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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