@dazn/chaos-squirrel-runner

Run chaos attacks!

Usage

import ChaosRunner from '@dazn/chaos-squirrel-runner';
import CPUAttack from '@dazn/chaos-squirrel-attack-cpu';

const createRunner = ChaosRunner.configure({
  probability: 1,
  possibleAttacks: [
    {
      weight: 2, // run twice as often as the default
      createAttack: CPUAttack.configure({ allowLoopEvery: 10 }),
    },
    {
      // weight: 1, // default value
      createAttack: () => {
        // Use a class for Attacks, as the Runner will take the class name as the attack name
        class CustomAttack {
          start() {
            // do a custom attack!
          }
          stop() {
            // stop the attack
          }
        }
        return new CustomAttack();
      },
    },
  ],

  // OPTIONAL: define a custom logger, defaults to console methods
  logger: (level, message, details) => console[level](message, details),
});

// a new instance of the runner should be created for each possible chaos run
const runner = createRunner();

// start the chaos!
runner.start();
// do things

// stop the chaos
runner.stop();

Runner Arguments

| Parameter | Type | Default | Description | | ----------------- | ---------- | --------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------- | | probability | Number | 1 | A "global" probability range between 0-1. Defaults to 1 which is 100% probability. | | possibleAttacks | Array | - | An array of objects of possible attacks that could be initiated | | logger | Function | (level, ...args) => console[level](...args) | A logger function which is called for significant actions/decisions, such as starting an attack. Set to a no-op (() => {}) to disable logging |

Possible Attack

| Parameter | Type | Default | Description | | -------------- | ---------- | ------- | --------------------------------------------------------------------------------------------------- | | weight | Number | 1 | Sets the weighting of an attack vs the other attacks. Default = 1, set to 0 to disable this attack. | | createAttack | Function | - | Function which returns an attack class exposing a start and stop method. |

Probabilities

The likelihood of running a given attack is the runner.probability * possibleAttack.weight / SUM(possibleAttacks.weight).

For example, if runner.probability is set to 0.5 and there are two possible attacks:

• Attack 1: weight = 1
• Attack 2: weight = 3

The probability of any each attack running will be

• Attack 1: 0.5 * 1 / 4 = 0.125
• Attack 2: 0.5 * 3 / 4 = 0.375
• Total probability (chances of either attack running) = runner.probability = 0.5