genx

genx is a lightweight time-series data generator. It emits synthetic measurements following a mathematical curve — useful for testing dashboards, messaging pipelines, or IoT simulators.

Each data point is output as JSON:

{"device":"sensor1","timestamp":1715000000,"value":24.53}

Quick start

docker run ghcr.io/lucj/genx [flags]

Or build locally:

go build -o genx . && ./genx [flags]

Curve types

Cosine

Oscillates between --min and --max over the given --period.

$ docker run ghcr.io/lucj/genx -type cos -duration 2d -min 20 -max 30 -step 3h -period 1d
{"device":"device","timestamp":1715000000,"value":30.00}
{"device":"device","timestamp":1715010800,"value":27.50}
{"device":"device","timestamp":1715021600,"value":22.50}
{"device":"device","timestamp":1715032400,"value":20.00}
...

Linear

Ramps from --first to --last over the total duration.

$ docker run ghcr.io/lucj/genx -type linear -duration 3d -first 10 -last 30 -step 6h
{"device":"device","timestamp":1715000000,"value":10.00}
{"device":"device","timestamp":1715021600,"value":11.67}
{"device":"device","timestamp":1715043200,"value":13.33}
...

Logarithmic

Produces a slow-growing logarithmic curve (natural log of elapsed seconds).

$ docker run ghcr.io/lucj/genx -type log -duration 1d -step 2h
{"device":"device","timestamp":1715000000,"value":0.00}
{"device":"device","timestamp":1715007200,"value":8.88}
{"device":"device","timestamp":1715014400,"value":9.57}
...

Exponential

Grows exponentially over the duration.

$ docker run ghcr.io/lucj/genx -type exp -duration 6h -step 30m
{"device":"device","timestamp":1715000000,"value":1.00}
{"device":"device","timestamp":1715001800,"value":1.07}
{"device":"device","timestamp":1715003600,"value":1.15}
...

Output sinks

By default data is written to stdout. Use --output to route it elsewhere.

Webhook

POSTs each data point as JSON to an HTTP endpoint.

$ docker run ghcr.io/lucj/genx -type cos -duration 1h -step 5m \
    -output webhook -webhook-url http://myserver/ingest

NATS

Publishes to a NATS subject.

$ docker run ghcr.io/lucj/genx -type linear -duration 1h -step 1m \
    -output nats -nats-url nats://<NATS_HOST>:4222 -nats-subject sensors.temp

End-to-end example with a containerised NATS server:

# 1. shared network
docker network create genx-net

# 2. NATS server
docker run -d --name nats --network genx-net nats

# 3. subscriber (another terminal)
docker run --rm --network genx-net natsio/nats-box \
    nats sub -s nats://nats:4222 sensors.temp

# 4. generate and publish
docker run --network genx-net ghcr.io/lucj/genx \
    -type linear -duration 1h -step 1m \
    -output nats -nats-url nats://nats:4222 -nats-subject sensors.temp

MQTT

Publishes to an MQTT topic.

$ docker run ghcr.io/lucj/genx -type cos -duration 1h -step 5m \
    -output mqtt -mqtt-broker tcp://<MQTT_HOST>:1883 -mqtt-topic home/temperature

Realtime mode

By default genx generates the full dataset instantly (batch mode). Add --realtime to emit one point per --step interval using the actual wall clock — handy for live pipeline testing.

$ docker run ghcr.io/lucj/genx -type cos -min 18 -max 26 -duration 1h -step 10s --realtime

All flags

Flag	Default	Description
-type	cos	Curve type: cos, linear, log, exp
-duration	1d	Total duration (e.g. 2d, 6h, 30m)
-step	1h	Sampling interval (e.g. 5m, 10s)
-device	device	Device/sensor name in each data point
-realtime	false	Emit one point per step using real time
-min	10	Min value (cos)
-max	25	Max value (cos)
-period	1d	Period (cos)
-first	0	First value (linear)
-last	1	Last value (linear)
-output	stdout	Output sink: stdout, webhook, nats, mqtt
-webhook-url		Webhook endpoint URL
-nats-url	nats://<NATS_HOST>:4222	NATS server URL
-nats-subject	genx	NATS subject
-mqtt-broker	tcp://<MQTT_HOST>:1883	MQTT broker URL
-mqtt-topic	genx	MQTT topic
-mqtt-qos	0	MQTT QoS level (0, 1, 2)
-mqtt-client-id	genx-<pid>	MQTT client ID