Node not required (k6 runs standalone)
k6 installed (>= v0.43 recommended)
Prometheus + Grafana (optional) if you want to correlate with the dashboard you generated
A running cart service exposing HTTP endpoints at (default) http://localhost:8080/cart

Endpoints Exercised

The script exercises (per iteration):

GET /cart – ensure / fetch cart state (creates cart if missing; sets cartid & cartowner cookies)
POST /cart – add item mutation (random SKU & quantity)
GET /cart – fetch after mutations
GET /checkout – occasionally (~2% of iterations) to simulate checkout start

You can extend it easily to hit deliveries, quantity changes, or removal endpoints.

Environment Variables

Variable	Purpose	Default
`BASE_URL`	Base URL root (either host or host/cart)	`http://localhost:8080/cart`
`VUS`	VUs for steady_mutations scenario	`20`
`DURATION`	Duration for steady_mutations scenario	`5m`
`RAMP_TARGET`	Peak VUs for ramp_up scenario	`50`

You can also disable one scenario by editing options.scenarios inside the script.

Example run:

k6 run \
  -e BASE_URL=https://cart.k6n.net/cart \
  -e VUS=40 \
  -e DURATION=1m \
  -e RAMP_TARGET=120 \
  k6/cart_load_test.js

Metrics (Custom)

The script defines additional k6 metrics:

cart_add_item_duration (Trend) – latency of POST add item
cart_fetch_duration (Trend) – latency of GET cart state
cart_checkout_duration (Trend) – latency of checkout
cart_items_added (Counter) – successful add item operations
cart_checkout_calls (Counter) – successful checkout calls

Thresholds (in options.thresholds) enforce basic SLO:

Mutation failure rate < 2%
p90 mutation latency < 800 ms
p99 overall HTTP latency < 1500 ms

Adjust thresholds to your environment if they trigger prematurely.

Cookies & Stickiness

The script preserves:

cartid – cart identity (server sets expiry separately)
cartowner – owning host for sticky routing

If your load balancer or ingress enforces affinity based on these cookies, traffic will naturally concentrate on the originally claimed host for each cart under test.

SKU Set

SKUs used (randomly selected each mutation):

778290 778345 778317 778277 778267 778376 778244 778384
778365 778377 778255 778286 778246 778270 778266 778285
778329 778425 778407 778418 778430 778469 778358 778351
778319 778307 778278 778251 778253 778261 778263 778273
778281 778294 778297 778302

To add/remove SKUs, edit the SKUS array. Keeping it non-empty and moderately sized helps randomization.

Extending the Script

Add Quantity Change

function changeQuantity(itemId, newQty) {
  const payload = JSON.stringify({ Id: itemId, Qty: newQty });
  http.put(baseUrl() + '/', payload, { headers: headers() });
}

Remove Item

function removeItem(itemId) {
  http.del(baseUrl() + '/' + itemId, null, { headers: headers() });
}

Add Delivery

function addDelivery(itemIds) {
  const payload = JSON.stringify({ provider: "POSTNORD", items: itemIds });
  http.post(baseUrl() + '/delivery', payload, { headers: headers() });
}

You can integrate these into the iteration loop with probabilities.

Output Summary

handleSummary outputs a JSON summary to stdout:

Average & p95 mutation latencies (if present)
Fetch p95
Checkout count
Check statuses

Redirect or parse that output for CI pipelines.

Running in CI

Use shorter durations (e.g. DURATION=2m VUS=10) to keep builds fast. Fail build on threshold breaches:

k6 run -e BASE_URL=$TARGET -e VUS=10 -e DURATION=2m k6/cart_load_test.js || exit 1

Correlating with Prometheus / Grafana

During load, observe:

cart_mutations_total growth and latency histograms
Event log write rate (cart_event_log_appends_total)
Pool usage (cart_grain_pool_usage) and spawn rate (cart_grain_spawned_total)
Failure counters (cart_mutation_failures_total) ensure they remain low

If mutation latency spikes without high error rate, inspect external dependencies (e.g., product fetcher or Klarna endpoints).

Common Tuning Tips

Symptom	Potential Adjustment
High latency p99	Increase CPU/memory, optimize mutation handlers
Pool at capacity	Raise pool size argument or TTL
Frequent cart eviction mid-test	Confirm TTL is sliding (now 2h on mutation)
High replay duration	Consider snapshot + truncate event logs
Uneven host load	Verify `cartowner` cookie is respected upstream

Safety / Load Guardrails

Start with low VUs (5–10) and short duration.
Scale incrementally to find saturation points.
If using production endpoints, coordinate off-peak runs.

License / Attribution

This test script is tailored for your internal cart actor system; adapt freely. k6 is open-source (AGPL v3). Ensure compliance if redistributing.

Feel free to request:

A variant script for spike tests
WebSocket / long poll integration (if added later)
Synthetic error injection harness

Happy load testing!

README.md Unescape Escape

k6 Load Tests for Cart API

Contents

Prerequisites