cache metrics are always reported

[himanshug]

various metrics reporting monitors are enabled by user via putting them in druid.monitoring.monitors property. However, org.apache.druid.client.cache.CacheMonitor is enabled (hardcoded) on brokers and historicals via MetricsModule.register(binder, CacheMonitor.class); in CliBroker and CliHistorical

We currently don't use caching in our cluster but all cache metrics are periodically reported via the emitter creating unnecessary noise in the logs (we use LoggingEmitter) . There is no way to disable these.

can we remove the hardcoding from CliBroker and CliHistorical , let user add org.apache.druid.client.cache.CacheMonitor to druid.monitoring.monitors if they need them like any other metrics monitor.

[giom-l]

Hi,
Also noticed that a few days ago when I tried to deactivate cache metrics (as we don't use cache neither for now).
Wondering if that could be even possible to NOT send metrics if useCache is set false ?

monitor	useCache	metric send ?
druid.monitoring.monitors=['org.apache.druid.client.cache.CacheMonitor']	druid.broker.cache.useCache=true	yes
druid.monitoring.monitors=['org.apache.druid.client.cache.CacheMonitor']	druid.broker.cache.useCache=false	no

Same thing for historical