uukuguy Root Cause Analysis Skill
Objectives
Provide structured methodology for finding root causes:
- Move beyond symptoms to causes
- Identify systemic issues
- Prevent recurrence
- Document learnings
RCA Frameworks
5 Whys Analysis
Ask "Why?" iteratively until root cause found:
| Level | Question | Example |
|---|---|---|
| Why 1 | Why did it fail? | Test assertion failed |
| Why 2 | Why did assertion fail? | Wrong value returned |
| Why 3 | Why was value wrong? | Calculation error |
| Why 4 | Why was calculation wrong? | Variable not initialized |
| Why 5 | Why wasn't it initialized? | Missing init in constructor |
Root Cause: Constructor missing variable initialization
Fishbone (Ishikawa) Diagram
Categories for software bugs:
- Code: Logic errors, edge cases, algorithms
- Data: Invalid input, corrupt state, missing validation
- Environment: Config, dependencies, resources
- Integration: APIs, protocols, contracts
- Process: Testing gaps, review failures
Fault Tree Analysis
[Bug Symptom]
|
+-------------+-------------+
| | |
[Cause A] [Cause B] [Cause C]
| |
+----+----+ +----+----+
| | | |
[A1] [A2] [B1] [B2]
Investigation Phases
Phase 1: Problem Definition
- What is the symptom?
- When does it occur?
- What is the impact?
- Is it reproducible?
Phase 2: Data Collection
- Error messages and logs
- System state at failure
- Recent changes (code, config, deps)
- Related issues
Phase 3: Analysis
- Timeline reconstruction
- Cause-effect mapping
- Hypothesis testing
- Evidence evaluation
Phase 4: Solution
- Root cause identification
- Fix development
- Verification
- Prevention measures
Root Cause Categories
Immediate Causes
Direct trigger of the bug:
- Specific code line
- Particular input value
- Configuration setting
Contributing Causes
Factors that enabled the bug:
- Missing validation
- Insufficient testing
- Code complexity
Systemic Causes
Organizational/process issues:
- Missing code review
- Inadequate testing strategy
- Documentation gaps
Prevention Strategies
Technical Prevention
- Input validation
- Defensive programming
- Error handling
- Type checking
Process Prevention
- Code review checklists
- Testing requirements
- CI/CD gates
- Documentation standards
Monitoring Prevention
- Health checks
- Alerting thresholds
- Anomaly detection
- Audit logging
Output Template
# Root Cause Analysis Report
## Problem Statement
[Clear description of the bug]
## Timeline
- [Time]: [Event]
- [Time]: [Event]
## Investigation Summary
[What was investigated and found]
## Root Cause
**Immediate**: [Direct cause]
**Contributing**: [Enabling factors]
**Systemic**: [Process/org issues]
## Evidence
- [Evidence 1]
- [Evidence 2]
## Solution
**Fix**: [Technical solution]
**Verification**: [How to verify fix]
## Prevention
- [Prevention measure 1]
- [Prevention measure 2]
## Lessons Learned
- [Learning 1]
- [Learning 2]