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https://issues.apache.org/jira/browse/HDFS-17049?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17732458#comment-17732458
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ASF GitHub Bot commented on HDFS-17049:
---------------------------------------
zhtttylz commented on PR #5743:
URL: https://github.com/apache/hadoop/pull/5743#issuecomment-1590809127
@zhangshuyan0 Thank you very much for your valuable time. I would like to
inquire about the concurrency issue in
**SequentialBlockGroupIdGenerator#nextValue**. It seems that
**FSNamesystem#nextBlockId** verifies **FSNamesystemLock#writeLock**.
```java
Block createNewBlock(BlockType blockType) throws IOException {
assert hasWriteLock();
Block b = new Block(nextBlockId(blockType), 0, 0);
// Increment the generation stamp for every new block.
b.setGenerationStamp(nextGenerationStamp(false));
return b;
}
```
> EC: Fix duplicate block group IDs generated by SequentialBlockGroupIdGenerator
> ------------------------------------------------------------------------------
>
> Key: HDFS-17049
> URL: https://issues.apache.org/jira/browse/HDFS-17049
> Project: Hadoop HDFS
> Issue Type: Bug
> Reporter: Shuyan Zhang
> Assignee: Shuyan Zhang
> Priority: Major
> Labels: pull-request-available
>
> When I used multiple clients to write EC files concurrently, I found that
> NameNode generated the same block group ID for different files:
> ```
> 2023-06-13 20:09:59,514 INFO org.apache.hadoop.hdfs.StateChange: BLOCK*
> allocate blk_-9223372036854697568_14389 for /ec-test/10/4068034329705654124
> 2023-06-13 20:09:59,514 INFO org.apache.hadoop.hdfs.StateChange: BLOCK*
> allocate blk_-9223372036854697568_14390 for /ec-test/19/7042966144171770731
> ```
> After diving into `SequentialBlockGroupIdGenerator`, I found that the current
> implementation of `nextValue` is not thread-safe.
> This problem must be fixed.
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