feat: support metrics sent via logger

lib/nexus_semantic_logger.rb

@@ -4,6 +4,7 @@ require 'nexus_semantic_logger/application'
 require 'nexus_semantic_logger/datadog_formatter'
 require 'nexus_semantic_logger/datadog_singleton'
 require 'nexus_semantic_logger/datadog_tracer'
+require 'nexus_semantic_logger/logger_metrics_subscriber'
 
 module NexusSemanticLogger
   # Get application wide object for sending metrics.

lib/nexus_semantic_logger/application.rb

@@ -39,6 +39,8 @@ module NexusSemanticLogger
 
       NexusSemanticLogger::DatadogTracer.new(service)
 
+      SemanticLogger.on_log(NexusSemanticLogger::LoggerMetricsSubscriber.new)
+
       logger.info('SemanticLogger initialised.', level: config.log_level)
 
       config.after_initialize do

lib/nexus_semantic_logger/logger_metrics_subscriber.rb

+# frozen_string_literal: true
+require 'semantic_logger'
+
+module NexusSemanticLogger
+  # Sends SemanticLogger metrics to statsd.
+  # This is a candidate to move into the nexus_semantic_logger gem if it becomes widely useful.
+  # See https://logger.rocketjob.io/metrics.html
+  # Based on https://github.com/reidmorrison/semantic_logger/blob/master/lib/semantic_logger/metric/statsd.rb
+  class LoggerMetricsSubscriber < SemanticLogger::Subscriber
+
+    def call(log)
+      log(log) if should_log?(log)
+    end
+
+    def log(log)
+      metric = log.metric
+      tags = log.payload.nil? ? nil : []
+      log.payload.each_pair { |key, value| tags << "#{key}:#{value}" } unless log.payload.nil?
+      if (duration = log.duration)
+        NexusSemanticLogger.metrics.timing(metric, duration, tags: tags)
+      else
+        amount = (log.metric_amount || 1).round
+        if amount.negative?
+          NexusSemanticLogger.metrics.decrement(metric, tags: tags)
+        else
+          NexusSemanticLogger.metrics.increment(metric, tags: tags)
+        end
+      end
+    end
+
+    # Only forward log entries that contain metrics.
+    def should_log?(log)
+      # Does not support metrics with dimensions.
+      log.metric && !log.dimensions && meets_log_level?(log) && !filtered?(log)
+    end
+  end
+end