How to delete a single value from graphite's whisper data?

Question

I need to delete selected values from a graphite whisper data set. It is possible to overwrite a single value just by sending a new value, or to delete the whole set by deleting the .wsp file, but what I need to do is delete just one (or several) selected values, ie reset them to the same state as if they had not been written (undefined, graphite returns nulls). Overwriting doesn't do that.

How to do it? (Programmatically is ok)

See also:

• How to cleanup the graphite whisper's data?
• Removing spikes from Graphite due to erroneous data

Answer 1

Graphite (whisper) usually ships with whisper-update utility You can use it to modify the content of a wsp file:

whisper-update.py [options] path timestamp:value [timestamp:value]*

If the timestamp you want to modify is recent (as defined by carbon), you may want to wait or shutdown your carbon-cache daemons.