sensors module fix

[ilyam8]

Summary

Fix: #4602

Component Name

python module sensors

Additional Information

bug trace:

2018-11-12 21:25:49: python.d ERROR: sensors: sensors: check() unhandled exception: Can't read
2018-11-12 21:25:49: python.d ERROR: sensors: sensors: Traceback (most recent call last):
File "./plugins.d/python.d.plugin", line 317, in check_job
check_ok = bool(job.check())
File "/opt/netdata/usr/libexec/netdata/python.d/sensors.chart.py", line 144, in check
self.create_definitions()
File "/opt/netdata/usr/libexec/netdata/python.d/sensors.chart.py", line 120, in create_definitions
vals = [sensors.get_value(chip, sf.number) for sf in sfi]
File "/opt/netdata/usr/libexec/netdata/python.d/python_modules/third_party/lm_sensors.py", line 181, in get_value
raise Exception(strerror(err))
Exception: Can't read

quick fix:
skip unreadable values

---

@hznovich please test the fix

Module is small but extremely hard to read.

[Ferroin]

Wait, so the lm_sensors module actually raises a bare Exception if it fails a read?

If so, that should be reported upstream as a bug (or we should update if it's fixed upstream), nothing should ever raise Exception directly.

[ilyam8]

actually raises a bare Exception if it fails a read?

it raises nothing except bare Exception actually

netdata uses this

[ilyam8]

lm_senors
readme, Missing Features (pull requests are welcome) section:

• Error handlers

@Ferroin 😄

[Ferroin]

I guess I'll be submitting a PR to that then to add a local Exception sub-class for it to throw...

Short term, this is fine, but we really should not be catching a bare exception and blindly ignoring it.

[Ferroin]

PR created upstream to add something saner for us to catch: paroj/sensors.py#2

Hopefully the author is still around, it's been 8 months since the last commit.

[ilyam8]

Author is very active on github, i am sure it will respond soon.

How about to mirror C code errors btw?

like

this is our get_value

error codes

Implementation:

ERR_WILDCARDS = 1
ERR_NO_ENTRY = 2

class SensorsError(Exception):
    pass

class ErrorWildcards(SensorsError):
    pass

class ErrorNoEntry(SensorsError):
    pass

...
def is_error(idx):
    return idx < 0


def error_factory(idx):
    idx = abs(idx)

    if idx == ERR_WILDCARDS:
        return ErrorWildcards
    elif idx == ERR_NO_ENTRY:
        return ErrorNoEntry


...
    err = _hdl.sensors_parse_chip_name(orig_name.encode("utf-8"), byref(ret))
    
    if is_error(err):
        raise  error_factory(err)(strerror(err))

?

[Ferroin]

I was just trying for something quick to make sure it was usable. I'll probably post an update to it to mirror C errors, but that will probably have to wait until tomorrow.

[ktsaou]

merge?

[ilyam8]

@Ferroin upstream is fixed, do you have time to update netdata's lm_sensors and sensors module?

[Ferroin]

Yes, I'll have a PR to do so later today.