generators:
  - name: events
    config:
      interval: 1s
    value:
      eventId: =uuid()
      source: =oneOf(web, mobile, api)
      score: =uniform(0, 100, round=1)
      createdAt: =now(format=RFC3339Milli)

No connection yet — this file only describes the events. Values beginning with = are expressions that Synthtraffic calculates for each event. interval: 1s moves createdAt forward by one second each time.

The command below also asks sample for at most three events across the whole file.

3. Sample

sample requires the license configured in step 1. Pick CLI or Docker; the sample command prints preview events to your terminal.

Run the sample

Requires Install and License from step 1 (binary on PATH, SYNTHTRAFFIC_LICENSE_FILE set).

synthtraffic sample hello-world.yaml --events 3 --seed 42

Run the sample

Requires Install and License from step 1 (image pulled, --env-file on every run).

docker run --rm \
  --env-file ./license.env \
  --volume "${PWD}/hello-world.yaml:/work/hello-world.yaml:ro" \
  synthtraffic/synthtraffic:latest \
  sample /work/hello-world.yaml --events 3 --seed 42

--rmRemoves the stopped container after the sample finishes.

--env-filePasses license variables from license.env into the container.

--volumeMounts hello-world.yaml inside the container as a read-only file.

sample ...Prints three preview events to stdout.

4. What you should see

JSON Lines — one object per event. With --seed 42, the random fields match a second run. createdAt is started at current time and steps forward one second each line, so it changes on every run:

{"eventId":"a3e390d7-1f37-4053-88fb-d0a3c4728058","source":"mobile","score":95.7,"createdAt":"2026-01-02T03:04:05.000Z"}
{"eventId":"04c54733-c8e5-4a14-9f04-bd9c4607f04e","source":"mobile","score":53.5,"createdAt":"2026-01-02T03:04:06.000Z"}
{"eventId":"c47f2c8d-22e7-4a1d-b034-2479e6bb38ef","source":"web","score":81.0,"createdAt":"2026-01-02T03:04:07.000Z"}

You have a working preview. Choose one path:

Overview — from event shape to connections, with Try it beside the YAML
Scenario file — start the authoring path, one section at a time

Quickstart

1. Install and set a license

2. A tiny scenario

3. Sample

Run the sample

Run the sample

4. What you should see

Next