[GitHub] [hadoop] ZanderXu commented on a diff in pull request #5098: HDFS-16831. [RBF SBN] GetNamenodesForNameserviceId should shuffle Observer NameNodes every time

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

ZanderXu commented on code in PR #5098:
URL: https://github.com/apache/hadoop/pull/5098#discussion_r1017802115


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hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/resolver/MembershipNamenodeResolver.java:
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@@ -189,13 +189,45 @@ private void updateNameNodeState(final String nsId,
     }
   }
 
+  private <T extends FederationNamenodeContext> List<T> shuffleObserverNN(
+      List<T> inputNameNodes, boolean listObserversFirst) {
+    if (!listObserversFirst) {
+      return inputNameNodes;
+    }
+    // Get Observers first.
+    List<T> observerList = new ArrayList<>();
+    for (T t : inputNameNodes) {
+      if (t.getState() == OBSERVER) {
+        observerList.add(t);
+      } else {
+        // The inputNameNodes are already sorted, so it can break

Review Comment:
   Yes. If `listObserversFirst` is true, all Observers will be placed at the front of the `inputNameNodes` which been processed by `getRecentRegistrationForQuery` method.
   
   If we want to make this method more common, I can ignore it and loop all the inputNameNodes to find the Observers.



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