[GitHub] [hadoop] ZanderXu commented on a diff in pull request #4990: HDFS-13507. RBF RouterAdmin disable update functionality in add cmd and supports add/update one mount table with different destination

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

ZanderXu commented on code in PR #4990:
URL: https://github.com/apache/hadoop/pull/4990#discussion_r994230000


##########
hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/tools/federation/RouterAdmin.java:
##########
@@ -147,13 +147,13 @@ private String getUsage(String cmd) {
       return usage.toString();
     }
     if (cmd.equals("-add")) {
-      return "\t[-add <source> <nameservice1, nameservice2, ...> <destination> "
+      return "\t[-add <source> <nameservice1, nameservice2, ...> <destination1, destination2, ...> "
           + "[-readonly] [-faulttolerant] "
           + "[-order HASH|LOCAL|RANDOM|HASH_ALL|SPACE] "
           + "-owner <owner> -group <group> -mode <mode>]";
     } else if (cmd.equals("-update")) {
       return "\t[-update <source>"
-          + " [<nameservice1, nameservice2, ...> <destination>] "
+          + " [<nameservice1, nameservice2, ...> <destination1, destination2, ...>] "

Review Comment:
   Sir, `<source> <nameservice1, nameservice2> <destination>` still works well right now. 
   If user inputed multiple destinations, the number of destinations should be equals with the number of namespace.
   
   ```
   private Map<String, String> getDestMap(String[] nss, String[] destinations)
         throws IOException {
       // It's ok if there is only one namespace and one destination.
       // It's ok if there are multiple namespaces and one destination.
       // It's ok if there are multiple namespaces and the same number of destinations.
       if (nss.length != destinations.length) {
         if (nss.length == 1 || destinations.length > 1) {
           String message = "Invalid namespaces and destinations."
               + " The number of destinations " + destinations.length
               + " is not matched with the number of namespaces " + nss.length;
           System.err.println(message);
           throw new IOException(message);
         }
       }
   
       Map<String, String> destMap = new LinkedHashMap<>();
       for (int index = 0; index < nss.length; index++) {
         int destIndex = destinations.length == 1 ? 0 : index;
         destMap.put(nss[index], destinations[destIndex]);
       }
       return destMap;
     }
   ```
   



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