Re: [PR] HDDS-15093. Make RackScatter intra-rack placement capacity-aware [ozone]

["jojochuang (via GitHub)" <gi...@apache.org>]

jojochuang commented on code in PR #10648:
URL: https://github.com/apache/ozone/pull/10648#discussion_r3574814792


##########
hadoop-hdds/server-scm/src/test/java/org/apache/hadoop/hdds/scm/container/placement/algorithms/TestSCMContainerPlacementRackScatter.java:
##########
@@ -900,6 +919,34 @@ public void testAllNodesOnRackExcludedReducesRackCount2()
     assertEquals(1, chosenNodes.size());
   }
 
+  /**
+   * Within a single rack holding an emptier and a fuller datanode, the intra
+   * rack selection should prefer the less utilized node instead of choosing
+   * uniformly at random.
+   */
+  @Test
+  public void chooseNodeWithinRackPrefersLessUtilized() throws SCMException {
+    // Single rack with two datanodes.
+    setup(2, 2);
+    updateStorageInDatanode(0, 10, 90);   // emptier node
+    updateStorageInDatanode(1, 90, 10);   // fuller node
+
+    Map<DatanodeDetails, Integer> selectedCount = new HashMap<>();
+    selectedCount.put(datanodes.get(0), 0);
+    selectedCount.put(datanodes.get(1), 0);
+
+    for (int i = 0; i < 1000; i++) {

Review Comment:
   A thousand times seems too much for a simple test. For the sake of saving test run time, let's just run it 100 times:
   
   ```suggestion
       for (int i = 0; i < 100; i++) {
   ```



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