performance-testing

# Performance Testing Load testing, web performance auditing, profiling, and benchmarking. ## Load Testing with k6 ### Quick smoke test ```bash k6 run --vus 1 --duration 10s script.js ``` ### Stress test ```bash k6 run --vus 100 --duration 5m script.js ``` ### Inline script (no file needed) ```bash k6 run -e URL=https://api.example.com - <<'EOF' import http from 'k6/http'; import { check, sleep } from 'k6'; export const options = { stages: [ { duration: '30s', target: 10 }, { duration: '1m', target: 50 }, { duration: '30s', target: 0 }, ], thresholds: { http_req_duration: ['p(95)<500'], http_req_failed: ['rate<0.01'], }, }; export default function () { const res = http.get(__ENV.URL); check(res, { 'status is 200': (r) => r.status === 200, 'response time < 500ms': (r) => r.timings.duration < 500, }); sleep(1); } EOF ``` ### k6 with JSON output ```bash k6 run --out json=results.json script.js cat results.json | jq 'select(.type=="Point" and .metric=="http_req_duration") | .data.value' | sort -n | tail -5 ``` ## Web Performance (Lighthouse) ### CLI audit ```bash # Full audit lighthouse https://example.com --output json --output html --output-path ./report # Performance only lighthouse https://example.com --only-categories=performance --output json | jq '{performance: .categories.performance.score, fcp: .audits["first-contentful-paint"].displayValue, lcp: .audits["largest-contentful-paint"].displayValue, cls: .audits["cumulative-layout-shift"].displayValue, tbt: .audits["total-blocking-time"].displayValue}' # Mobile simulation (default) lighthouse https://example.com --preset=perf --output json | jq '.categories.performance.score' # Desktop lighthouse https://example.com --preset=desktop --output json | jq '.categories.performance.score' ``` ### Core Web Vitals extraction ```bash lighthouse https://example.com --output json | jq '{ LCP: .audits["largest-contentful-paint"].numericValue, FID: .audits["max-potential-fid"].numericValue, CLS: .audits["cumulative-layout-shift"].numericValue, FCP: .audits["first-contentful-paint"].numericValue, TBT: .audits["total-blocking-time"].numericValue, SI: .audits["speed-index"].numericValue }' ``` ## HTTP Benchmarking ### curl timing ```bash # Detailed timing for single request curl -s -o /dev/null -w "DNS: %{time_namelookup}s\nConnect: %{time_connect}s\nTLS: %{time_appconnect}s\nTTFB: %{time_starttransfer}s\nTotal: %{time_total}s\nSize: %{size_download} bytes\n" https://example.com # Repeated measurements for i in $(seq 1 10); do curl -s -o /dev/null -w "%{time_total}" https://example.com echo "" done | awk '{sum+=$1; count++} END {print "Avg: " sum/count "s over " count " requests"}' ``` ### Apache Bench (ab) ```bash # 100 requests, 10 concurrent ab -n 100 -c 10 https://example.com/ # With POST data ab -n 100 -c 10 -p payload.json -T application/json https://api.example.com/endpoint ``` ## Bundle Size Analysis ```bash # Node.js bundle (webpack) npx webpack --profile --json > stats.json npx webpack-bundle-analyzer stats.json # Vite npx vite build --report # Package size check npx bundlephobia <package-name> # Check what you're shipping du -sh dist/ find dist/ -name "*.js" -exec du -sh {} \; | sort -rh | head -10 ``` ## Memory & CPU Profiling ```bash # Node.js heap snapshot node --inspect app.js # Then open chrome://inspect in Chrome # Node.js CPU profile node --cpu-prof app.js # Generates .cpuprofile file — open in Chrome DevTools # Python profiling python -m cProfile -s cumulative app.py | head -30 # Go profiling go test -bench=. -cpuprofile=cpu.prof -memprofile=mem.prof go tool pprof cpu.prof ``` ## Notes - k6 `p(95)<500` means 95th percentile response time under 500ms — a good baseline. - Lighthouse scores vary between runs. Run 3-5 times and average. - Always load test against staging, not production, unless you have explicit approval. - Bundle size directly impacts page load. Track it in CI. - Profile in production-like environments — dev mode adds overhead that skews results.