Ceilometer Agent Notification: process_notification jsonpath error in the logs in

[Ashwin Agate]

In Ceilometer Agent Notification Logs see this exception (stable/rocky)

(ceilometer.pipeline.sample): 2019-04-10 22:52:54,463 ERROR sample process_notifications Fail to process notification
Traceback (most recent call last):
 File "/usr/lib//lib/python2.7/site-packages/ceilometer/pipeline/sample.py", line 46, in process_notifications
 p(list(self.build_sample(message)))
 File "/usr/lib//lib/python2.7/site-packages/ceilometer/meter/notifications.py", line 230, in build_sample
 for s in d.to_samples(notification):
 File "/usr/lib//lib/python2.7/site-packages/ceilometer/meter/notifications.py", line 124, in to_samples
 value = parser.parse(message)
 File "/usr/lib//lib/python2.7/site-packages/ceilometer/declarative.py", line 116, in parse
 values = self.getter(obj)
 File "/usr/lib//lib/python2.7/site-packages/jsonpath_rw/jsonpath.py", line 226, in find
 for subdata in self.left.find(datum)
 File "/usr/lib//lib/python2.7/site-packages/jsonpath_rw/jsonpath.py", line 228, in find
 for submatch in self.right.find(subdata)]
 File "/usr/lib//lib/python2.7/site-packages/jsonpath_rw/jsonpath.py", line 444, in find
 return [DatumInContext(datum.value[self.index], path=self, context=datum)]
KeyError: 0

It appears due to a mismatch in the notification payload and jsonpath expression specified to pull the data from raw notificaion that is specified in ceilometer/ceilometer/data/meters.d/meters.yaml for some notifications.

[jianyu li (easyljy)]

I encountered the same issue. In some conditions, the type of datum.value is dict instead of list.
I have below temporary fix in my environment, but not sure if it will break something.

444c444,447
< return [DatumInContext(datum.value[self.index], path=self, context=datum)]
---
> if type(datum.value) == list:
> return [DatumInContext(datum.value[self.index], path=self, context=datum)]
> else:
> return [DatumInContext(datum.value, path=self, context=datum)]