Graphite Tip - Converting Zeroes into Nulls

2013-04-01 17:43:26 by jdixon

I was looking at some internal data for @jnunemaker and @jfryman today when I stumbled across the Data Filters group of functions inside the Graphite composer. These functions are handy for those times when you want to exclude a subset of a particular series of data, for whatever reason. In our case, we were looking at some metrics where we had spikes of data that were interesting, and a lot of uninteresting data reported as zeroes.

By applying the removeBelowValue() function (found under Filters > Data Filters in the functions list) to our series, with a value of 1, we were able to convert all of those zeroes into nulls. From there, we could use lineMode=connected or keepLastValue() as our needs dictate.

Using removeBelowValue() with lineMode=connected:

And using removeBelowValue() with keepLastValue():

Note that there was a bug affecting the removeBelowValue() function in webapp/content/js/composer_widgets.js that has been fixed in master and 0.9.x branches of Graphite. You may want to manually apply the fix to your existing installations.

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