional	N/A `type: integer`	The `responseTimeout` contains flag to provide the response timeout for the http Get/Post request.

Source

Field	Description	Type	Range	Notes
image	Flag to hold the image for the cmdProbe	Optional	any source docker image	The `image` provides the source image which can be used to launch a external pod where the command execution is carried out.
hostNetwork	Description Flag to allow or deny the `image` access to the node network namespace	Optional	`true, false`	The `hostNetwork` provides a possibility to allow the pod executing the cmdProbe access to the network of the node he is running on. For more details, go to the offical Kubernetes documentation.

Comparator

Field	Description	Type	Range	Notes
type	Flag to hold type of the data used for comparision	Mandatory	`string, int, float`	The `type` contains type of data, which should be compare as part of comparision operation.
criteria	Flag to hold criteria for the comparision	Mandatory	it supports `>=, <=, ==, >, <, !=, oneOf, between` for int & float type. And `equal, notEqual, contains, matches, notMatches, oneOf` for string type.	The `criteria` contains criteria of the comparision, which should be fulfill as part of comparision operation.
value	Flag to hold value for the comparision	Mandatory	N/A `type: string`	The `value` contains value of the comparision, which should follow the given criteria as part of comparision operation.

Run properties

Field	Description	Type	Range	Notes
probeTimeout	Flag to hold the timeout of the probe	Mandatory	N/A `type: integer`	The `probeTimeout` represents the time limit for the probe to execute the specified check and return the expected data
retry	Flag to hold the retry count of the probe	Mandatory	N/A `type: integer`	The `retry` contains the number of times a check is re-run upon failure in the first attempt before declaring the probe status as failed.
interval	Flag to hold the interval of the probe	Mandatory	N/A `type: integer`	The `interval` contains the interval for which probes waits between subsequent retries
probePollingInterval	Flag to hold the polling interval for the probes (applicable for all modes)	Optional	N/A `type: integer`	The `probePollingInterval` contains the time interval for which continuous probe should be sleep after each iteration
initialDelaySeconds	Flag to hold the initial delay interval for the probes	Optional	N/A `type: integer`	The `initialDelaySeconds` represents the initial waiting time interval for the probes.
stopOnFailure	Flags to hold the stop or continue the experiment on probe failure	Optional	N/A `type: boolean`	The `stopOnFailure` can be set to true/false to stop or continue the experiment execution after probe fails

Definition

probe:
  - name: "check-database-integrity"
    type: "cmdProbe"
    cmdProbe/inputs:
      command: "<command>"
      comparator:
        type: "string" # supports: string, int, float
        criteria: "contains" #supports >=,<=,>,<,==,!= for int and contains,equal,notEqual,matches,notMatches for string values
        value: "<value-for-criteria-match>"
      source: # omit this tag to "inline" the probe
        image: "<repo>/<tag>"
        hostNetwork: false
    mode: "Edge"
    runProperties:
      probeTimeout: 5
      interval: 5
      retry: 1
      initialDelaySeconds: 5

Defining the probe​

Schema​

Source​

Comparator​

Run properties​

Definition​