Add_field not getting the field

Thank you for the Reply badger!

i am a newbie to logstash and Ruby, for the code you mentioned, i got the following error:

Feb 14 20:28:21 oriontvpiasi024 logstash[8674]: [2020-02-14T20:28:21,153][ERROR][logstash.filters.ruby ][main] Ruby exception occurred: undefined method `is?' for #Hash:0x56f9c6ef

there isnt something like that?

mutate{
add_field => {"UPLINK" => "[service_data_container][Accounting-Output-Octets]"}
}

how can i get the nested information in the add_field ?

however i really need to learn ruby by the way...

thanks in advance!