MQTT Playground

playground to evaluate common coding paradigms in different languages

Task

Write a program that connects to a local MQTT instance. Once connection is established, start a consumer thread, that listens on the "ping/#" topic. Continuously listen on the the topic.

Further, include a logging facade implementation. On program start, log a message

[main] Hello MQTT

Everytime a message is received on any of the ping topics, log a message

[consumer/ping/{topic}] Received {message}

Next, the main thread should spawn 10 producer threads. Every producer creates its own topic to publish on: ping/<uuid>. Every second, a producer sends a message ping:<nonce> starting with ping:0. The nonce is then incremented, and the Thread is put to sleep for 1 second. The thread should then loop back to the publish.

After all 11 threads are spawned, the main thread sleeps for 10 seconds, closes the connection, and stops the program.

Evaluation of practices

The following coding practices may be evaluated:

• use a library (MQTT), which is similar in implementation on most platforms
• use a logging facade, implement a simple logger, and configure the log-level
• use a common UUID implementation
• use the StringBuilder pattern
• spawn a thread
• handle continuous streams without disruption
• write into a log output
• spawn n threads, looping indefinitely
• put spawned threads to sleep
• asynchronously use a single connection (depends on the MQTT implementation)

Prerequisites

Use an MQTT Broker. An example would be mosquitto.

# start as a daemon
systemctl start mosquitto

# start in a shell
mosquitto

# continuously log all messages published to the topic "ping/#"
mosquitto_sub -t "ping/#"

# log all topics and messages
mosquitto_sub -v -t "#"

# publish a message on "ping/1"
mosquitto_pub -t "ping/1" -m "ping:0"