[GitHub] [hadoop] zhtttylz commented on pull request #5759: HDFS-17052. Erasure coding reconstruction failed when num of storageT…

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

zhtttylz commented on PR #5759:
URL: https://github.com/apache/hadoop/pull/5759#issuecomment-1600330026

   
   ```java
    //BlockPlacementPolicyRackFaultTolerant#chooseEvenlyFromRemainingRacks
    int bestEffortMaxNodesPerRack = maxNodesPerRack;
    while (results.size() != totalReplicaExpected &&
           numResultsOflastChoose != results.size()) {
         // Exclude the chosen nodes
         final Set<Node> newExcludeNodes = new HashSet<>();
         for (DatanodeStorageInfo resultStorage : results) {
           addToExcludedNodes(resultStorage.getDatanodeDescriptor(),
               newExcludeNodes);
         }
   
         LOG.trace("Chosen nodes: {}", results);
         LOG.trace("Excluded nodes: {}", excludedNodes);
         LOG.trace("New Excluded nodes: {}", newExcludeNodes);
         final int numOfReplicas = totalReplicaExpected - results.size();
         numResultsOflastChoose = results.size();
         try {
           chooseOnce(numOfReplicas, writer, newExcludeNodes, blocksize,
               ++bestEffortMaxNodesPerRack, results, avoidStaleNodes,
               storageTypes);
         } catch (NotEnoughReplicasException nere) {
           lastException = nere;
         } finally {
           excludedNodes.addAll(newExcludeNodes);
         }
       }
   ```
   Since **totalNumOfReplicas < numOfRacks**, **maxNodesPerRack** initial to **1**. If after incrementing **bestEffortMaxNodesPerRack++**, **BlockPlacementPolicyRackFaultTolerant#chooseOnce** still cannot select a new node to add to the results, the 'while' loop will exit because **numResultsOflastChoose != results.size()** is **false**.


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