# k6 Load Testing

Reproducible load test profile for `POST /api/v1/decide`.

## Prerequisites

- Docker + Docker Compose
- `jq`
- Running stack (`docker compose -f compose.yaml up -d`)

## One-command run

```bash
./infrastructure/k6/run-decide.sh
```

This command:

1. Prepares deterministic fixture via `prepare_k6_fixture`.
2. Runs `grafana/k6` in a pinned container image.
3. Saves artifacts to `artifacts/k6/<RUN_ID>/`.

Artifacts:

- `fixture.json`
- `run.env`
- `summary.json`

## Reproducible rerun

Use the same `RUN_ID` and k6 profile parameters.

```bash
RUN_ID=baseline_20260224 \
START_RPS=20 \
RAMP_UP_RPS=200 \
HOLD_RPS=200 \
HOLD_DURATION=2m \
./infrastructure/k6/run-decide.sh
```

## Target URL

Default target for k6 container:

- `K6_BASE_URL=http://host.docker.internal`

Override if needed:

```bash
K6_BASE_URL=http://host.docker.internal:14609 ./infrastructure/k6/run-decide.sh
```

## Profile knobs

- `START_RPS`
- `RAMP_UP_RPS`
- `HOLD_RPS`
- `RAMP_UP_DURATION`
- `HOLD_DURATION`
- `RAMP_DOWN_DURATION`
- `PRE_ALLOCATED_VUS`
- `MAX_VUS`
- `THRESHOLD_ERROR_RATE`
- `THRESHOLD_P95_MS`
- `THRESHOLD_P99_MS`
- `K6_IMAGE`

## Compare two runs

```bash
BASE=artifacts/k6/baseline_20260224/summary.json
CAND=artifacts/k6/candidate_20260224/summary.json

jq -n --argfile b "$BASE" --argfile c "$CAND" '{
  baseline_p95_ms: $b.metrics.http_req_duration["p(95)"],
  candidate_p95_ms: $c.metrics.http_req_duration["p(95)"],
  baseline_req_per_s: $b.metrics.http_reqs.rate,
  candidate_req_per_s: $c.metrics.http_reqs.rate,
  baseline_error_rate: $b.metrics.http_req_failed.value,
  candidate_error_rate: $c.metrics.http_req_failed.value
}'
```