Append values to array field

[M.alsioufi]

After I read this topic:

Logstash Elasticsearch ouput: Append array while upserting

Results in the following error: "reason"=>"compile error", "caused_by"=>{"type"=>"illegal_argument_exception", "reason"=>"invalid sequence of tokens near ['%'].", "caused_by"=>{"type"=>"no_viable_alt_exception" Are you 100% sure all events have a [shodan][protocols] field? You'll have to double-quote the variable expansion, i.e. do this: script => 'ctx._source.shodan.protocols += "%{[shodan][protocols]}"' Which version of Logstash are you using? script => "%{[ctx][_source][shodan][protoc…

I modified the output config to become:
` output {
elasticsearch {
"hosts" => "http://myEShost:portnumber"
index => "my_index"
document_id => "%{a}"
action => "update"
script => 'if(ctx._source.b != null) ctx._source.b.add("%{b}");'

        }
        stdout {
            codec => json_lines
        }
    }`

but this is not doing the job it gives "version conflict, current version [77] is different than the one provided [76]"