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MQTT interface example

KxSystems/mqtt

This example requires

The example below outlines a minimal use case which publishes data on multiple topics from kdb+ to a Mosquitto broker and subscribes to these topics from a separate kdb+ process. The steps are

Open a Mosquitto broker

Open a Mosquitto broker on the default localhost tcp://localhost:1883.

Start two kdb+ processes

From the examples folder, start two q processes.

Load the test producer

Load the test producer script on one of the processes to publish messages to topics topic1 and topic2.

q)\l producer.q
// Type `\t 100` to publish a message every 100ms 
// for up to 200 messages. To stop at any time type `q)\t 0`
q)\t 100
(`msgsent;1)
(`msgsent;2)
(`msgsent;3)
(`msgsent;4)
q)\t 0

Load the test receiver

On the other process load the test receiver script, which updates messages from topics topic1 and topic2

q)\l receiver.q
"Message received"
"Message received"
"Message received"
"Message received"

// Display messages being added to .mqtt.tab
q).mqtt.tab
topic  msg_sent                      msg_recv                      recieved_m..
-----------------------------------------------------------------------------..
topic1 2019.07.29D10:47:19.185993000 2019.07.29D10:47:19.186598000 topic1_0  ..
topic2 2019.07.29D10:47:19.186129000 2019.07.29D10:47:19.286879000 topic2_0  ..
topic1 2019.07.29D10:47:20.187006000 2019.07.29D10:47:20.187568000 topic1_1  ..
topic2 2019.07.29D10:47:20.187124000 2019.07.29D10:47:20.287820000 topic2_1  ..