# Chaos Monkey — Random Instance Failure Injection by Netflix

> Chaos Monkey randomly terminates virtual machine instances and containers in production to encourage engineers to build resilient services that tolerate unexpected failures.

## Install

Save as a script file and run:

# Chaos Monkey — Random Instance Failure Injection by Netflix

## Quick Use
```bash
# Clone and build
git clone https://github.com/Netflix/chaosmonkey.git
cd chaosmonkey
go build -o chaosmonkey ./cmd/chaosmonkey

# Configure with Spinnaker endpoint
export CHAOSMONKEY_ENABLED=true
./chaosmonkey migrate    # set up the MySQL schema
./chaosmonkey schedule   # enroll apps for termination
```

## Introduction
Chaos Monkey is a resiliency tool from Netflix that randomly terminates instances in production. It was born from the Simian Army philosophy: if your infrastructure cannot handle random failure gracefully, it is better to discover that during business hours than at 3 a.m.

## What Chaos Monkey Does
- Randomly terminates virtual machine instances or containers in a target environment
- Integrates with Spinnaker to discover applications and their server groups
- Allows per-app opt-in/opt-out through Spinnaker application properties
- Uses a configurable schedule and probability to control termination frequency
- Tracks termination events in a MySQL database for auditing

## Architecture Overview
Chaos Monkey is a standalone Go binary that talks to Spinnaker's REST API to enumerate applications, clusters, and server groups. On each scheduled run it selects eligible instances based on configurable mean-time-between-kills and grouping strategy, then calls Spinnaker to terminate the chosen instance. State and scheduling data persist in a MySQL backend.

## Self-Hosting & Configuration
- Requires a running Spinnaker deployment with Chaos Monkey support enabled
- MySQL 5.6+ stores termination schedules and event history
- Configuration lives in a TOML file specifying Spinnaker endpoint, database DSN, and schedule
- `chaosmonkey migrate` initializes or upgrades the database schema
- Environment-level toggles let you disable terminations without redeploying

## Key Features
- Battle-tested at Netflix scale across thousands of microservices
- Configurable mean-time-between-kills per application or cluster
- Grouping strategies: app, stack, or cluster granularity
- Dry-run mode logs what would be terminated without acting
- MySQL-backed audit trail of every termination event

## Comparison with Similar Tools
- **Chaos Mesh** — Kubernetes-native with network, I/O, and pod chaos; broader fault types but more complex setup
- **Litmus** — CNCF project offering experiment-as-code with a ChaosHub marketplace
- **ChaosBlade** — Alibaba's toolkit covering JVM, container, and network faults
- **Gremlin** — Commercial SaaS with managed chaos experiments and GameDay support
- **Pumba** — Docker-focused tool for container kill, pause, and network emulation

## FAQ
**Q: Does Chaos Monkey only work with AWS?**
A: It works with any cloud provider that Spinnaker supports, including GCP, Azure, and bare-metal Kubernetes.

**Q: Can I limit which apps are affected?**
A: Yes. Each Spinnaker application opts in or out, and you can set per-app probability and grouping.

**Q: Is a Spinnaker deployment mandatory?**
A: The open-source version requires Spinnaker for instance discovery and termination. Alternatives like Chaos Mesh or Litmus work without it.

**Q: How is Chaos Monkey different from the broader Simian Army?**
A: Simian Army was a collection of tools (Latency Monkey, Conformity Monkey, etc.). Chaos Monkey is the instance-termination component, and the only one Netflix open-sourced in Go.

## Sources
- https://github.com/Netflix/chaosmonkey
- https://netflix.github.io/chaosmonkey/

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Author: Script Depot