HADOOP-13839. Fix outdated tracing documentation. Contributed by Elek, Marton.

hadoop-common-project/hadoop-common/CHANGES.txt

@@ -107,6 +107,9 @@ Release 2.7.4 - UNRELEASED
     HADOOP-11859. PseudoAuthenticationHandler fails with httpcomponents v4.4.
     (Eugene Koifman via jitendra)
 
+    HADOOP-13839. Fix outdated tracing documentation.
+    (Elek, Marton via iwasakims)
+
 Release 2.7.3 - 2016-08-25
 
   INCOMPATIBLE CHANGES

hadoop-common-project/hadoop-common/src/site/markdown/Tracing.md

@@ -12,6 +12,7 @@
   limitations under the License. See accompanying LICENSE file.
 -->
 
+
 Enabling Dapper-like Tracing in Hadoop
 ======================================
 
@@ -24,7 +25,8 @@ Enabling Dapper-like Tracing in Hadoop
         * [Dynamic update of tracing configuration](#Dynamic_update_of_tracing_configuration)
         * [Starting tracing spans by HTrace API](#Starting_tracing_spans_by_HTrace_API)
         * [Sample code for tracing](#Sample_code_for_tracing)
-  
+
+
 Dapper-like Tracing in Hadoop
 -----------------------------
 
@@ -37,14 +39,14 @@ Setting up tracing is quite simple, however it requires some very minor changes
 
 ### Samplers
 
-Configure the samplers in `core-site.xml` property: `hadoop.htrace.sampler`.
+Configure the samplers in `core-site.xml` property: `dfs.htrace.sampler`.
 The value can be NeverSampler, AlwaysSampler or ProbabilitySampler.
 NeverSampler: HTrace is OFF for all spans;
 AlwaysSampler: HTrace is ON for all spans;
 ProbabilitySampler: HTrace is ON for some percentage% of top-level spans.
 
       <property>
-        <name>hadoop.htrace.sampler</name>
+        <name>dfs.htrace.sampler</name>
         <value>NeverSampler</value>
       </property>
 
@@ -61,18 +63,18 @@ by putting a comma separated list of the fully-qualified class name of classes i
 in `core-site.xml` property: `hadoop.htrace.spanreceiver.classes`.
 
       <property>
-        <name>hadoop.htrace.spanreceiver.classes</name>
+        <name>dfs.htrace.spanreceiver.classes</name>
         <value>org.apache.htrace.impl.LocalFileSpanReceiver</value>
       </property>
       <property>
-        <name>hadoop.htrace.local-file-span-receiver.path</name>
+        <name>dfs.htrace.local-file-span-receiver.path</name>
         <value>/var/log/hadoop/htrace.out</value>
       </property>
 
 You can omit package name prefix if you use span receiver bundled with HTrace.
 
       <property>
-        <name>hadoop.htrace.spanreceiver.classes</name>
+        <name>dfs.htrace.spanreceiver.classes</name>
         <value>LocalFileSpanReceiver</value>
       </property>
 
@@ -83,30 +85,32 @@ you can use `ZipkinSpanReceiver` which uses
 [Zipkin](https://github.com/twitter/zipkin) for collecting and displaying tracing data.
 
 In order to use `ZipkinSpanReceiver`,
-you need to download and setup [Zipkin](https://github.com/twitter/zipkin) first.
+you need to download and setup [Zipkin](https://github.com/twitter/zipkin) first. With docker you can start an experimental zipkin server with the following command.
+
+```
+docker run -d -p 9411:9411 -p 9410:9410 openzipkin/zipkin
+```
 
 you also need to add the jar of `htrace-zipkin` to the classpath of Hadoop on each node.
-Here is example setup procedure.
+The easiest way to achieve this is downloading the binary jars from maven central add put it to the hadoop lib directory.
 
-      $ git clone https://github.com/cloudera/htrace
-      $ cd htrace/htrace-zipkin
-      $ mvn compile assembly:single
-      $ cp target/htrace-zipkin-*-jar-with-dependencies.jar $HADOOP_HOME/share/hadoop/common/lib/
+    $ wget http://repo1.maven.org/maven2/org/apache/thrift/libthrift/0.9.0/libthrift-0.9.0.jar -O $HADOOP_HOME/share/hadoop/common/lib/libthrift-0.9.0.jar
+    $ wget http://repo1.maven.org/maven2/org/apache/htrace/htrace-zipkin/3.1.0-incubating/htrace-zipkin-3.1.0-incubating.jar -O $HADOOP_HOME/share/hadoop/common/lib/htrace-zipkin-3.1.0-incubating.jar
 
 The sample configuration for `ZipkinSpanReceiver` is shown below.
 By adding these to `core-site.xml` of NameNode and DataNodes, `ZipkinSpanReceiver` is initialized on the startup.
 You also need this configuration on the client node in addition to the servers.
 
       <property>
-        <name>hadoop.htrace.spanreceiver.classes</name>
+        <name>dfs.htrace.spanreceiver.classes</name>
         <value>ZipkinSpanReceiver</value>
       </property>
       <property>
-        <name>hadoop.htrace.zipkin.collector-hostname</name>
+        <name>dfs.htrace.zipkin.collector-hostname</name>
         <value>192.168.1.2</value>
       </property>
       <property>
-        <name>hadoop.htrace.zipkin.collector-port</name>
+        <name>dfs.htrace.zipkin.collector-port</name>
         <value>9410</value>
       </property>
 
@@ -136,8 +140,8 @@ You need to run the command against all servers if you want to update the config
 You need to specify the class name of span receiver as argument of `-class` option.
 You can specify the configuration associated with span receiver by `-Ckey=value` options.
 
-      $ hadoop trace -add -class LocalFileSpanReceiver -Chadoop.htrace.local-file-span-receiver.path=/tmp/htrace.out -host 192.168.56.2:9000
-      Added trace span receiver 2 with configuration hadoop.htrace.local-file-span-receiver.path = /tmp/htrace.out
+      $ hadoop trace -add -class LocalFileSpanReceiver -Clocal-file-span-receiver.path=/tmp/htrace.out -host 192.168.56.2:9000
+      Added trace span receiver 2 with configuration local-file-span-receiver.path = /tmp/htrace.out
 
       $ hadoop trace -list -host 192.168.56.2:9000
       ID  CLASS
@@ -159,7 +163,7 @@ In addition, you need to initialize `SpanReceiver` once per process.
 
     ...
 
-        SpanReceiverHost.getInstance(new HdfsConfiguration());
+        SpanReceiverHost.get(new HdfsConfiguration(), "dfs");
 
     ...
 
@@ -189,7 +193,7 @@ which start tracing span before invoking HDFS shell command.
         FsShell shell = new FsShell();
         conf.setQuietMode(false);
         shell.setConf(conf);
-        SpanReceiverHost.getInstance(conf);
+        SpanReceiverHost.get(conf, "dfs");
         int res = 0;
         TraceScope ts = null;
         try {
@@ -207,3 +211,5 @@ You can compile and execute this code as shown below.
 
     $ javac -cp `hadoop classpath` TracingFsShell.java
     $ java -cp .:`hadoop classpath` TracingFsShell -ls /
+
+The configuration prefix for the client-side htrace configuration is defined in the SpanReceiverHost.get call. In the case above you should use the dfs prefix as on the server side. (*dfs*.htrace…. configuration values)