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https://issues.apache.org/jira/browse/HDFS-17049?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17732436#comment-17732436
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ASF GitHub Bot commented on HDFS-17049:
---------------------------------------

zhangshuyan0 commented on code in PR #5743:
URL: https://github.com/apache/hadoop/pull/5743#discussion_r1229201352


##########
hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/blockmanagement/SequentialBlockGroupIdGenerator.java:
##########
@@ -51,7 +51,7 @@ public class SequentialBlockGroupIdGenerator extends 
SequentialNumber {
   }
 
   @Override // NumberGenerator
-  public long nextValue() {
+  synchronized public long nextValue() {

Review Comment:
   Fixed.





> 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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