count bound and enable stats

[tbradellis]

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Overview

newrelic-java-agent/newrelic-agent/src/main/java/com/newrelic/agent/tracers/metricname/MetricNameFormats.java

Lines 21 to 23 in 4b53e4f

private static final Cache<MNFKey, MetricNameFormat> cmsToMnf = Caffeine.newBuilder()
.executor(Runnable::run)
.build();
If a customer were to create enough segments with extremely dynamic names, this cache could grow to an unreasonable size and appear to be a memory leak.

Related Github Issue

#1825

Considerations

This could optionally be bound by some weighting. However, seems like a simple count bound would probably work for this cache. Somewhat arbitrarily around 10K? Or do you have metrics showing distribution of common counts? This is essentially just every tracer right?

Would you want this configurable?

Any interest in recording stats for this cache? If not, will just remove recordStats()
and/or logging spikes?
if (cmsToMnf.stats().evictionCount() > threshold) {
logger.warn("High MetricNameFormat cache eviction rate detected!");
}

Testing

Dependent on complete changes

Checks

• [ √] Your contributions are backwards compatible with relevant frameworks and APIs.
• [ √] Your code does not contain any breaking changes. Otherwise please describe.
• [√ ] Your code does not introduce any new dependencies. Otherwise please describe.

[jtduffy]

@tbradellis You've been around these parts before huh? :-)

We're going to keep this open and see if we can generate some stats on what the size max size of the cache should be. Thanks!