Comment 3 for bug 1475329

This happens when some of the measure awaiting processing by metricd have the same timestamp. That timestamp is the axis/index and pandas is not willing to have duplicates there.

That suggests some options, the last of which seems to be the least likely to cause havoc:

* raise granularity of timestamps
* ignore the entire current lump being processed when there is a ValueError that indicate
* drop measures of the same metric that have duplicate timestamps (presumably by using drop_duplicates: http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.drop_duplicates.html )