Mini Cluster of ESP32

There are three ESP32 modules serving as workers. They are connected with PC via USB ports in order to show their stdout on screen. The white PyCharm IDE window runs code of client and broker . When we start the client, which is a “Word Count“ program, we firstly send command via MQTT and reset workers. Workers flash LED when connect to MQTT broker. Wait 15 seconds for workers to initialize and settle down. Client pushs tasks into queue, workers are noticed and fetching tasks from remote queue. Workers flash LED when fetch a task successfully. Worker execute fetched task, return the result, and fetch the next task from remote queue. They go on and on until all tasks are done and the remote queue is empty. The architecture is symmetric, it means that each ESP32 module has a task queue in it, and can call other workers for help.