Accidental strict dep on LatencyUtils

[codefromthecrypt]

It seems there are some guards to try to not use LatencyUtils unless pause detection is in use. However, there's still a compile dep.

[INFO] Caused by: java.lang.ClassNotFoundException: org.LatencyUtils.IntervalEstimator
[INFO] 	at java.net.URLClassLoader.findClass(URLClassLoader.java:471) ~[?:?]
[INFO] 	at java.lang.ClassLoader.loadClass(ClassLoader.java:588) ~[?:?]
[INFO] 	at org.springframework.boot.loader.LaunchedURLClassLoader.loadClass(LaunchedURLClassLoader.java:93) ~[zipkin-server-2.16.3-SNAPSHOT-slim.jar:?]
[INFO] 	at java.lang.ClassLoader.loadClass(ClassLoader.java:521) ~[?:?]
[INFO] 	at io.micrometer.prometheus.PrometheusMeterRegistry.newTimer(PrometheusMeterRegistry.java:176) ~[micrometer-registry-prometheus-1.2.1.jar!/:1.2.1]
[INFO] 	at io.micrometer.core.instrument.MeterRegistry.lambda$timer$2(MeterRegistry.java:271) ~[micrometer-core-1.2.1.jar!/:1.2.1]
[INFO] 	at io.micrometer.core.instrument.MeterRegistry.getOrCreateMeter(MeterRegistry.java:576) ~[micrometer-core-1.2.1.jar!/:1.2.1]
[INFO] 	at io.micrometer.core.instrument.MeterRegistry.registerMeterIfNecessary(MeterRegistry.java:529) ~[micrometer-core-1.2.1.jar!/:1.2.1]
[INFO] 	at io.micrometer.core.instrument.MeterRegistry.timer(MeterRegistry.java:269) ~[micrometer-core-1.2.1.jar!/:1.2.1]
[INFO] 	at io.micrometer.core.instrument.Timer$Builder.register(Timer.java:477) ~[micrometer-core-1.2.1.jar!/:1.2.1]
[INFO] 	at io.micrometer.core.instrument.MeterRegistry.timer(MeterRegistry.java:396) ~[micrometer-core-1.2.1.jar!/:1.2.1]
[INFO] 	at io.micrometer.core.instrument.internal.TimedExecutorService.<init>(TimedExecutorService.java:40) ~[micrometer-core-1.2.1.jar!/:1.2.1]
[INFO] 	at io.micrometer.core.instrument.binder.jvm.ExecutorServiceMetrics.monitor(ExecutorServiceMetrics.java:94) ~[micrometer-core-1.2.1.jar!/:1.2.1]
[INFO] 	at io.micrometer.core.instrument.binder.jvm.ExecutorServiceMetrics.monitor(ExecutorServiceMetrics.java:107) ~[micrometer-core-1.2.1.jar!/:1.2.1]

[codefromthecrypt]

here's an example of another project working around a similar accidental strict dep line/armeria#2107

[codefromthecrypt]

It looks like HdrHistogram is also effectively mandatory, It would be nice for these to be optional.

java.lang.NoClassDefFoundError: org/HdrHistogram/DoubleRecorder
	at io.micrometer.core.instrument.distribution.TimeWindowPercentileHistogram.<init>(TimeWindowPercentileHistogram.java:37) ~[micrometer-core-1.2.1.jar!/:1.2.1]
	at io.micrometer.core.instrument.AbstractTimer.<init>(AbstractTimer.java:85) ~[micrometer-core-1.2.1.jar!/:1.2.1]
	at io.micrometer.prometheus.PrometheusTimer.<init>(PrometheusTimer.java:40) ~[micrometer-registry-prometheus-1.2.1.jar!/:1.2.1]
	at io.micrometer.prometheus.PrometheusMeterRegistry.newTimer(PrometheusMeterRegistry.java:176) ~[micrometer-registry-prometheus-1.2.1.jar!/:1.2.1]

[adriangonz]

Is this task currently prioritized for the next release? Is there any time estimate of when it would be ready?

If I can get a "deep dive tour" around the relevant areas of the codebase I would be happy to jump on this one!

[sheepdreamofandroids]

This problem still exists. At least declare the dependencies until you find a good way to make them optional.
My bad. I see now that the LatencyUtils dependency is declared. For some reason gradle 7.4.2 didn't include it in the jar until I explicitly declared as well. HdrHistogram was included out of the box for me.

[shakuzen]

LatencyUtils is currently a declared runtime dependency in micrometer-core. If you are using the default configuration (NoPauseDetector) then you should be able to exclude the LatencyUtils dependency in your application. In other words, it should be optional although it is declared. I tried excluding it and ran into an issue at runtime. I think we can easily improve that, at least, without affecting backwards compatibility.

[shakuzen]

Resolved by #3262

[shakuzen]

If you are not configuring a pause detector, you can exclude the LatencyUtils dependency.
If you are not configuring client-side percentiles, you can exclude the HdrHistogram dependency.