[WIP] Add ActiveRecord SQL caller stack

lib/ddtrace/contrib/active_record/events/sql.rb

@@ -26,6 +26,7 @@ def span_name
           end
 
           def process(span, event, _id, payload)
+            caller_path = Utils.extract_caller_path(caller)
             config = Utils.connection_config(payload[:connection], payload[:connection_id])
             settings = Datadog.configuration[:active_record, config]
             adapter_name = Datadog::Utils::Database.normalize_vendor(config[:adapter])
@@ -56,6 +57,7 @@ def process(span, event, _id, payload)
             span.set_tag(Ext::TAG_DB_VENDOR, adapter_name)
             span.set_tag(Ext::TAG_DB_NAME, config[:database])
             span.set_tag(Ext::TAG_DB_CACHED, cached) if cached
+            span.set_tag(Ext::SPAN_CALLER_STACK, caller_path) if caller_path.present?  # Only supported under Rails
             span.set_tag(Datadog::Ext::NET::TARGET_HOST, config[:host]) if config[:host]
             span.set_tag(Datadog::Ext::NET::TARGET_PORT, config[:port]) if config[:port]
           rescue StandardError => e

lib/ddtrace/contrib/active_record/ext.rb

@@ -10,6 +10,7 @@ module Ext
         ENV_ANALYTICS_SAMPLE_RATE = 'DD_TRACE_ACTIVE_RECORD_ANALYTICS_SAMPLE_RATE'.freeze
         ENV_ANALYTICS_SAMPLE_RATE_OLD = 'DD_ACTIVE_RECORD_ANALYTICS_SAMPLE_RATE'.freeze
         SERVICE_NAME = 'active_record'.freeze
+        SPAN_CALLER_STACK = 'active_record.query_caller_stack'.freeze
         SPAN_INSTANTIATION = 'active_record.instantiation'.freeze
         SPAN_SQL = 'active_record.sql'.freeze
         SPAN_TYPE_INSTANTIATION = 'custom'.freeze

lib/ddtrace/contrib/active_record/utils.rb

@@ -117,6 +117,17 @@ def self.db_config(connection_pool)
             connection_pool.spec.config
           end
         end
+
+        def self.extract_caller_path(callers)
+          return nil unless defined?(::Rails)
+
+          caller_path = callers
+                        .select { |c| c =~ /^#{::Rails.root}/ }
+                        .map { |c| c.gsub ::Rails.root.to_s, '' }[0...5]
+          # Handle cases when the db query is triggered from inside of a Rubygem
+          caller_path = callers[0...5] if caller_path.nil?
+          caller_path.join(",\n")
+        end
       end
     end
   end

spec/ddtrace/contrib/sinatra/activerecord_spec.rb

@@ -96,6 +96,9 @@ def migrate_db
       expect(sqlite_span.get_tag('active_record.db.name')).to eq(':memory:')
       expect(sqlite_span.get_tag('out.host')).to eq(adapter_host.to_s) unless adapter_host.nil?
       expect(sqlite_span.get_tag('out.port')).to eq(adapter_port.to_s) unless adapter_port.nil?
+      expect(
+        sqlite_span.get_tag('active_record.query_caller_stack').split("\n").size
+      ).to eq(5)
       expect(sqlite_span.span_type).to eq(Datadog::Ext::SQL::TYPE)
       expect(sqlite_span).to_not have_error
       expect(sqlite_span.parent).to eq(route_span)