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Extension chaosaddons

Version 0.4.0
Repository https://github.com/chaostoolkit/chaostoolkit-addons

This project provides a set of commnly requested actions, probes, tolerances or controls that can benefit the community.

Install

This package requires Python 3.7+

To be used from your experiment, this package must be installed in the Python environment where chaostoolkit already lives.

$ pip install chaostoolkit-addons

Develop

Test

To run the tests for the project execute the following:

$ pytest

Contribute

If you wish to contribute more functions to this package, you are more than welcome to do so. Please, fork this project, make your changes following the usual PEP 8 code style, sprinkling with tests and submit a PR for review.

Exported Controls

bypass

Sets the dry property on activities that match either by type or by names.

This allows to bypass some activities in certain contexts. For instance, you want to run on development but not in production certain actions.

For instance, to bypass the execution of the say-hello activity:

"controls": [
        {
            "name": "bypass-actions",
            "provider": {
                "type": "python",
                "module": "chaosaddons.controls.bypass",
                "arguments": {
                    "target_names": [
                        "say-hello"
                    ]
                }
            }
        }
    ],

For instance, to bypass the execution of all actions in the experiment:

"controls": [
        {
            "name": "bypass-actions",
            "provider": {
                "type": "python",
                "module": "chaosaddons.controls.bypass",
                "arguments": {
                    "target_type": "action"
                }
            }
        }
    ],

This module exports controls covering the following phases of the execution of an experiment:

Level Before After
Experiment Loading False False
Experiment True False
Steady-state Hypothesis False False
Method False False
Rollback False False
Activities True True

In addition, the controls may define the followings:

Level Enabled
Validate Control False
Configure Control False
Cleanup Control False

To use this control module, please add the following section to your experiment:

{
  "controls": [
    {
      "name": "chaosaddons",
      "provider": {
        "type": "python",
        "module": "chaosaddons.controls.bypass"
      }
    }
  ]
}
controls:
- name: chaosaddons
  provider:
    module: chaosaddons.controls.bypass
    type: python

This block may also be enabled at any other level (steady-state hypothesis or activity) to focus only on that level.

When enabled at the experiment level, by default, all sub-levels are also applied unless you set the automatic properties to false.

repeat

This module exports controls covering the following phases of the execution of an experiment:

Level Before After
Experiment Loading False False
Experiment False False
Steady-state Hypothesis False False
Method False False
Rollback False False
Activities False True

In addition, the controls may define the followings:

Level Enabled
Validate Control False
Configure Control False
Cleanup Control False

To use this control module, please add the following section to your experiment:

{
  "controls": [
    {
      "name": "chaosaddons",
      "provider": {
        "type": "python",
        "module": "chaosaddons.controls.repeat"
      }
    }
  ]
}
controls:
- name: chaosaddons
  provider:
    module: chaosaddons.controls.repeat
    type: python

This block may also be enabled at any other level (steady-state hypothesis or activity) to focus only on that level.

When enabled at the experiment level, by default, all sub-levels are also applied unless you set the automatic properties to false.

safeguards

The safeguard control provides a mechanism to keep an eye on the system while running an experiment to decide if the experiment ought to stop as soon as possible or not.

For instance, let’s say your system detects a dire condition that has nothing to do with this experiment. It may decide it’s time for the experiment to terminate as it could create even more noise or problems.

To use this control, simply add the following to your global (or per experiment) controls block:

"controls": [
    {
        "name": "safeguard",
        "provider": {
            "type": "python",
            "module": "chaosaddons.controls.safeguards",
            "arguments": {
                "probes": [
                    {
                        "name": "safeguard_1",
                        "type": "probe",
                        "provider": {
                            "type": "python",
                            "module": "mymodule",
                            "func": "checkstuff"
                        },
                        "background": true,
                        "tolerance": true
                    },
                    {
                        "name": "safeguard_2",
                        "type": "probe",
                        "provider": {
                            "type": "python",
                            "module": "mymodule",
                            "func": "checkstuff"
                        },
                        "tolerance": true
                    },
                    {
                        "name": "safeguard_3",
                        "type": "probe",
                        "provider": {
                            "type": "python",
                            "module": "mymodule",
                            "func": "checkstuff"
                        },
                        "frequency": 2,
                        "tolerance": true
                    }
                ]
            }
        }
    }
],

In this example, we declare three safeguard probes. The first one will run once in the background as soon as possible. The second one will run once before the experiment starts. The third one will run repeatedly every 2 seconds.

If either of them doesn’t meet its tolerance, the entire execution will terminate as soon as possible and leave the status of the experiment to interrupted.

Probes that do not declare the background or frequency properties are meant to run before the experiment really starts and will block until they are all finished. This offers a mechanism for pre-checking the system’s health.

When the properties are set, the probes run as soon as possible but do not block the experiment from carrying on.

Bear in mind that your probes can also block the process from exiting. This means that while the experiment has ended, your probe could be not returning and therefore blocking the process. Make sure your probe do not make blocking calls for too long.

This module exports controls covering the following phases of the execution of an experiment:

Level Before After
Experiment Loading False False
Experiment True True
Steady-state Hypothesis False False
Method False False
Rollback False False
Activities False False

In addition, the controls may define the followings:

Level Enabled
Validate Control True
Configure Control True
Cleanup Control False

To use this control module, please add the following section to your experiment:

{
  "controls": [
    {
      "name": "chaosaddons",
      "provider": {
        "type": "python",
        "module": "chaosaddons.controls.safeguards"
      }
    }
  ]
}
controls:
- name: chaosaddons
  provider:
    module: chaosaddons.controls.safeguards
    type: python

This block may also be enabled at any other level (steady-state hypothesis or activity) to focus only on that level.

When enabled at the experiment level, by default, all sub-levels are also applied unless you set the automatic properties to false.

synchronization

This module exports controls covering the following phases of the execution of an experiment:

Level Before After
Experiment Loading False False
Experiment False True
Steady-state Hypothesis False False
Method False False
Rollback False False
Activities False False

In addition, the controls may define the followings:

Level Enabled
Validate Control False
Configure Control False
Cleanup Control False

To use this control module, please add the following section to your experiment:

{
  "controls": [
    {
      "name": "chaosaddons",
      "provider": {
        "type": "python",
        "module": "chaosaddons.controls.synchronization"
      }
    }
  ]
}
controls:
- name: chaosaddons
  provider:
    module: chaosaddons.controls.synchronization
    type: python

This block may also be enabled at any other level (steady-state hypothesis or activity) to focus only on that level.

When enabled at the experiment level, by default, all sub-levels are also applied unless you set the automatic properties to false.

Exported Activities

controls

utils


idle_for

Type
Module chaosaddons.utils.idle
Name idle_for
Return null

Pauses the experiment without blocking the process completely.

Signature:

def idle_for(duration: float) -> None:
    pass

Arguments:

Name Type Default Required
duration number Yes

Usage:

{
  "name": "idle-for",
  "type": "",
  "provider": {
    "type": "python",
    "module": "chaosaddons.utils.idle",
    "func": "idle_for",
    "arguments": {
      "duration": null
    }
  }
}
name: idle-for
provider:
  arguments:
    duration: null
  func: idle_for
  module: chaosaddons.utils.idle
  type: python
type: ''