KafkaStreamsBinderMetrics throws ClassCastException

on the start up of application, when metrics is binded to MeterRegistry by org.springframework.cloud.stream.binder.kafka.streamsKafkaStreamsBinderMetrics. I am getting following error: ` java.lang.ClassCastException: class java.lang.Long cannot be cast to class java.lang.Double (java.lang.Long and java.lang.Double are in module java.base of loader ‘bootstrap’) at org.springframework.cloud.stream.binder.kafka.streams.KafkaStreamsBinderMetrics$1.lambda$toDoubleFunction$0(KafkaStreamsBinderMetrics.java:92) ~[spring-cloud-stream-binder-kafka-streams-3.0.0.RELEASE.jar!/:3.0.0.RELEASE] at io.micrometer.core.instrument.internal.DefaultGauge.value(DefaultGauge.java:54) ~[micrometer-core-1.3.1.jar!/:1.3.1] at io.micrometer.prometheus.PrometheusMeterRegistry.lambda$newGauge$3(PrometheusMeterRegistry.java:245) ~[micrometer-registry-prometheus-1.3.1.jar!/:1.3.1] at io.micrometer.prometheus.MicrometerCollector.collect(MicrometerCollector.java:69) at io.prometheus.client.CollectorRegistry$MetricFamilySamplesEnumeration.findNextElement(CollectorRegistry.java:190) ~[simpleclient-0.7.0.jar!/:na] at io.prometheus.client.CollectorRegistry$MetricFamilySamplesEnumeration.nextElement(CollectorRegistry.java:223) at io.prometheus.client.CollectorRegistry$MetricFamilySamplesEnumeration.nextElement(CollectorRegistry.java:144) at io.prometheus.client.exporter.common.TextFormat.write004(TextFormat.java:22) ~[simpleclient_common-0.7.0.jar!/:na] at org.springframework.boot.actuate.metrics.export.prometheus.PrometheusScrapeEndpoint.scrape(PrometheusScrapeEndpoint.java:50) ~[spring-boot-actuator-2.2.1.RELEASE.jar!/:2.2.1.RELEASE] at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(NativeMethodAccessorImpl.java) ~[na:na] at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:566) at org.springframework.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:279) ~[spring-core-5.2.1.RELEASE.jar!/:5.2.1.RELEASE] at org.springframework.boot.actuate.endpoint.invoke.reflect.ReflectiveOperationInvoker.invoke(ReflectiveOperationInvoker.j.

`

[simsibimsiwimsi]

In https://github.com/spring-cloud/spring-cloud-stream-binder-kafka/blob/master/spring-cloud-stream-binder-kafka-streams/src/main/java/org/springframework/cloud/stream/binder/kafka/streams/KafkaStreamsBinderMetrics.java there is a cast to Double which causes the exception:

if (metric.metricValue() instanceof Number) {
    return (Double) metric.metricValue();
}

Programmatically it is probably not a good idea to check for Number and cast to Double instead as mentioned in https://stackoverflow.com/questions/32757565/java-lang-long-cannot-be-cast-to-java-lang-double. Instead I would suggest:

if (metric.metricValue() instanceof Number) {
    return ((Number) metric.metricValue()).doubleValue();
}

[Schwurbel]

The error occurs with the following dependencies:

org.springframework.boot:spring-boot-starter-webflux:2.2.2.RELEASE org.springframework.kafka:spring-kafka:2.3.4.RELEASE org.springframework.cloud:spring-cloud-stream:3.0.1.RELEASE org.springframework.cloud:spring-cloud-stream-binder-kafka:3.0.1.RELEASE