[GitHub] [hadoop] zhengchenyu commented on a diff in pull request #4127: HDFS-13522. RBF: Support observer node from Router-Based Federation

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

zhengchenyu commented on code in PR #4127:
URL: https://github.com/apache/hadoop/pull/4127#discussion_r893040886


##########
hadoop-hdfs-project/hadoop-hdfs-rbf/src/main/java/org/apache/hadoop/hdfs/server/federation/resolver/MembershipNamenodeResolver.java:
##########
@@ -371,24 +405,37 @@ private List<MembershipState> getRecentRegistrationForQuery(
         membershipStore.getNamenodeRegistrations(request);
 
     List<MembershipState> memberships = response.getNamenodeMemberships();
-    if (!addExpired || !addUnavailable) {
-      Iterator<MembershipState> iterator = memberships.iterator();
-      while (iterator.hasNext()) {
-        MembershipState membership = iterator.next();
-        if (membership.getState() == EXPIRED && !addExpired) {
-          iterator.remove();
-        } else if (membership.getState() == UNAVAILABLE && !addUnavailable) {
-          iterator.remove();
-        }
+    List<MembershipState> observerMemberships = new ArrayList<>();
+    Iterator<MembershipState> iterator = memberships.iterator();
+    while (iterator.hasNext()) {
+      MembershipState membership = iterator.next();
+      if (membership.getState() == EXPIRED && !addExpired) {
+        iterator.remove();
+      } else if (membership.getState() == UNAVAILABLE && !addUnavailable) {
+        iterator.remove();
+      } else if (membership.getState() == OBSERVER && observerRead) {
+        iterator.remove();
+        observerMemberships.add(membership);
       }
     }
 
-    List<MembershipState> priorityList = new ArrayList<>();
-    priorityList.addAll(memberships);
-    Collections.sort(priorityList, new NamenodePriorityComparator());
+    if(!observerRead) {
+      Collections.sort(memberships, new NamenodePriorityComparator());
+      LOG.debug("Selected most recent NN {} for query", memberships);
+      return  memberships;
+    } else {
+      List<MembershipState> ret = new ArrayList<>(
+          memberships.size() + observerMemberships.size());
+      Collections.sort(memberships, new NamenodePriorityComparator());
+      if(observerMemberships.size() > 1) {
+        Collections.shuffle(observerMemberships);

Review Comment:
   I think recently means the latest observer namenode set from MembershipState. Then disperse queries by shuffle.



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