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https://issues.apache.org/jira/browse/FLINK-19016?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17197609#comment-17197609
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Stephan Ewen commented on FLINK-19016:
--------------------------------------
In my understanding, this is not possible.
As long as there is no crash, fsync or not does not make a difference. All
reads/writes are primarily through OS disk cache anyways. If there is a crash,
we do not complete the checkpoint. So it should make no difference to Flink.
I think there must be another explanation for this problem.
Do you have a way to reproduce this?
> Checksum mismatch when restore from RocksDB
> -------------------------------------------
>
> Key: FLINK-19016
> URL: https://issues.apache.org/jira/browse/FLINK-19016
> Project: Flink
> Issue Type: Bug
> Components: Runtime / Checkpointing
> Affects Versions: 1.11.1
> Reporter: Jiayi Liao
> Priority: Major
>
> The error stack is shown below:
> {code:java}
> Caused by: org.apache.flink.util.FlinkException: Could not restore keyed
> state backend for
> KeyedMapBundleOperator_44cfc1ca74b40bb44eed1f38f72b3ea9_(71/300) from any of
> the 1 provided restore options.
> at
> org.apache.flink.streaming.api.operators.BackendRestorerProcedure.createAndRestore(BackendRestorerProcedure.java:135)
> at
> org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.keyedStatedBackend(StreamTaskStateInitializerImpl.java:307)
> at
> org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.streamOperatorStateContext(StreamTaskStateInitializerImpl.java:135)
> ... 6 more
> Caused by: org.apache.flink.runtime.state.BackendBuildingException: Caught
> unexpected exception.
> at
> org.apache.flink.contrib.streaming.state.RocksDBKeyedStateBackendBuilder.build(RocksDBKeyedStateBackendBuilder.java:333)
> at
> org.apache.flink.contrib.streaming.state.RocksDBStateBackend.createKeyedStateBackend(RocksDBStateBackend.java:580)
> at
> org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.lambda$keyedStatedBackend$1(StreamTaskStateInitializerImpl.java:291)
> at
> org.apache.flink.streaming.api.operators.BackendRestorerProcedure.attemptCreateAndRestore(BackendRestorerProcedure.java:142)
> at
> org.apache.flink.streaming.api.operators.BackendRestorerProcedure.createAndRestore(BackendRestorerProcedure.java:121)
> ... 8 more
> Caused by: java.io.IOException: Error while opening RocksDB instance.
> at
> org.apache.flink.contrib.streaming.state.RocksDBOperationUtils.openDB(RocksDBOperationUtils.java:74)
> at
> org.apache.flink.contrib.streaming.state.restore.AbstractRocksDBRestoreOperation.openDB(AbstractRocksDBRestoreOperation.java:131)
> at
> org.apache.flink.contrib.streaming.state.restore.RocksDBIncrementalRestoreOperation.restoreFromLocalState(RocksDBIncrementalRestoreOperation.java:214)
> at
> org.apache.flink.contrib.streaming.state.restore.RocksDBIncrementalRestoreOperation.restoreFromRemoteState(RocksDBIncrementalRestoreOperation.java:188)
> at
> org.apache.flink.contrib.streaming.state.restore.RocksDBIncrementalRestoreOperation.restoreWithoutRescaling(RocksDBIncrementalRestoreOperation.java:162)
> at
> org.apache.flink.contrib.streaming.state.restore.RocksDBIncrementalRestoreOperation.restore(RocksDBIncrementalRestoreOperation.java:148)
> at
> org.apache.flink.contrib.streaming.state.RocksDBKeyedStateBackendBuilder.build(RocksDBKeyedStateBackendBuilder.java:277)
> ... 12 more
> Caused by: org.rocksdb.RocksDBException: checksum mismatch
> at org.rocksdb.RocksDB.open(Native Method)
> at org.rocksdb.RocksDB.open(RocksDB.java:286)
> at
> org.apache.flink.contrib.streaming.state.RocksDBOperationUtils.openDB(RocksDBOperationUtils.java:66)
> ... 18 more
> {code}
> The machine goes down because of hardware problem, then the job cannot
> restart successfully anymore. After digging a little bit, I found that
> RocksDB in Flink uses sync instead of fsync to synchronized the data with the
> disk. With sync operation, the RocksDB cannot guarantee that the current
> in-progress file can be persisted on disk in takeDBNativeCheckpoint.
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