8000 HDFS-17049. EC: Fix duplicate block group IDs generated by SequentialBlockGroupIdGenerator. by zhangshuyan0 · Pull Request #5743 · apache/hadoop · GitHub
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HDFS-17049. EC: Fix duplicate block group IDs generated by SequentialBlockGroupIdGenerator. #5743

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HDFS-17049. EC: Fix duplicate block group IDs generated by SequentialBlockGroupIdGenerator. #5743

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HDFS-17049. EC: Fix duplicate block group IDs generated by Sequential…
zhangshuyan0 Jun 14, 2023
927cb4b
feedback review.
zhangshuyan0 Jun 14, 2023
5de876c
add some comments.
zhangshuyan0 Jun 14, 2023
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2 changes: 1 addition & 1 deletion ...n/java/org/apache/hadoop/hdfs/server/blockmanagement/SequentialBlockGroupIdGenerator.java
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Original file line number Diff line number Diff line change
Expand Up @@ -51,7 +51,7 @@ public class SequentialBlockGroupIdGenerator extends SequentialNumber {
}

@Override // NumberGenerator
public long nextValue() {
public synchronized long nextValue() {
skipTo((getCurrentValue() & ~BLOCK_GROUP_INDEX_MASK) + MAX_BLOCKS_IN_GROUP);
// Make sure there's no conflict with existing random block IDs
final Block b = new Block(getCurrentValue());
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41 changes: 41 additions & 0 deletions ...c/test/java/org/apache/hadoop/hdfs/server/blockmanagement/TestSequentialBlockGroupId.java
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Expand Up @@ -22,11 +22,15 @@
import static org.hamcrest.CoreMatchers.is;
import static org.hamcrest.CoreMatchers.not;
import static org.junit.Assert.assertThat;
import static org.junit.Assert.fail;
import static org.mockito.Mockito.doAnswer;
import static org.mockito.Mockito.spy;

import java.io.IOException;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
Expand Down Expand Up @@ -172,6 +176,43 @@ public void testTriggerBlockGroupIdCollision() throws IOException {
}
}

/**
* Test that the values generated by blockGroup ID generator are unique,
* even if they are generated concurrently.
* @throws Exception
*/
@Test
public void testBlockGroupIdThreadSafety() throws Exception {
// Each thread use a list to store its own block group IDs.
List<List<Long>> blockIds = new ArrayList<>();
List<Thread> threads = new ArrayList<>();

for (int i = 0; i < 20; i++) {
blockIds.add(new ArrayList<>());
threads.add(new Thread(() -> {
for (int j = 0; j < 1000; j++) {
long next = blockGrpIdGenerator.nextValue();
blockIds.get(j).add(next);
}
}));
}
for (Thread t : threads) {
t.start();
}
for (Thread t : threads) {
t.join();
}
// Check if there are duplicate IDs.
Set<Long> allBlockIds = new HashSet<>();
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Here will be more readable?

    Set<Long> allBlockIds = new HashSet<>();
    for (List<Long> set : blockIds) {
      for (long id : set) {
        if (!allBlockIds.add(id)) {
          fail("Same block group id is generated!");
        }
      }
    }

Any more simple check way? Such as using HashMap directly?

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Sorry I'm not understand how to use HashMap to get a more simple implement. I just modified the code as you did above.

for (List<Long> set : blockIds) {
for (long id : set) {
if (!allBlockIds.add(id)) {
fail("Same block group id is generated!");
}
}
}
}

/**
* Test that collisions in the blockGroup ID when the id is occupied by legacy
* block.
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