Autostarting a python script at boot not working in /etc/rc.local and systemd

Question

I am working on a data acquisition project where I am sending a bunch of sensor data to the cloud. Here is a small snippet from my code:

#!/usr/bin/python3
# coding: utf-8

import ctypes
from systemd import journal
.
.
.#Rest of the code
.
journal.send(
        channel = 'sensor',
        priority = journal.Priority.INFO,
        messageid = "%d" % (seq_num),
        timestamp = "%s" % (CurrentTimestamp),
        tdiff = "%s" % (dt),     
        acc_x="%f" % (cax),
        acc_y="%f" % (cay),
        acc_z="%f" % (caz),
        gyr_x="%f" % (cgx),
        gyr_y="%f" % (cgy),
        gyr_z="%f" % (cgz),
        horn = "%d" % (GPIO.input(hornpin)),
        brake = "%d" % (GPIO.input(brakepin)),
        rpm = "%d" % (GPIO.input(rpmpin)),
        lux = "%f" % (lux),
        temperature_batterypack = "%d" % (temperature_batterypack),
        temperature_ambientair = "%d" % (temperature_ambientair),
        temperature_scooterbody = "%d" % (temperature_scooterbody),
        )

I have designed my own board using the public schematics of Raspberry Pi Compute module 3. The OS that I am using is the latest version of Raspbian Stretch Lite (June 2018 release). I am trying to autostart the code at boot by adding the following line in /etc/rc.local before exit 0:

sudo python3 /home/pi/test_scripts/cloud_test.py &

and I get the following error:

AttributeError: module 'systemd.journal' has no attribute 'Priority'

I even tried autostarting using systemd (so I created a service file) and when I check the status of the service file, it gives me the same exact error. Whereas, if I don't do auto start and manually run the code on the command prompt as:

$ python3 cloud_test.py

the code runs correctly and sends data to the cloud and I can see all the data on a website. This means all modules and python packages are correctly installed and I do not get any error. I also made by python script executable by using sudo chmod +x cloud_test.py and have also included #!/usr/bin/python3 at the top of my code. Then why do I see the error AttributeError: module 'systemd.journal' has no attribute 'Priority' only on autostart but not on manual start?

Answer 1

I have copy and pasted your test code and runs it from the command line:

rpi:~ $ ./cloud_test.py
Traceback (most recent call last):
  File "./cloud_test.py", line 12, in <module>
    priority = journal.Priority.INFO,
AttributeError: module 'systemd.journal' has no attribute 'Priority'
rpi:~ $

It seems there is no problem with starting the script in rc.local or with a systemd unit file. Instead there may be a problem with your test scripts. Do you really use the same script for bootup and for testing on the command line? Have a look at systemd.journal module what's with the attribute 'Priority'.

Answer 2

This issue was solved by reinstalling systemd module as sudo pip3 install systemd

Intially I did not include sudo while installing systemd.

It can also be solved by including User=pi in the service file.

[Unit]
Description = MESSI v2.0 sensor code
After=multi-user.target

[Service]
Type=idle
ExecStart=/usr/bin/python3 -u cloud_test.py
WorkingDirectory=/home/pi/test_scripts
Restart=always
User=pi

[Install]
WantedBy=multi-user.target

You can view the discussion here too: https://www.raspberrypi.org/forums/viewtopic.php?f=32&t=220304&p=1352497#p1352497