Add class name and class regex filters

[AlexandreYang]

What this PR does

Add class name and class regex filters

Motivation

Allow creating rules based on class name filters.

For example Kafka / Confluent Platform uses yammer metrics that provide different MBean classes like Gauge, Histogram, Timer, Meter. Since each class have different attributes and require specific rules, a filter by class can be helpful in targeting all metrics from a specific MBean class.

The classes are like follow:

- com.yammer.metrics.reporting.JmxReporter$Gauge
- com.yammer.metrics.reporting.JmxReporter$Histogram
- com.yammer.metrics.reporting.JmxReporter$Timer
- com.yammer.metrics.reporting.JmxReporter$Meter

That will allow creating rules tailored to each class:

jmx_metrics:
  - include:
      domain_regex: kafka\..*
      class_regex: .*$Gauge
      attribute:
        Value:
          alias: $domain.$type.$name
          metric_type: gauge
  - include:
      domain_regex: kafka\..*
      class_regex: .*$Histogram
      attribute:
        Count:
          alias: $domain.$type.$name.count
          metric_type: count
        Mean:
          alias: $domain.$type.$name.avg
          metric_type: gauge
        99thPercentile:
          alias: $domain.$type.$name.99percentile
          metric_type: gauge

[truthbk]

Looks pretty good to me, fits in nicely with previous pattern matching code.

I think we can get rid of the Mbean empty class file. Let me know if what I mean is not clear.

[truthbk]

Not sure we need this in a new file, I think it'll be better if you use an inner class in TestApp.java.

[AlexandreYang]

@truthbk thx for the feedback.

Yes, the initial reason to use a new file was to have a simpler name to match. But it's it's probably fine to use an inner class too. Changed in my last commit.

Using a separate class:

class: org.datadog.jmxfetch.SimpleTestJavaApp2

Using a inner class:

class: org.datadog.jmxfetch.TestApp$1SimpleTestJavaAnotherApp

[truthbk]

note to self: I was going to say these new log lines perhaps didn't add much value, but since we're calling methods on connection we can probably trigger an IOException with these, so it's probably justified.

[truthbk]

🍰

[truthbk]

Looks good! 🚀