HBASE-9985 Add HBase shell command to start/stop tracing

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@1542894 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -0,0 +1,76 @@
+#
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+HTrace = org.cloudera.htrace.Trace
+java_import org.cloudera.htrace.Sampler
+java_import org.apache.hadoop.hbase.trace.SpanReceiverHost
+
+module Shell
+  module Commands
+    class Trace < Command
+      def help
+        return <<-EOF
+Start or Stop tracing using HTrace.
+Always returns true if tracing is running, otherwise false.
+If the first argument is 'start', new span is started.
+If the first argument is 'stop', current running span is stopped.
+('stop' returns false on success.)
+If the first argument is 'status', just returns if or not tracing is running.
+On 'start'-ing, you can optionally pass the name of span as the second argument.
+The default name of span is 'HBaseShell'.
+Repeating 'start' does not start nested span.
+
+Examples:
+
+  hbase> trace 'start'
+  hbase> trace 'status'
+  hbase> trace 'stop'
+
+  hbase> trace 'start', 'MySpanName'
+  hbase> trace 'stop'
+
+EOF
+      end
+
+      def command(startstop="status", spanname="HBaseShell")
+        format_and_return_simple_command do 
+          trace(startstop, spanname)
+        end
+      end
+
+      def trace(startstop, spanname)
+        @@receiver ||= SpanReceiverHost.getInstance(@shell.hbase.configuration)
+        if startstop == "start"
+          if not tracing?
+            @@tracescope = HTrace.startSpan(spanname, Sampler.ALWAYS)
+          end
+        elsif startstop == "stop"
+          if tracing?
+            @@tracescope.close()
+          end
+        end
+        tracing?
+      end
+
+      def tracing?()
+        HTrace.isTracing()
+      end
+
+    end
+  end
+end