Warning in logs => A gauge metric of an unknown type (org.jruby.specialized.RubyArrayOneObject) has been created for key: send_to

[willemdh]

Logstash 7.13.1 from RPM with systemd, Red Hat 8

After starting to use inter pipeline communication with the pipeline output, I started seeing the following warnings in our Logstash logs:

[2021-07-28T17:34:33,187][WARN ][org.logstash.instrument.metrics.gauge.LazyDelegatingGauge][net-sflow-01] A gauge metric of an unknown type (org.jruby.specialized.RubyArrayOneObject) has been created for key: send_to. This may result in invalid serialization.  It is recommended to log an issue to the responsible developer/development team.
[2021-07-28T17:34:33,189][WARN ][org.logstash.instrument.metrics.gauge.LazyDelegatingGauge][net-sflow-01] A gauge metric of an unknown type (org.jruby.specialized.RubyArrayOneObject) has been created for key: send_to. This may result in invalid serialization.  It is recommended to log an issue to the responsible developer/development team.

Speicific configuration triggering the above warning:

output {
    if [sflow_type] == "flow_sample" or [sflow_type] == "expanded_flow_sample" {
        pipeline { 
            send_to => ["net-sflow-sample-01"]
        }
    }
    else if [sflow_type] == "counter_sample" {
        pipeline { 
            send_to => ["net-sflow-counter-01"]
        }
    }
}

[yaauie]

For now, this warning should be internal-facing to the Logstash team, and is not something that users of Logstash need to worry about.

The results of this metric are polled from the node stats API, and we have observed no issues serializing arrays of strings there.

[shaunbugler]

Can confirm I am still seeing this with logstash 8.4.1 [2022-09-15T09:27:56,066][WARN ][org.logstash.instrument.metrics.gauge.LazyDelegatingGauge][beats_input_into_logstash] A gauge metric of an unknown type (org.jruby.specialized.RubyArrayOneObject) has been created for key: send_to. This may result in invalid serialization. It is recommended to log an issue to the responsible developer/development team.

[anubisg1]

and still existing in 8.5.2

[limdoglim]

7.17.8 too

[joel-jeremy]

Still existing in 8.7.0

[k001]

Still facing in logstash-7.16.3-1.x86_64

[ash-darin]

For now, this warning should be internal-facing to the Logstash team, and is not something that users of Logstash need to worry about.

The results of this metric are polled from the node stats API, and we have observed no issues serializing arrays of strings there.

If this is supposed to be "internal-facing" and "users of Logstash need [not] to worry about", is it possible to downgrade this to a DEBUG message, so users don't have to bother with it? It's quite tedious to actively ignore/filter all the messages I do not have to "worry" about and can "ignore".

[hsousa79]

and.. still facing in logstash 8.11.3

[sbmagar13]

and still facing in logstash 8.14.3