micrometer: High CPU usage while using KafkaStreamsMetrics

Describe the bug We run spring-boot + kafka-streams with micrometer and KafkaStreamsMetrics. Metrics are exposed by using micrometer-registry-prometheus

After upgrading from micrometer 1.7.3 to 1.7.4 we notice high cpu-usage. If we disable KafkaStreamsMetrics the high cpu usage disappear. Also, downgrading to 1.7.3 makes the high cpu usage disappear.

The cpu usage increases while calling actuator/prometheus. Our monitoring system polls this endpoint frequently and the CPU is therefore always high.

Have provided a small sample-app that reproduces the issue: https://github.com/JorgenRingen/micrometer_1_7_4_high_cpu_usage

Environment Kubernetes and locally.

• Micrometer version: 1.7.4
• Micrometer registry: prometheus
• OS: macOS, Linux
• Java version: openjdk version “11.0.7”

To Reproduce How to reproduce the bug: https://github.com/JorgenRingen/micrometer_1_7_4_high_cpu_usage Java-branch has a very basic spring-boot, kafka-streams, micrometer setup.

Expected behavior While polling localhost:8080/acutator/prometheus the CPU usage is very high on 1.7.4. Expected behavior is that this should barely be noticeable.

Additional context Slack thread: https://micrometer-metrics.slack.com/archives/C662HUJC9/p1632729969102400