How can I change a tag name with a tick script (Kapacitor)?

Question

Let's say I have a measurement in my Influx db called 'cpu':

name: cpu
time                  host   app             org          usage_idle                                                     ----                  -----  ------------    ------------  ----------       
1505758901462105873  serverA  applicationA    org1           23
1505758901462106873  serverB  applicationA    org2           42

I wrote tick script to query data from this measurement:

var data = batch
        |query('''select 100-min(usage_idle) as used_percent from "application"."autogen"."cpu"''')
            .period(1m)
            .every(10s)
            .groupBy(time(1s), 'app', 'org', 'host')
            .align()

// Here I want to write Lambda? to change tag names

    data|influxDBOut()
            .database('someDataBase')
            .measurement('someMeasurement')
            .precision('s')

I want the result of this query contains instead of 'app' - 'app_name' , and instead of 'org' - 'app_group'. What should I include in tick script in order to change tag names? Note! As a workaround I can insert into result new columns with name 'app_name' and 'app_group', but I don't want to add more columns in there and have duplicate data.

Looking for some advice. Thank you

Answer 1

Here is the solution! The idea is to add a new tag and delete the old one (instead of renaming it). The above tick script then looks as the following:

var data = batch
        |query('''select 100-min(usage_idle) as used_percent from "application"."autogen"."cpu"''')
            .period(1m)
            .every(10s)
            .groupBy(time(1s), 'app', 'org', 'host')
            .align()


    |eval(lambda: "app")
            .as('app_name')
            .keep('used_percent')
            .tags('app_name')
    |delete()
            .tag('app') 

    |eval(lambda: "org")
            .as('app_group')
            .keep('used_percent')
            .tags('app_group')
    |delete()
            .tag('org') 

data|influxDBOut()
        .database('someDataBase')
        .measurement('someMeasurement')
        .precision('s')