anchor.diff:  :icons: font
   :experimental:
   
  -link:https://issues.apache.org/jira/browse/HBASE-6449[HBASE-6449] added support for tracing requests through HBase, using the open source tracing library, link:http://github.com/cloudera/htrace[HTrace].
  +link:https://issues.apache.org/jira/browse/HBASE-6449[HBASE-6449] added support for tracing requests through HBase, using the open source tracing library, link:http://htrace.incubator.apache.org/[HTrace].
   Setting up tracing is quite simple, however it currently requires some very minor changes to your client code (it would not be very difficult to remove this requirement). 
   
   [[tracing.spanreceivers]]
   === SpanReceivers
   
  -The tracing system works by collecting information in structs called 'Spans'. It is up to you to choose how you want to receive this information by implementing the `SpanReceiver` interface, which defines one method: 
  +The tracing system works by collecting information in structures called 'Spans'. It is up to you to choose how you want to receive this information by implementing the `SpanReceiver` interface, which defines one method: 
   
   [source]
   ----
  
positive.code: 
  <property>
    <name>hbase.trace.spanreceiver.classes</name>
    <value>org.htrace.impl.LocalFileSpanReceiver</value>
  </property>
  <property>
    <name>hbase.local-file-span-receiver.path</name>
    <value>/var/log/hbase/htrace.out</value>
  </property>
  ----
  
  HTrace also provides `ZipkinSpanReceiver` which converts spans to link:http://github.com/twitter/zipkin[Zipkin] span format and send them to Zipkin server.
  In order to use this span receiver, you need to install the jar of htrace-zipkin to your HBase's classpath on all of the nodes in your cluster. 
  
  _htrace-zipkin_ is published to the maven central repository.
  You could get the latest version from there or just build it locally and then copy it out to all nodes, change your config to use zipkin receiver, distribute the new configuration and then (rolling) restart. 
  
  Here is the example of manual setup procedure. 
  
  ----
  
  $ git clone https://github.com/cloudera/htrace
  $ cd htrace/htrace-zipkin
  $ mvn compile assembly:single
  $ cp target/htrace-zipkin-*-jar-with-dependencies.jar $HBASE_HOME/lib/
    # copy jar to all nodes...
  ----
  
  The `ZipkinSpanReceiver` looks in _hbase-site.xml_      for a `hbase.zipkin.collector-hostname` and `hbase.zipkin.collector-port` property with a value describing the Zipkin collector server to which span information are sent. 
  
  [source,xml]
  ----
  
  <property>
    <name>hbase.trace.spanreceiver.classes</name>
    <value>org.htrace.impl.ZipkinSpanReceiver</value>
  </property> 
  <property>
    <name>hbase.zipkin.collector-hostname</name>
    <value>localhost</value>
  </property> 
  <property>
    <name>hbase.zipkin.collector-port</name>
    <value>9410</value>
  </property>
  ----
  
  If you do not want to use the included span receivers, you are encouraged to write your own receiver (take a look at `LocalFileSpanReceiver` for an example). If you think others would benefit from your receiver, file a JIRA or send a pull request to link:http://github.com/cloudera/htrace[HTrace]. 
  
  [[tracing.client.modifications]]
  == Client Modifications
  
negative.code: [[tracing.client.shell]]
  == Tracing from HBase Shell
  
  You can use `trace` command for tracing requests from HBase Shell. `trace 'start'` command turns on tracing and `trace 'stop'` command turns off tracing. 
  
  [source]
  ----
  