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:

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]