name: chaos-engineering description: Test system resilience through controlled failures. Use when validating fault tolerance, disaster recovery, or system reliability. Covers chaos experiments. allowed-tools: Read, Write, Bash, Glob, Grep

Chaos Engineering

Principles

1. Build a Hypothesis: Define expected behavior
2. Minimize Blast Radius: Start small
3. Run in Production: Real conditions matter
4. Automate: Make experiments repeatable
5. Minimize Impact: Have abort conditions

Experiment Process

1. Steady State: Define normal metrics
2. Hypothesis: "System will maintain X under condition Y"
3. Introduce Variables: Inject failure
4. Observe: Compare to steady state
5. Analyze: Confirm or disprove hypothesis

Common Experiments

Network Failures

# Add latency
tc qdisc add dev eth0 root netem delay 100ms

# Packet loss
tc qdisc add dev eth0 root netem loss 10%

# Remove
tc qdisc del dev eth0 root

Resource Exhaustion

# CPU stress
stress --cpu 4 --timeout 60s

# Memory stress
stress --vm 2 --vm-bytes 1G --timeout 60s

# Disk fill
dd if=/dev/zero of=/tmp/fill bs=1M count=1024

Service Failures

• Kill processes
• Restart containers
• Terminate instances
• Block dependencies

Chaos Tools

• Chaos Monkey: Random instance termination
• Gremlin: Comprehensive chaos platform
• Litmus: Kubernetes chaos engineering
• Chaos Mesh: Cloud-native chaos

Experiment Template

## Experiment: [Name]

### Hypothesis
If [condition], then [expected behavior].

### Steady State
- Metric A: [baseline value]
- Metric B: [baseline value]

### Method
1. [Step 1]
2. [Step 2]
3. [Step 3]

### Abort Conditions
- If [condition], stop immediately

### Results
[What happened]

### Findings
[What we learned]

Safety Rules

1. Start in non-production
2. Have rollback ready
3. Monitor continuously
4. Communicate with team
5. Document everything