HADOOP-11544. Remove unused configuration keys for tracing. Contributed by Masatake Iwasaki.

(cherry picked from commit 42548f4dc2b2e8ace891b970c2c6712c02bb43ea)

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

@@ -169,6 +169,9 @@ Release 2.7.0 - UNRELEASED
     HADOOP-11442. hadoop-azure: Create test jar.
     (Shashank Khandelwal via cnauroth)
 
+    HADOOP-11544. Remove unused configuration keys for tracing. (Masatake
+    Iwasaki via aajisaka)
+
   OPTIMIZATIONS
 
     HADOOP-11323. WritableComparator#compare keeps reference to byte array.

hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/CommonConfigurationKeys.java

@@ -286,7 +286,4 @@ public class CommonConfigurationKeys extends CommonConfigurationKeysPublic {
   public static final String NFS_EXPORTS_ALLOWED_HOSTS_SEPARATOR = ";";
   public static final String NFS_EXPORTS_ALLOWED_HOSTS_KEY = "nfs.exports.allowed.hosts";
   public static final String NFS_EXPORTS_ALLOWED_HOSTS_KEY_DEFAULT = "* rw";
-
-  public static final String  HADOOP_TRACE_SAMPLER = "hadoop.htrace.sampler";
-  public static final String  HADOOP_TRACE_SAMPLER_DEFAULT = "NeverSampler";
 }

hadoop-common-project/hadoop-common/src/main/resources/core-default.xml

@@ -1646,18 +1646,6 @@ for ldap providers in the same way as above does.
   </description>
 </property>
 
-<property>
-  <name>hadoop.htrace.sampler</name>
-  <value>NeverSampler</value>
-  <description>
-    Configure the samplers for HTrace, 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.
-  </description>
-</property>
-
 <property>
   <name>hadoop.htrace.spanreceiver.classes</name>
   <value></value>