Error while running logstash: org.logstash.instrument.metrics.gauge.LazyDelegatingGauge

[elen]

Hello,

Trying to send data Logstash -> Elasticsearch ( both are running in docker, configs are tested and are ok) and I'm experiencing issue that actual data is not sent (this is the only warning I get while running logstash conf file):

[2020-05-07T18:09:30,166][WARN ][org.logstash.instrument.metrics.gauge.LazyDelegatingGauge][main] A gauge metric of an unknown type (org.jruby.specialized.RubyArrayOneObject) has been create for key: cluster_uuids. This may result in invalid serialization. It is recommended to log an issue to the responsible developer/development team.
** -----------------------------------------------------------------------**

#logstash config file: 

input { 
file { 
       path => "/root/metricbeat.log" 
       start_position => "beginning" sincedb_path => "/dev/null" 
} 
}

filter { 
} 

output { 
       elasticsearch { hosts => ["http://localhost:9200"] 
       index => "test-logstash" 
} 
stdout {} 
}

---

I am using 7.5.1 version for elasticsearch and logstash

Thanks in advance.