[GitHub] [hbase] huaxiangsun commented on a change in pull request #2652: HBASE-25280 [meta replicas] ArrayIndexOutOfBoundsException in ZKConne…

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huaxiangsun commented on a change in pull request #2652:
URL: https://github.com/apache/hbase/pull/2652#discussion_r522623604



##########
File path: hbase-client/src/main/java/org/apache/hadoop/hbase/client/ZKConnectionRegistry.java
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@@ -133,13 +133,17 @@ private static void tryComplete(MutableInt remaining, HRegionLocation[] locs,
       ServerName.valueOf(snProto.getHostName(), snProto.getPort(), snProto.getStartCode()));
   }
 
-  private void getMetaRegionLocation(CompletableFuture<RegionLocations> future,
+  @VisibleForTesting
+  void getMetaRegionLocation(CompletableFuture<RegionLocations> future,
       List<String> metaReplicaZNodes) {
     if (metaReplicaZNodes.isEmpty()) {
       future.completeExceptionally(new IOException("No meta znode available"));
     }
     HRegionLocation[] locs = new HRegionLocation[metaReplicaZNodes.size()];
     MutableInt remaining = new MutableInt(locs.length);
+    // Do NOT use replicaid as index into locations array. The location set may not be complete

Review comment:
       Based on Duo and Stack's comments, I spend quite some time trying to understand how `locs` is being used. 
   It is being used in 
   https://github.com/apache/hbase/blob/master/hbase-client/src/main/java/org/apache/hadoop/hbase/client/ZKConnectionRegistry.java#L162
   
   It is used for initialize RegionLocations() object. 
   Within RegionLocations(), all logic is there trying to allocate a location array with replica id as index.
   https://github.com/apache/hbase/blob/master/hbase-client/src/main/java/org/apache/hadoop/hbase/RegionLocations.java#L74
   
   So it seems that at least in this place, it is fine to do in this way. Otherwise, the logic is duplicated twice?
   
   
   




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