═══════════════════════════════════════════════════════════════
A3 PROBLEM ANALYSIS
═══════════════════════════════════════════════════════════════
TITLE: API Downtime Due to Connection Pool Exhaustion
OWNER: Backend Team Lead
DATE: 2024-11-14
┌─────────────────────────────────────────────────────────────┐
│ 1. BACKGROUND │
├─────────────────────────────────────────────────────────────┤
│ • API goes down 2-3x per week during peak hours │
│ • Affects 10,000+ users, average 15min downtime │
│ • Revenue impact: ~$5K per incident │
│ • Customer satisfaction score dropped from 4.5 to 3.8 │
│ • Started 3 weeks ago after traffic increased 40% │
└─────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────┐
│ 2. CURRENT CONDITION │
├─────────────────────────────────────────────────────────────┤
│ Observations: │
│ • Connection pool size: 10 (unchanged since launch) │
│ • Peak concurrent users: 500 (was 300 three weeks ago) │
│ • Average request time: 200ms (was 150ms) │
│ • Connections leaked: ~2 per hour (never released) │
│ • Error: "Connection pool exhausted" in logs │
│ │
│ Pattern: │
│ • Occurs at 2pm-4pm daily (peak traffic) │
│ • Gradual degradation over 30 minutes │
│ • Recovery requires app restart │
│ • Long-running queries block pool (some 30+ seconds) │
└─────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────┐
│ 3. GOAL/TARGET │
├─────────────────────────────────────────────────────────────┤
│ • Zero downtime due to connection exhaustion │
│ • Support 1000 concurrent users (2x current peak) │
│ • All connections released within 5 seconds │
│ • Achieve within 1 week │
└─────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────┐
│ 4. ROOT CAUSE ANALYSIS │
├─────────────────────────────────────────────────────────────┤
│ 5 Whys: │
│ Problem: Connection pool exhausted │
│ Why 1: All 10 connections in use, none available │
│ Why 2: Connections not released after requests │
│ Why 3: Error handling doesn't close connections │
│ Why 4: Try-catch blocks missing .finally() │
│ Why 5: No code review checklist for resource cleanup │
│ │
│ Contributing factors: │
│ • Pool size too small for current load │
│ • No connection timeout configured (hangs forever) │
│ • Slow queries hold connections longer │
│ • No monitoring/alerting on pool metrics │
│ │
│ ROOT CAUSE: Systematic issue with resource cleanup + │
│ insufficient pool sizing │
└─────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────┐
│ 5. COUNTERMEASURES │
├─────────────────────────────────────────────────────────────┤
│ Immediate (This Week): │
│ 1. Audit all DB code, add .finally() for connection release │
│ 2. Increase pool size: 10 → 30 │
│ 3. Add connection timeout: 10 seconds │
│ 4. Add pool monitoring & alerts (>80% used) │
│ │
│ Short-term (2 Weeks): │
│ 5. Optimize slow queries (add indexes) │
│ 6. Implement connection pooling best practices doc │
│ 7. Add automated test for connection leaks │
│ │
│ Long-term (1 Month): │
│ 8. Migrate to connection pool library with auto-release │
│ 9. Add linter rule detecting missing .finally() │
│ 10. Create PR checklist for resource management │
└─────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────┐
│ 6. IMPLEMENTATION PLAN │
├─────────────────────────────────────────────────────────────┤
│ Week 1 (Nov 14-18): │
│ • Day 1-2: Audit & fix connection leaks [Dev Team] │
│ • Day 2: Increase pool size, add timeout [DevOps] │
│ • Day 3: Set up monitoring [SRE] │
│ • Day 4: Test under load [QA] │
│ • Day 5: Deploy to production [DevOps] │
│ │
│ Week 2 (Nov 21-25): │
│ • Optimize identified slow queries [DB Team] │
│ • Write best practices doc [Tech Writer + Dev Lead] │
│ • Create connection leak test [QA Team] │
│ │
│ Week 3-4 (Nov 28 - Dec 9): │
│ • Evaluate connection pool libraries [Dev Team] │
│ • Add linter rules [Dev Lead] │
│ • Update PR template [Dev Lead] │
│ │
│ Dependencies: None blocking Week 1 fixes │
│ Resources: 2 developers, 1 DevOps, 1 SRE │
└─────────────────────────────────────────────────────────────┘
┌─────────────────────────────────────────────────────────────┐
│ 7. FOLLOW-UP │
├─────────────────────────────────────────────────────────────┤
│ Success Metrics: │
│ • Zero downtime incidents (monitor 4 weeks) │
│ • Pool usage stays <80% during peak │
│ • No connection leaks detected │
│ • Response time <200ms p95 │
│ │
│ Monitoring: │
│ • Daily: Check pool usage dashboard │
│ • Weekly: Review connection leak alerts │
│ • Bi-weekly: Team retrospective on progress │
│ │
│ Review Dates: │
│ • Week 1 (Nov 18): Verify immediate fixes effective │
│ • Week 2 (Nov 25): Assess optimization impact │
│ • Week 4 (Dec 9): Final review, close A3 │
│ │
│ Prevention: │
│ • Add connection handling to onboarding │
│ • Monthly audit of resource management code │
│ • Include pool metrics in SRE runbook │
└─────────────────────────────────────────────────────────────┘
═══════════════════════════════════════════════════════════════