feat: only print metrics warning once per thread

lib/pact/utils/metrics.rb

@@ -9,13 +9,17 @@ module Utils
     class Metrics
 
       def self.report_metric(event, category, action, value = 1)
+        do_once_per_thread(:pact_metrics_message_shown) do
+          if track_events?
+            Pact.configuration.output_stream.puts "pact WARN: Please note: we are tracking events anonymously to gather important usage statistics like Pact-Ruby version
+              and operating system. To disable tracking, set the 'PACT_DO_NOT_TRACK' environment
+              variable to 'true'."
+          end
+        end
+
         in_thread do
           begin
             if track_events?
-              Pact.configuration.output_stream.puts "WARN: Please note: we are tracking events anonymously to gather important usage statistics like Pact-Ruby version
-                and operating system. To disable tracking, set the 'PACT_DO_NOT_TRACK' environment
-                variable to 'true'."
-
               uri = URI('https://www.google-analytics.com/collect')
               req = Net::HTTP::Post.new(uri)
               req.set_form_data(create_tracking_event(event, category, action, value))
@@ -31,6 +35,7 @@ def self.report_metric(event, category, action, value = 1)
       end
 
       private
+
       def self.handle_error e
         if ENV['PACT_METRICS_DEBUG'] == 'true'
           Pact.configuration.output_stream.puts("DEBUG: #{e.inspect}\n" + e.backtrace.join("\n"))
@@ -43,6 +48,16 @@ def self.in_thread
         end
       end
 
+      # not super safe to use the thread, but it's good enough for this usecase
+      def self.do_once_per_thread(key)
+        result = nil
+        if !Thread.current[key]
+          result = yield
+        end
+        Thread.current[key] = true
+        result
+      end
+
       def self.create_tracking_event(event, category, action, value)
         {
           "v" => 1,