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MetricsService API

The MetricsService protocol provides two functions: get-metrics-registry and update-registry-settings.

get-metrics-registry

Takes an optional registry domain as a keyword. Returns the Dropwizard MetricRegistry for that domain, which can then be used to register new metrics. If no registry for this domain previously existed, creates the metric registry. If no domain is provided, returns the default registry.

Can be called at any time, regardless of if or when update-registry-settings has been called.

update-registry-settings

Takes a domain and a map of settings, and registers these settings for the domain. Currently, the only available setting is default-metrics-allowed, which takes a vector of strings.

This function can safely be called multiple times from different Trapperkeeper services. Since the only setting is currently default-metrics-allowed, each call to update-registry-settings will append the given default-metrics-allowed list to the existing list of allowed metrics for that domain. This means that different services can add metrics to the allowed list that are appropriate for that service, so that no one service needs to know the complete list of allowed metrics for the entire TK application

Any calls to this function must be called during the init phase of the service lifecycle, since these settings are used to initialize registries and reporters during the metrics service's start phase.

Example usage:

(trapperkeeper/defservice my-service
  [[:MetricsService get-metrics-registry update-registry-settings]]
  (init
   [this context]
   (update-registry-settings :foo {:default-metrics-allowed ["foo" "foo.bar"])
   ...)
  (start
   [this context]
   (let [registry (get-metrics-registry :foo)]
     (core/do-something-with-metrics registry))
   ...))

Registry settings

default-metrics-allowed

This setting allows for specifying a list of metric names (as strings) that will be exported to configured reporters (e.g. Graphite - note that this setting does not apply to JMX). See Metrics Filtering for more info.