HDFS-7977. NFS couldn't take percentile intervals. Contributed by Brandon Li

(cherry picked from commit 570a83ae80faf2076966acf30588733803327844)
(cherry picked from commit 260dbe96c3d21ea372c728b2cd0f4a6aeb970010)

hadoop-hdfs-project/hadoop-hdfs-nfs/src/main/java/org/apache/hadoop/hdfs/nfs/conf/NfsConfigKeys.java

@@ -72,7 +72,6 @@ public class NfsConfigKeys {
   public static final String NFS_HTTPS_ADDRESS_DEFAULT = "0.0.0.0:" + NFS_HTTPS_PORT_DEFAULT;
   
   public static final String  NFS_METRICS_PERCENTILES_INTERVALS_KEY = "nfs.metrics.percentiles.intervals";
-  public static final String  NFS_METRICS_PERCENTILES_INTERVALS_DEFAULT = "";
   
   /*
    * HDFS super-user is the user with the same identity as NameNode process

hadoop-hdfs-project/hadoop-hdfs-nfs/src/main/java/org/apache/hadoop/hdfs/nfs/nfs3/Nfs3Metrics.java

@@ -90,9 +90,9 @@ public class Nfs3Metrics {
       readNanosQuantiles[i] = registry.newQuantiles("readProcessNanos"
           + interval + "s", "Read process in ns", "ops", "latency", interval);
       writeNanosQuantiles[i] = registry.newQuantiles("writeProcessNanos"
-          + interval + "s", " process in ns", "ops", "latency", interval);
+          + interval + "s", "Write process in ns", "ops", "latency", interval);
       commitNanosQuantiles[i] = registry.newQuantiles("commitProcessNanos"
-          + interval + "s", "Read process in ns", "ops", "latency", interval);
+          + interval + "s", "Commit process in ns", "ops", "latency", interval);
     }
   }
 
@@ -101,10 +101,9 @@ public class Nfs3Metrics {
     MetricsSystem ms = DefaultMetricsSystem.instance();
     JvmMetrics jm = JvmMetrics.create(gatewayName, sessionId, ms);
 
-    // Percentile measurement is [,,,] by default 
-    int[] intervals = conf.getInts(conf.get(
-        NfsConfigKeys.NFS_METRICS_PERCENTILES_INTERVALS_KEY,
-        NfsConfigKeys.NFS_METRICS_PERCENTILES_INTERVALS_DEFAULT));
+    // Percentile measurement is [50th,75th,90th,95th,99th] currently 
+    int[] intervals = conf
+        .getInts(NfsConfigKeys.NFS_METRICS_PERCENTILES_INTERVALS_KEY);
     return ms.register(new Nfs3Metrics(gatewayName, sessionId, intervals, jm));
   }
   
@@ -217,4 +216,4 @@ public class Nfs3Metrics {
     }
   }
 
-}
+}

hadoop-hdfs-project/hadoop-hdfs/CHANGES.txt

@@ -927,6 +927,8 @@ Release 2.7.0 - UNRELEASED
 
     HDFS-7961. Trigger full block report after hot swapping disk. (Eddy Xu via wang)
 
+    HDFS-7977. NFS couldn't take percentile intervals (brandonli)
+
     BREAKDOWN OF HDFS-7584 SUBTASKS AND RELATED JIRAS
 
       HDFS-7720. Quota by Storage Type API, tools and ClientNameNode

hadoop-hdfs-project/hadoop-hdfs/src/site/markdown/HdfsNfsGateway.md

@@ -170,6 +170,18 @@ It's strongly recommended for the users to update a few configuration properties
           <value>the_name_of_hdfs_superuser</value>
         </property>
 
+*   Metrics. Like other HDFS daemons, the gateway exposes runtime metrics. It is available at `http://gateway-ip:50079/jmx` as a JSON document.
+    The NFS handler related metrics is exposed under the name "Nfs3Metrics". The latency histograms can be enabled by adding the following
+    property to hdfs-site.xml file.
+
+        <property>
+          <name>nfs.metrics.percentiles.intervals</name>
+          <value>100</value>
+          <description>Enable the latency histograms for read, write and
+             commit requests. The time unit is 100 seconds in this example.
+          </description>
+        </property>
+
 *   JVM and log settings. You can export JVM settings (e.g., heap size and GC log) in
     HADOOP\_NFS3\_OPTS. More NFS related settings can be found in hadoop-env.sh.
     To get NFS debug trace, you can edit the log4j.property file