Custom Metrics Reporters

[Phil Monroe]

Hey,

How would I create and register a new custom metrics reporter? I want to extend the current graphite reporter and have it inject the hostname into the prefix when sending metrics. Here is what I have:

MygraphiteReporterFactory.scala:

package io.dropwizard.metrics

import com.fasterxml.jackson.annotation.JsonTypeName

import io.dropwizard.metrics.graphite.GraphiteReporterFactory

@JsonTypeName("mygraphite")

class MygraphiteReporterFactory extends GraphiteReporterFactory {

  override def getPrefix() = s"${super.getPrefix}.HOST"

}

config.yml:

metrics:

  reporters:

    - type: mygraphite

      host: graphite.example.com

      prefix: syman2

error on startup:

config.yml has an error:

  * Failed to parse configuration at: metrics.reporters; Could not resolve type id 'mygraphite' into a subtype of [simple type, class io.dropwizard.metrics.ReporterFactory]

 at [Source: N/A; line: -1, column: -1] (through reference chain: com.example.Config["metrics"]->io.dropwizard.metrics.MetricsFactory["reporters"])

What am I missing?

Thanks!

Phil

[Phil Monroe]

Ah ha! Figured it out.

Dropwizard uses text files inside of `src/main/resources/META-INF/services/*` to figure out what classes are discoverable. 

So i just needed to add this to `src/main/resources/META-INF/services/io.dropwizard.metrics.ReporterFactory`

io.dropwizard.metrics.MygraphiteReporterFactory

FYI: This is all done through the `DiscoverableSubtypeResolver` class:

https://github.com/dropwizard/dropwizard/blob/master/dropwizard-jackson/src/main/java/io/dropwizard/jackson/DiscoverableSubtypeResolver.java

Which gets attached to object mappers here:

https://github.com/dropwizard/dropwizard/blob/master/dropwizard-jackson/src/main/java/io/dropwizard/jackson/Jackson.java#L27

[Nick Telford]

Hi Phil,

This is exactly right. We use Java's SPI (Service Provider Interface) for all the pluggable Connectors (jetty), Reporters (metrics) and Appenders (logback).

As for your feature: it might be a neat idea for the GraphiteReporter to automatically replace "patterns" in the prefix; "%host" for example. What do you think?