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Posted to dev@flink.apache.org by "Rui Fan (Jira)" <ji...@apache.org> on 2022/12/20 11:17:00 UTC

[jira] [Created] (FLINK-30461) Some rocksdb sst files will remain forever

Rui Fan created FLINK-30461:
-------------------------------

             Summary: Some rocksdb sst files will remain forever
                 Key: FLINK-30461
                 URL: https://issues.apache.org/jira/browse/FLINK-30461
             Project: Flink
          Issue Type: Bug
          Components: Runtime / Checkpointing
    Affects Versions: 1.15.3, 1.16.0, 1.17.0
            Reporter: Rui Fan
         Attachments: image-2022-12-20-18-45-32-948.png, image-2022-12-20-18-47-42-385.png

In rocksdb incremental checkpoint mode, during file upload, if some files have been uploaded and some files have not been uploaded, the checkpoint timeout is canceled at this time, and the uploaded files will remain.

 
h2. Impact: 

The shared directory of a flink job has more than 1 million files. It exceeded the hdfs upper limit, causing new files not to be written.

However only 50k files are available, the other 950k files should be cleaned up.

!https://user-images.githubusercontent.com/38427477/207588272-dda7ba69-c84c-4372-aeb4-c54657b9b956.png|width=1962,height=364!
h2. Root cause:

If an exception is thrown during the checkpoint async phase, flink will clean up metaStateHandle, miscFiles and sstFiles.

However, when all sst files are uploaded, they are added together to sstFiles. If some sst files have been uploaded and some sst files are still being uploaded, and the checkpoint timeout is canceled at this time, all sst files will not be added to sstFiles. The uploaded sst will remain on hdfs.

[code link|https://github.com/apache/flink/blob/49146cdec41467445de5fc81f100585142728bdf/flink-state-backends/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/snapshot/RocksIncrementalSnapshotStrategy.java#L328]
h2. Solution:

Using the CloseableRegistry as the tmpResourcesRegistry. If the async phase is failed, the tmpResourcesRegistry will cleanup these temporary resources.

 

POC code:

https://github.com/1996fanrui/flink/commit/86a456b2bbdad6c032bf8e0bff71c4824abb3ce1

 

 

!image-2022-12-20-18-45-32-948.png|width=1114,height=442!

!image-2022-12-20-18-47-42-385.png|width=1332,height=552!

 



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