Kafkaclients v0_11 : enhanced ConsumerConfig : property metric.reporters valued with hundreds of OpenTelemetryMetricsReporter className

[trudyq]

Describe the bug
For some internal projects still using an old Spring boot version (2.1.3) and old Kafka client version i found, after multiple iterations, enhanced Kafka ConsumerConfigs with the property "metric.reporters" valued with the same value io.opentelemetry.javaagent.shaded.instrumentation.kafka.internal.OpenTelemetryMetricsReporter hundreds of times.

Steps to reproduce
Create multiple consumer based on the same ConsumerConfig

What did you expect to see?

Just one OpenTelemetryMetricsReporter !

metric.reporters = [io.opentelemetry.javaagent.shaded.instrumentation.kafka.internal.OpenTelemetryMetricsReporter]

What did you see instead?

...
bootstrap.servers = [kafka1:9093, kafka2:9093, kafka3:9093]
...
metric.reporters = [io.opentelemetry.javaagent.shaded.instrumentation.kafka.internal.OpenTelemetryMetricsReporter,
 io.opentelemetry.javaagent.shaded.instrumentation.kafka.internal.OpenTelemetryMetricsReporter,
 io.opentelemetry.javaagent.shaded.instrumentation.kafka.internal.OpenTelemetryMetricsReporter,
 io.opentelemetry.javaagent.shaded.instrumentation.kafka.internal.OpenTelemetryMetricsReporter,
... hundred of times ...
 io.opentelemetry.javaagent.shaded.instrumentation.kafka.internal.OpenTelemetryMetricsReporter,
 io.opentelemetry.javaagent.shaded.instrumentation.kafka.internal.OpenTelemetryMetricsReporter,
 io.opentelemetry.javaagent.shaded.instrumentation.kafka.internal.OpenTelemetryMetricsReporter,
 io.opentelemetry.javaagent.shaded.instrumentation.kafka.internal.OpenTelemetryMetricsReporter
]
...

What version are you using?
OpenTelemetry agent 1.20.2
Sprint Boot 2.1.3
Spring-kafka 2.2.2-RELEASE

Additional context
In the code below, the check "Does OpenTelemetryMetricsReporter already exists in the property ?" is missing. So config.merge always add the same value.

https://github.com/open-telemetry/opentelemetry-java-instrumentation/blob/release/v1.24.x/instrumentation/kafka/kafka-clients/kafka-clients-0.11/javaagent/src/main/java/io/opentelemetry/javaagent/instrumentation/kafkaclients/v0_11/KafkaSingletons.java#L74-L77

[trudyq]

Thanks !