HDFS-6717. JIRA HDFS-5804 breaks default nfs-gateway behavior for unsecured config. Contributed by Brandon Li

git-svn-id: https://svn.apache.org/repos/asf/hadoop/common/trunk@1614125 13f79535-47bb-0310-9956-ffa450edef68

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

@@ -938,6 +938,9 @@ Release 2.5.0 - UNRELEASED
     HDFS-6723. New NN webUI no longer displays decommissioned state for dead node.
     (Ming Ma via wheat9)
 
+    HDFS-6717. JIRA HDFS-5804 breaks default nfs-gateway behavior for unsecured config
+    (brandonli)
+
   BREAKDOWN OF HDFS-2006 SUBTASKS AND RELATED JIRAS
 
     HDFS-6299. Protobuf for XAttr and client-side implementation. (Yi Liu via umamahesh)

hadoop-hdfs-project/hadoop-hdfs/src/site/apt/HdfsNfsGateway.apt.vm

@@ -44,10 +44,13 @@ HDFS NFS Gateway
 
 * {Configuration}
 
-   The user running the NFS-gateway must be able to proxy all the users using the NFS mounts. 
-   For instance, if user 'nfsserver' is running the gateway, and users belonging to the groups 'nfs-users1'
-   and 'nfs-users2' use the NFS mounts, then in core-site.xml of the namenode, the following must be set
-   (NOTE: replace 'nfsserver' with the user name starting the gateway in your cluster):
+   The NFS-gateway uses proxy user to proxy all the users accessing the NFS mounts. 
+   In non-secure mode, the user running the gateway is the proxy user, while in secure mode the
+   user in Kerberos keytab is the proxy user. Suppose the proxy user is 'nfsserver'
+   and users belonging to the groups 'nfs-users1'
+   and 'nfs-users2' use the NFS mounts, then in core-site.xml of the NameNode, the following
+   two properities must be set and only NameNode needs restart after the configuration change
+   (NOTE: replace the string 'nfsserver' with the proxy user name in your cluster):
 
 ----
 <property>
@@ -72,7 +75,9 @@ HDFS NFS Gateway
 ----
 
    The above are the only required configuration for the NFS gateway in non-secure mode. For Kerberized
-   hadoop clusters, the following configurations need to be added to hdfs-site.xml:
+   hadoop clusters, the following configurations need to be added to hdfs-site.xml for the gateway (NOTE: replace 
+   string "nfsserver" with the proxy user name and ensure the user contained in the keytab is
+   also the same proxy user):
 
 ----
   <property>
@@ -87,6 +92,8 @@ HDFS NFS Gateway
     <value>nfsserver/_HOST@YOUR-REALM.COM</value>
   </property>
 ----
+  
+   The rest of the NFS gateway configurations are optional for both secure and non-secure mode.
 
    The AIX NFS client has a {{{https://issues.apache.org/jira/browse/HDFS-6549}few known issues}}
    that prevent it from working correctly by default with the HDFS NFS
@@ -108,7 +115,7 @@ HDFS NFS Gateway
    have been committed.
 
    It's strongly recommended for the users to update a few configuration properties based on their use
-   cases. All the related configuration properties can be added or updated in hdfs-site.xml.
+   cases. All the following configuration properties can be added or updated in hdfs-site.xml.
   
    * If the client mounts the export with access time update allowed, make sure the following 
     property is not disabled in the configuration file. Only NameNode needs to restart after 
@@ -145,36 +152,6 @@ HDFS NFS Gateway
   </property>
 ---- 
 
-   * For optimal performance, it is recommended that rtmax be updated to
-     1MB. However, note that this 1MB is a per client allocation, and not
-     from a shared memory pool, and therefore a larger value may adversely 
-     affect small reads, consuming a lot of memory. The maximum value of 
-     this property is 1MB.
-
-----
-<property>
-  <name>nfs.rtmax</name>
-  <value>1048576</value>
-  <description>This is the maximum size in bytes of a READ request
-    supported by the NFS gateway. If you change this, make sure you
-    also update the nfs mount's rsize(add rsize= # of bytes to the 
-    mount directive).
-  </description>
-</property>
-----
-
-----
-<property>
-  <name>nfs.wtmax</name>
-  <value>65536</value>
-  <description>This is the maximum size in bytes of a WRITE request
-    supported by the NFS gateway. If you change this, make sure you
-    also update the nfs mount's wsize(add wsize= # of bytes to the 
-    mount directive).
-  </description>
-</property>
-----
-
   * By default, the export can be mounted by any client. To better control the access,
     users can update the following property. The value string contains machine name and
     access privilege, separated by whitespace
@@ -238,8 +215,10 @@ HDFS NFS Gateway
 
    [[3]] Start mountd and nfsd.
    
-     No root privileges are required for this command. However, ensure that the user starting
-     the Hadoop cluster and the user starting the NFS gateway are same.
+     No root privileges are required for this command. In non-secure mode, the NFS gateway
+     should be started by the proxy user mentioned at the beginning of this user guide. 
+     While in secure mode, any user can start NFS gateway 
+     as long as the user has read access to the Kerberos keytab defined in "nfs.keytab.file".
 
 -------------------------
      hadoop nfs3
@@ -339,7 +318,10 @@ HDFS NFS Gateway
 -------------------------------------------------------------------
 
   Then the users can access HDFS as part of the local file system except that, 
-  hard link and random write are not supported yet.
+  hard link and random write are not supported yet. To optimize the performance
+  of large file I/O, one can increase the NFS transfer size(rsize and wsize) during mount.
+  By default, NFS gateway supports 1MB as the maximum transfer size. For larger data
+  transfer size, one needs to update "nfs.rtmax" and "nfs.rtmax" in hdfs-site.xml.
 
 * {Allow mounts from unprivileged clients}