@Override
    public void metricChange(KafkaMetric metric) {
        /*
         metrics collector may not have been initialized (e.g. invalid context labels)
         in which case metrics collection is disabled
        */
        if (kafkaMetricsCollector != null) {
            kafkaMetricsCollector.metricChange(metric);
        }
    }
Method is invoked whenever a metric is added/registered
clients/src/main/java/org/apache/kafka/common/telemetry/internals/ClientTelemetryReporter.java