HBASE-6449 added support for tracing requests through HBase, using the open source tracing library, 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).

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: This method serves as a callback whenever a span is completed. HTrace allows you to use as many SpanReceivers as you want so you can easily send trace information to multiple destinations. Configure what SpanReceivers you'd like to us by putting a comma separated list of the fully-qualified class name of classes implementing SpanReceiver in hbase-site.xml property: hbase.trace.spanreceiver.classes. HTrace includes a LocalFileSpanReceiver that writes all span information to local files in a JSON-based format. The LocalFileSpanReceiver looks in hbase-site.xml for a hbase.local-file-span-receiver.path property with a value describing the name of the file to which nodes should write their span information. hbase.trace.spanreceiver.classes org.htrace.impl.LocalFileSpanReceiver hbase.local-file-span-receiver.path /var/log/hbase/htrace.out ]]> HTrace also provides ZipkinSpanReceiver which converts spans to 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. 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. hbase.trace.spanreceiver.classes org.htrace.impl.ZipkinSpanReceiver hbase.zipkin.collector-hostname localhost hbase.zipkin.collector-port 9410 ]]> 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 HTrace.

In order to turn on tracing in your client code, you must initialize the module sending spans to receiver once per client process. Then you simply start tracing span before requests you think are interesting, and close it when the request is done. For example, if you wanted to trace all of your get operations, you change this: into: If you wanted to trace half of your 'get' operations, you would pass in: in lieu of Sampler.ALWAYS to Trace.startSpan(). See the HTrace README for more information on Samplers.

You can use trace command for tracing requests from HBase Shell. trace 'start' command turns on tracing and trace 'stop' command turns off tracing. trace 'start' hbase(main):002:0> put 'test', 'row1', 'f:', 'val1' # traced commands hbase(main):003:0> trace 'stop' ]]> trace 'start' and trace 'stop' always returns boolean value representing if or not there is ongoing tracing. As a result, trace 'stop' returns false on suceess. trace 'status' just returns if or not tracing is turned on. trace 'start' => true hbase(main):002:0> trace 'status' => true hbase(main):003:0> trace 'stop' => false hbase(main):004:0> trace 'status' => false ]]>