System Monitor disk usage reports identical values for all devices

[attila123456]

The problem

After upgrading to 2021.5.0 I noticed that all my disk usage widgets on the dashboard were showing identical values.
The code uses psutil.disk_usage(path) to check disk space, and when I ran the same command inside the home assistant docker container, in a python shell, it came back with correct values.

So after some digging in the code, I came across #48699 which seems to have introduced caching, which could cause an issue like this. Could it be using a single cached value for all disk usage/device entries?

What is version of Home Assistant Core has the issue?

2021.5.0

What was the last working version of Home Assistant Core?

2021.4.6

What type of installation are you running?

Home Assistant Container

Integration causing the issue

systemmonitor

Link to integration documentation on our website

https://www.home-assistant.io/integrations/systemmonitor/

Example YAML snippet

- platform: systemmonitor
    resources:
      - type: disk_use_percent
        arg: /
      - type: disk_free
        arg: /
      - type: disk_use_percent
        arg: /mnt/storage
      - type: disk_free
        arg: /mnt/storage
      - type: memory_free
      - type: memory_use
      - type: memory_use_percent
      - type: last_boot
      - type: load_1m
      - type: load_5m
      - type: load_15m

Anything in the logs that might be useful for us?

No response

Additional information

No response

[ColinRobbins]

I’ve seen this too.
The problem seems to relate to the recent update to add a dictionary to update all values in one update operation.

To me, the sensor_registry seems to be based on a type (disk_usage) having single values, not multiple.

During set up, line 228 in systemmonitor/sensor.py sets up sensor_registry, where _type is what the sensor should monitor and argument is the path name.

sensor_registry[type_] = SensorData(argument, None, None, None, None)

If this is called for a 2nd or 3rd time, the previous value of argument is lost.

Line 229 creates a new SystemMonitorSensor per config line

  entities.append(SystemMonitorSensor(sensor_registry, type_, argument))

and uses the registry as the data store.

Thus when the 2nd or 3rd sensor of the same type is added they all share the same sensor_registry data, so all see the same value. Thus any data presented by the sensor is duplicated.

[artlov]

I can confirm. I found same issue after core upgrade.

- platform: systemmonitor
 resources:
   - type: disk_free
     arg: /
   - type: disk_free
     arg: /share
   - type: disk_free
     arg: /media


config $ df -hT
Filesystem           Type            Size      Used Available Use% Mounted on
overlay              overlay       195.9G      7.9G    178.0G   4% /
/dev/nvme0n1p2       ext4           27.4G      4.6G     21.3G  18% /share
/dev/nvme0n1p5       ext4          697.4G    593.6G     68.3G  90% /media

[ColinRobbins]

I have fixed it in my local environment, had have just created a pull request #50362

[ColinRobbins]

Should be fixed in 2021.5.2