Logstash is overwriting output elasticsearch

Is it possible to add a field in elasticsearch output only if the document in the index does not contain that field?

I'm trying to fetch data from a API (using the input http_poller) and storing the data in a elasticsearch index (using output elasticsearch). If the index does not contains a specific field i want to add it (with a default value). I need to check its existence because I have action 'update' and doc_as_upsert true.

Currently I'm using the "add_field" in the http_poller but at every schedule it overwrite the current value of the field stored in the index.


input {
  http_poller {
    urls => {
      test1 => "http://localhost:9000/test"
    request_timeout => 60
    schedule => { cron => "* * * * *"}
    codec => "json"
    metadata_target => "http_poller_metadata"
	add_field => { "status" => "active"}

output {
	elasticsearch {
		hosts => ["localhost:9200"]
		index => "test-2020.08.31"
		document_id => "%{[uid]}"
		action => 'update'
		doc_as_upsert => true

When the value of "status" change after a schedule (eg. from "active" to "stopped") at the next schedule it will overwrite the current value (from "stopped" to "active")