Add trace_ratio_sampled?

Now the trace ratio sampling logic lives in one method

Author: kaylareopelle

lib/new_relic/agent/transaction.rb

@@ -303,16 +303,19 @@ def sampled?
             false
           when 'trace_id_ratio_based'
             ratio = NewRelic::Agent.config[:'distributed_tracing.sampler.root.trace_id_ratio_based.ratio']
-            upper_bound = (ratio * (2**64 - 1)).ceil
-
-            ratio == 1.0 || trace_id[8, 8].unpack1('Q>') < upper_bound
+            trace_ratio_sampled?(ratio)
           when 'adaptive'
             NewRelic::Agent.instance.adaptive_sampler.sampled?
           end
         end
         @sampled
       end
 
+      def trace_ratio_sampled?(ratio)
+        upper_bound = (ratio * (2**64 - 1)).ceil
+        ratio == 1.0 || trace_id[8, 8].unpack1('Q>') < upper_bound
+      end
+
       def trace_id
         @trace_id ||= NewRelic::Agent::GuidGenerator.generate_guid(32)
       end

lib/new_relic/agent/transaction/trace_context.rb

@@ -190,10 +190,7 @@ def set_priority_and_sampled(sampler, ratio, payload)
             transaction.sampled = false
             transaction.priority = 0
           when 'trace_id_ratio_based'
-            upper_bound = (ratio * (2**64 - 1)).ceil
-            sampled = ratio == 1.0 || trace_id[8, 8].unpack1('Q>') < upper_bound
-
-            transaction.sampled = sampled
+            transaction.sampled = trace_ratio_sampled?(ratio)
             transaction.priority = adaptive_priority
           when 'adaptive'
             use_nr_tracestate_sampled(payload)