Thomas Mueller created OAK-8991:
-----------------------------------
Summary: MarkSweepGarbageCollector: repeated warnings for files
that don't exist
Key: OAK-8991
URL: https://issues.apache.org/jira/browse/OAK-8991
Project: Jackrabbit Oak
Issue Type: Improvement
Components: blob
Reporter: Thomas Mueller
When using the MarkSweepGarbageCollector (using for example a file data store),
if the blob id file (from the BlobIdTracker) contains records that don't exist
in the datastore, then a warning is logged when trying to remove the
(unreferenced) file:
{noformat}
*WARN* org.apache.jackrabbit.oak.plugins.blob.MarkSweepGarbageCollector Error
occurred while deleting blob with id [...]
org.apache.jackrabbit.core.data.DataStoreException: Record ... does not exist
at
org.apache.jackrabbit.core.data.AbstractDataStore.getRecord(AbstractDataStore.java:59)
[org.apache.jackrabbit.jackrabbit-data:2.16.3]
at
org.apache.jackrabbit.oak.plugins.blob.datastore.OakFileDataStore.getRecordForId(OakFileDataStore.java:259)
[org.apache.jackrabbit.oak-blob-plugins:1.8.9]
at
org.apache.jackrabbit.oak.plugins.blob.datastore.DataStoreBlobStore.getRecordForId(DataStoreBlobStore.java:520)
[org.apache.jackrabbit.oak-blob-plugins:1.8.9]
at
org.apache.jackrabbit.oak.plugins.blob.datastore.DataStoreBlobStore.countDeleteChunks(DataStoreBlobStore.java:426)
[org.apache.jackrabbit.oak-blob-plugins:1.8.9]
at
org.apache.jackrabbit.oak.plugins.blob.MarkSweepGarbageCollector$BlobCollectionType.sweepInternal(MarkSweepGarbageCollector.java:859)
[org.apache.jackrabbit.oak-blob-plugins:1.8.9]
at
org.apache.jackrabbit.oak.plugins.blob.MarkSweepGarbageCollector.sweep(MarkSweepGarbageCollector.java:423)
[org.apache.jackrabbit.oak-blob-plugins:1.8.9]
at
org.apache.jackrabbit.oak.plugins.blob.MarkSweepGarbageCollector.markAndSweep(MarkSweepGarbageCollector.java:287)
[org.apache.jackrabbit.oak-blob-plugins:1.8.9]
at
org.apache.jackrabbit.oak.plugins.blob.MarkSweepGarbageCollector.collectGarbage(MarkSweepGarbageCollector.java:194)
[org.apache.jackrabbit.oak-blob-plugins:1.8.9]
{noformat}
That means it tried to remove a file that doesn't exist.
This indicates a problem in the process; for example, the blob id tracker
file(s) was/were restored from an older backup. (Possibly there are other cases
how this could occur).
Now, the next time the garbage collection is run, the same files will try to be
removed, and that again fails.
It would be better if the files that don't exist are removed from the blob id
tracker file, so that they are not tried to be removed later again and again.
If the blob id tracker file(s) are incorrect, I think it would be better to
delete and rebuild them, otherwise some of the unreferenced binaries will never
be removed. Possibly a warning should be logged, with instructions on how to
rebuild these files.
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