Chaos Squirrel

JavaScript Chaos

Packages

• Runner - Determine which attacks to run, and run them
• Wrapper Runner - Integrate the Chaos Runner into any function
• Middy Runner - Easily run attacks on Lambdas using Middy

Attacks

• CPU - In-process CPU exhaustion
• Background CPU - Spawn processes which exhaust CPU
• Open Files - Open lots of file descriptors to exhaust ulimit nofile
• Memory - Use lots of memory
• Background Memory - Use lots of memory in a forked process
• Disk Space - Consume lots of disk space
• Throw Error - Throws error or causes uncaught exception

Usage via Runner

import ChaosRunner from '@dazn/chaos-squirrel-runner';
import CPUAttack from '@dazn/chaos-squirrel-attack-cpu';
// in ES5/CommonJS
// const { default: CPUAttack } = require('@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
        // using a plain object will result in the attack name being "Object"
        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