HBASE-26432 enabled tracing from shell

hbase-shell/src/main/ruby/shell/commands/trace.rb

@@ -17,17 +17,12 @@
 # limitations under the License.
 #
 
-# Disable tracing for now as HTrace does not work any more
-#java_import org.apache.hadoop.hbase.trace.SpanReceiverHost
-
 module Shell
   module Commands
     class Trace < Command
-#      @@conf = org.apache.htrace.core.HTraceConfiguration.fromKeyValuePairs(
-#        'sampler.classes', 'org.apache.htrace.core.AlwaysSampler'
-#      )
-#      @@tracer = org.apache.htrace.core.Tracer::Builder.new('HBaseShell').conf(@@conf).build()
-#      @@tracescope = nil
+        @@tracer = org.apache.hadoop.hbase.trace.TraceUtil.getGlobalTracer()
+        @@tracespan = nil
+        @@tracescope = nil
 
       def help
         <<-EOF
@@ -58,23 +53,24 @@ def command(startstop = 'status', spanname = 'HBaseShell')
       end
 
       def trace(startstop, spanname)
-#        @@receiver ||= SpanReceiverHost.getInstance(@shell.hbase.configuration)
-#        if startstop == 'start'
-#          unless tracing?
-#            @@tracescope = @@tracer.newScope(spanname)
-#          end
-#        elsif startstop == 'stop'
-#          if tracing?
-#            @@tracescope.close
-#            @@tracescope = nil
-#          end
-#        end
-#        tracing?
+        if startstop == 'start'
+          unless tracing?
+           @@tracespan = @@tracer.spanBuilder(spanname).startSpan()
+           @@tracescope = @@tracespan.makeCurrent()
+          end
+        elsif startstop == 'stop'
+          if tracing?
+           @@tracescope.close()
+           @@tracespan.end()
+           @@tracescope = nil
+          end
+        end
+        tracing?
       end
 
-#      def tracing?
-#        @@tracescope != nil
-#      end
+      def tracing?
+        @@tracescope != nil
+      end
     end
   end
 end