[GitHub] [hbase] clarax commented on a change in pull request #3723: HBASE-26309 Balancer tends to move regions to the server at the end o…

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clarax commented on a change in pull request #3723:
URL: https://github.com/apache/hbase/pull/3723#discussion_r740344466



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File path: hbase-balancer/src/main/java/org/apache/hadoop/hbase/master/balancer/LoadCandidateGenerator.java
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@@ -34,27 +35,51 @@ BalanceAction generate(BalancerClusterState cluster) {
   private int pickLeastLoadedServer(final BalancerClusterState cluster, int thisServer) {
     Integer[] servers = cluster.serverIndicesSortedByRegionCount;
 
-    int index = 0;
-    while (servers[index] == null || servers[index] == thisServer) {
-      index++;
-      if (index == servers.length) {
-        return -1;
+    int selectedIndex = -1;
+    double currentLargestRandom = -1;
+    for (int i = 0; i < servers.length; i++) {
+      if (servers[i] == null || servers[i] == thisServer) {
+        continue;
+      }
+      if (selectedIndex != -1
+        && cluster.getNumRegionsComparator().compare(servers[i], servers[selectedIndex]) != 0) {
+        // Exhausted servers of the same region count
+        break;
+      }
+      // we don't know how many servers have the same region count, we will randomly select one

Review comment:
       @Apache9 Thank you for checking the code and reference. Yes, this is a in place random selection for stream data. Updating the comments. 




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