[GitHub] [hadoop] fengnanli commented on a change in pull request #2639: HDFS-15785. Datanode to support using DNS to resolve nameservices to IP addresses to get list of namenodes.

[GitBox <gi...@apache.org>]

fengnanli commented on a change in pull request #2639:
URL: https://github.com/apache/hadoop/pull/2639#discussion_r572411463



##########
File path: hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSConfigKeys.java
##########
@@ -1557,6 +1557,17 @@
   public static final double
       DFS_DATANODE_RESERVE_FOR_ARCHIVE_DEFAULT_PERCENTAGE_DEFAULT = 0.0;
 
+
+  public static final String
+      DFS_NAMESERVICES_RESOLUTION_ENABLED =

Review comment:
       Will these configs used by other services (JournalNode, ZKFC)? If not, can we specify the datanode in the prefix?

##########
File path: hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/DFSUtil.java
##########
@@ -647,6 +634,58 @@ public static String addKeySuffixes(String key, String... suffixes) {
       getNNLifelineRpcAddressesForCluster(Configuration conf)
       throws IOException {
 
+    Collection<String> parentNameServices = getParentNameServices(conf);
+
+    return getAddressesForNsIds(conf, parentNameServices, null,
+        DFS_NAMENODE_LIFELINE_RPC_ADDRESS_KEY);
+  }
+
+  //
+  /**
+   * Returns the configured address for all NameNodes in the cluster.
+   * This is similar with DFSUtilClient.getAddressesForNsIds()
+   * but can access DFSConfigKeys.
+   *
+   * @param conf configuration
+   * @param defaultAddress default address to return in case key is not found.
+   * @param keys Set of keys to look for in the order of preference
+   *
+   * @return a map(nameserviceId to map(namenodeId to InetSocketAddress))
+   */
+  static Map<String, Map<String, InetSocketAddress>> getAddressesForNsIds(

Review comment:
       Why adding this function here instead of changing the function in the DFSUtilClient.getAddressesForNsIds ?




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