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Customizing Kallisti

Parts of Kallisti are customizable to provide more flexibility in targeting different types of platforms for chaos testing. There are also some observers and hooks useful for things like usage analytics or any other custom events.

Authentication and Permission

Please refer to access control page.

Database

Kallisti uses Django Rest Framework internally for REST API portion. Therefore it is fairly straightforward to switch the database to other RDBMS. By default the database is SQLite specified in settings.py. Please refer to Django documentation for the details of databases and models.

Chaos Module Map

Kallisti comes with a mapping of chaos injection modules and it is customizable, which allows us to add custom chaos injection modules for our own needs such as the chaos injection to internally managed services.

The default mapping is as below. The keys are the module names and the values are the Python module paths. This map can be edited to enable custom modules.

kallisticore/config/settings.py

KALLISTI_MODULE_MAP = {
    'cf': 'kallisticore.modules.cloud_foundry',
    'cm': 'kallisticore.modules.common',
    'k8s': 'kallisticore.modules.kubernetes',
    'istio': 'kallisticore.modules.kubernetes',
    'prom': 'kallisticore.modules.prometheus',
    'aws': 'kallisticore.modules.aws'
}

The mechanism for the chaos injection modules to be loaded and for the actions to be executed is as below. Please refer to kallisticore/lib/action.py for the source code.

  • A chaos injection module is loadable as a Python module in the Python environment in use.
  • The action function is exported with __all__ list in the module.
  • If an action function exists in the dependency of a module, declaring its module path in __actions_modules__ list would expand the modules to be searched for the function.
  • By default, a step is mapped to the action function as follows:
    • key-value pairs in where clause of a step would be passed to an action function as arguments
    • credentials block of a step would be processed and passed to the action function as a Credential class
  • If additional processing of parameters is required, __action_class__ can be defined in the __init__.py of a module and custom Action class can be specified there. (see kallisticore/modules/prometheus/__init__.py as an example.)

Credential Handlers for Chaos Steps

Kallisti comes with a mapping of credential handlers for the chaos injection steps and it is customizable, which allows us to add custom credential handlers for our own needs such as the internally-managed identity providers or vault systems.

The default mapping is as below. The keys are the credential type and the values are the Python class path. This map can be edited to enable custom credential handlers.

kallisticore/config/settings.py

KALLISTI_CREDENTIAL_CLASS_MAP = {
    'ENV_VAR_USERNAME_PASSWORD': 'kallisticore.lib.credential.'
                                 'EnvironmentUserNamePasswordCredential',
    'TOKEN_FILE': 'kallisticore.lib.credential.TokenFileCredential',
    'K8S_SVC_ACC_TOKEN_FILE': 'kallisticore.lib.credential.'
                              'KubernetesServiceAccountTokenCredential'
}

Custom credential handlers should implement Credential base class in kallisticore/lib/credential.py.

Trial Observer

When one or more custom events are desired to be generated upon the completion of chaos trials, the trial observer can be used in Kallisti.

To enable the custom trial observers, TRIAL_OBSERVERS variable in settings.py can be used.

kallisti/config/settings.py

import MyCustomObserver
#...
# Custom trial observer classes to be executed at trial completion
# They need to implement kallisticore.lib.observe.observer.Observer
TRIAL_OBSERVERS = [MyCustomObserver]

As the comment in the above snippet states, custom observers must implement the Observer class in kalllisticore/lib/observe/observer.py.

Trial Creation Hook

When one or more custom events are desired to be generated upon the creation of chaos trials before its execution, the trial creation hook can be used in Kallisti. The hook functions will take a created trial object as a parameter, so they can be used to tweak the property of the trial before the execution.

To enable the custom hook upon the creation of trials, TRIAL_TASK_CREATION_HOOKS variable in settings.py can be used.

from my_custom_module import my_hook_func
# Custom trial creation hook functions to be executed at trial creation
TRIAL_TASK_CREATION_HOOKS = [
    # add_token_to_task etc...
    my_hook_func
]