MQTT で受信したデータをファイルに書き出す

プログラム

subscribe_log.py

#! /usr/bin/python
#
#	subscribe_log.py
#
#						Dec/14/2022
#
# ------------------------------------------------------------------
import sys
import json
from time import sleep
import paho.mqtt.client as mqtt
import time

# ------------------------------------------------------------------
def log_write_proc(json_str):
#	print(json_str)
	unit_aa = json.loads(json_str)
#
	print(unit_aa)
#
	fp_out = open(file_log,mode='a', encoding='utf-8')
	fp_out.write(json_str + "\n")
	fp_out.close()
# ------------------------------------------------------------------
def on_connect(client, userdata, flags, respons_code):
#	print('status {0}'.format(respons_code))
	client.subscribe(topic)

# ------------------------------------------------------------------
def on_message(client, userdata, msg):
#	print(msg.topic + ' ' + str(msg.payload,'utf-8'))
	log_write_proc(str(msg.payload,'utf-8'))

# ------------------------------------------------------------------
sys.stderr.write("*** 開始 ***\n")

#host = '35.75.37.18'
# topic = 'esp32/test'
host = sys.argv[1]
topic = sys.argv[2]
port = 1883

file_log = "/tmp/" + topic + ".log"
sys.stderr.write(host + "\n")
sys.stderr.write(topic + "\n")
sys.stderr.write(file_log + "\n")
#

client = mqtt.Client(protocol=mqtt.MQTTv311)

client.on_connect = on_connect
client.on_message = on_message

client.connect(host, port=port, keepalive=60)

client.loop_forever()

sys.stderr.write("*** 終了 ***\n")
# ------------------------------------------------------------------

使い方

broker: example.com
topic: example/test
とすると、

./subscribe_log.py example.com example/test

実行前に、/tmp/example を作成して下さい。
次のファイルが作成されます。

/tmp/example/test.log

Systemd で動かす

プログラムを、
/usr/local/subscribe
に置いて下さい。

/etc/systemd/system/subscribe_temperature_log.service

[Unit]
Description = start up mqtt_client subscribe_temperature_log

[Service]
WorkingDirectory=/var/tmp/subscribe_log
ExecStart=/usr/local/subscribe/subscribe_log.py example.com example/test
Type=simple

[Install]
WantedBy=default.target

作業用の Directory を作成

mkdir /var/tmp/subscribe_log

起動

sudo systemctl start subscribe_temperature_log

起動したことを確認

sudo systemctl status subscribe_temperature_log