thresholdmon AttributeError crash

[Morten Brekkevold]

The fix for bug 1316608, introduced in NAV 4.3.3, enables the nav.metrics.lookup() function to return objects that are not Django models.

The threshold monitor makes the assumption that all looked-up objects from this API are Django model objects, causing the threshold monitor to crash when generating some threshold events. For example, when a "CPU" threshold is exceeded, the object returned by the lookup API will be a string or unicode object, causing an attribute access to fail.

The traceback from cron mail looks like this:

Traceback (most recent call last):
  File "/usr/lib/nav/thresholdmon", line 16, in <module>
    main()
  File "/usr/lib/python2.7/dist-packages/nav/thresholdmon.py", line 47, in main
    scan()
  File "/usr/lib/python2.7/dist-packages/nav/thresholdmon.py", line 86, in scan
    evaluate_rule(rule, alerts)
  File "/usr/lib/python2.7/dist-packages/nav/thresholdmon.py", line 135, in evaluate_rule
    end_event(rule, metric, value)
  File "/usr/lib/python2.7/dist-packages/nav/thresholdmon.py", line 167, in end_event
    event = make_event(False, rule, metric, value)
  File "/usr/lib/python2.7/dist-packages/django/db/transaction.py", line 224, in inner
    return func(*args, **kwargs)
  File "/usr/lib/python2.7/dist-packages/nav/thresholdmon.py", line 183, in make_event
    _add_subject_details(event, metric, varmap)
  File "/usr/lib/python2.7/dist-packages/nav/thresholdmon.py", line 195, in _add_subject_details
    table=getattr(obj, '_meta').db_table,
AttributeError: 'unicode' object has no attribute '_meta'

[Morten Brekkevold (mbrekkevold)]

fix here: https://nav.uninett.no/hg/stable/rev/bf4623ed4efc