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

code

                    [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

markdown

# 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]