I’m trying to create a graph of normalized Throughput data. I have Throughput data points and I want to plot a graph of (Throughput / TotalThroughput) * 100, for any given period. I can use the Metric Script Field to apply a calculation to ‘_value’ (e.g. (_value / 6000000) * 100, given my TotalThroughput for the period is 6000000rpm), but the TotalThroughout will obviously change, based on the graph window.
Ideally, I need to be able to pick up, say, a Single Stat value for TotalThroughput dynamically and apply it to the Script Field as a variable, but I can’t see a way to do that! Another thought I had was to create a Template Variable that holds the TotalThroughput value, but I can’t see how to use a Template variable in the Script Field and have it interpreted before submitting the query. I know certain internal variables like ‘$interval’ and ‘$__interval_ms’ can be used in the field and they get interpreted before the query is submitted!
So, can I achieve what I need with Grafana? Can I reference dynamic variables or other metric values in the Metric Script Field?
My data source is Elasticsearch v5.4.0 and I’m using Grafana v4.6.0.
How do I define and use a ‘custom’ variable. I tried creating a Template Variable like so…
…but if I use the value in a Script Calculation like so…
…it doesn’t work. The Query Inspector shows that the literal variable text (i.e. $TotalThroughput) is inserted in the query, rather than the value I assigned to the variable (i.e. 18174).
And added (_value / $source) to the script field. This will of course create a bad query, but I can still see in query inspector that the template variable been replaced in the script field.
Could it be related to that you’re using a constant variable? What version of Grafana are you using?
OK, I followed your lead and experimented using the link you provided. I created a Constant Variable and was able to get it to work! So I went back to my installation and reproduced exactly what I did while experimenting. It also worked! So then I recreated exactly what I did in my previous post, using the same variable name and value, and IT also now works!!
I don’t know why it’s working today and didn’t work all the previous days I tried. You can see in the screen shots I provided that it didn’t work before.
Anyway, thanks for the help. You kept me looking at the issue and I know I have options now. I hope it continues to work.
