Logstash won't start pipeline after moving to 7.6.13 from 6.5.x

[fribse (Kenneth Fribert)]

Hi All, I've gotten a problem with my old logstash pipeline.

My config looks like this (everything is commented out during debugging):

[root@ALPHA00035 pipeline]# cat  logstash.conf
input {
        beats {
                port => 5000
                ecs_compatibility => disabled
        }
        syslog {
        }
}

#############################################
#  Interpret Portrait ERRORS    log         #
#############################################

#filter {
#       if "portraiterrors" in [fields][logtype] {
#       kv {
#                       source => "message"
#                       value_split => ":"
#                       field_split => "\n"
#                       include_keys => [ "Time", "Username", "Instance name", "Instancename", "Exception", "Exception type", "ErrorCode", "Module", "Procedure", "Version", "Memory usage" ]
#       }
#       if ![Instance name] {
#          mutate {
#            rename => { "Instancename" => "Instance name" }
#          }
#        }
#        date {
#                match => [ "Time", "MM/dd/yyyy HH:mm:ss aa", "M/d/yyyy HH:mm:ss aa", "M/d/yyyy H:m:ss aa", "dd-MM-yyyy HH:mm:ss", "d-M-yyyy HH:mm:ss", "MM/dd/yyyy", "M/d/yyyy", "dd-MM-yyyy", "d-M-yyyy" ]
#                timezone => "Europe/Copenhagen"
#        }
#  }
#}

#############################################


#############################################
#   Output to Elastic Search                #
#   Index name is defined by logtype        #
#############################################

output {
  elasticsearch {
    hosts => "https://elasticsearch:9200"
      index => "%{[[fields][logtype]}-%{[@metadata][version]}-%{+YYYY.MM}"
      document_type => "%{[@metadata][type]}"
      cacert => "/usr/share/logstash/config/certs/ca/ca.crt"
      user => logstash_internal
      password => <PW>
  }
}

But when I start logstash

logstash         | [2022-02-23T12:44:47,086][ERROR][logstash.javapipeline    ][main] Pipeline worker error, the pipeline will be stopped {:pipeline_id=>"main", :error=>"Invalid FieldReference: `[[fields][logtype]`"

So what am I doing wrong now?

[Badger]

@fribse

index => "%{[[fields][logtype]}...

Remove one of the two [ at the start of that reference.

[fribse (Kenneth Fribert)]

Ok, that's interesting, that error must've been there for ages, and I never noticed it and it worked with the old version
Thankyou very much @Badger