Friday, September 21, 2018

Fire-and-forget vs. complete control of MQTT message generation

Free, open-source MQTT performance tools follow the "fire-and-forget"
paradigm: you configure message generation in advance, then fire the
tool to perform the load testing.

This is fine for static scenarios, but when are real-world scenarios
static? Message characteristics change all the time: sensors connect and
disconnect, you get Denial-of-Service (DOS) attacks or mal-functioning
sensors (the "crying baby" scenario). How will you test that your
application load balancer (ALB) throttles misbehaving connections in

MIMIC MQTT Simulator lets you change any message characteristic
(frequency, topic, payload, QOS, etc) at any point in real-time, not just for
one sensor, but also for many thousands if not millions. This allows you to
create anomaly scenarios that simpler tools don't allow you to.

In this 4-minute Youtube video we show our open-source "MQTT Topic
Statistics" mqtt-stats  subscriber client connected to a IBM MessageSight
broker instance. MIMIC MQTT Simulator is used to generate different
message loads dynamically during the video, verified by mqtt-stats.

In the simulator we first start 10 simulated Sparkplug sensors. Each
sensor publishes to 3 topics (NBIRTH, DBIRTH and DDATA) in order to generate
telemetry. By default each is sending 1 DDATA message per second.

In the steady-state (when all sensors are registered) mqtt-stats shows the 30
topics and 10 active topics (see in video). We show the 10 NBIRTH, DBIRTH,
and DDATA topics as defined in the Sparkplug specification. At this point we
can clear out the topics with File -> New to only show the active DDATA
topics. All sensors are showing a rate of 1 message / second.

Now we can change message rates dynamically, we pick 2 sensors to send 5, then
10, then 20 messages / second. Then we pick 3 different sensors and change their
frequency to 50 / second. And yet a different one with 100 / second. Then we reset
all 10 back to 1 message / second.  What we did interactively you can script
programmatically with the MIMIC API in 6 languages.

The rest of the video show a total of 1000 sensors being monitored by the
mqtt-stats client.

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