HDFS-17488. DN can fail IBRs with NPE when a volume is removed #6759
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Hi @ZanderXu @Hexiaoqiao, can you help me take a look whenever you're free? Thanks! |
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Apr 23, 2024
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Thanks @kokonguyen191 for your report. It's a nice catch.
Leave some comments, thanks
| final ReceivedDeletedBlockInfo[] rdbi = perStorage.removeAll(); | ||
| if (rdbi != null) { | ||
| reports.add(new StorageReceivedDeletedBlocks(entry.getKey(), rdbi)); | ||
| if (rdbi == null) { |
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if (rdbi != null) {
// Null storage, should not happen
if (entry.getKey() == null) {
dnMetrics.incrNullStorageBlockReports();
continue;
}
reports.add(new StorageReceivedDeletedBlocks(entry.getKey(), rdbi));
}
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I intentionally put it like this to reduce nesting and make the logic a bit easier to read
| return pendingIBRs.size(); | ||
| } | ||
| } | ||
| } |
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Done. Actually took me quite a while to find the setting to disable it in IDE
| // Block is not finalized - ignore the difference | ||
| return; | ||
| } | ||
| if (!storageMap.containsKey(storageUuid)) { |
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How about moving this logic to line 2750？
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Moved the block up
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Apr 28, 2024
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Thanks @kokonguyen191 . LGTM
haiyang1987
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Apr 28, 2024
...project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/BPOfferService.java
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@kokonguyen191 Thanks for your report and contributions. Sorry didn't get this issue completely. Another side, you mentioned that this issue is triggered by volume removed, so how the logic between volume removed to NPE. Thanks again. |
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Hi @Hexiaoqiao, thanks for the review. For your first question, |
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@Hexiaoqiao Hi, sir. please take a look at the description of #6730 . I found the same problem and explained in that PR's description. |
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May 6, 2024
...adoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/metrics/DataNodeMetrics.java
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LGTM. Hi @Hexiaoqiao @hfutatzhanghb any other comments? |
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Merged. Thanks @kokonguyen191 for your contribution and thanks @Hexiaoqiao @haiyang1987 @hfutatzhanghb for your review. |
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Description of PR
Error logs
The root cause is in
BPOfferService#notifyNamenodeBlock, happens when it's called on a block belonging to a volume already removed prior. Because the volume was already removedso IBRs with a null storage are now pending.
The reason why notifyNamenodeBlock can trigger on such blocks is up in DirectoryScanner#reconcile
Inside
checkAndUpdate,memBlockInfois null because all the block meta in memory is removed during the volume removal, butdiskFilestill exists. ThenDataNode#notifyNamenodeDeletedBlock(and further down the line,notifyNamenodeBlock) is called on this block.This patch effectively contains 2 parts:
FsDatasetImpl#checkAndUpdatefrom running on a block belonging to a removed storageHow was this patch tested?
Unit tests. Partially on production cluster.
For code changes: