[jira] [Updated] (OAK-7339) Fix all sidegrades breaking with UnsupportedOperationException on MissingBlobStore by introducing LoopbackBlobStore

["Arek Kita (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/OAK-7339?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Arek Kita updated OAK-7339:
---------------------------
    Labels: intentToBackport  (was: )

> Fix all sidegrades breaking with UnsupportedOperationException on MissingBlobStore by introducing LoopbackBlobStore
> -------------------------------------------------------------------------------------------------------------------
>
>                 Key: OAK-7339
>                 URL: https://issues.apache.org/jira/browse/OAK-7339
>             Project: Jackrabbit Oak
>          Issue Type: Bug
>          Components: upgrade
>    Affects Versions: 1.6.0, 1.8.0
>            Reporter: Arek Kita
>            Assignee: Arek Kita
>            Priority: Major
>              Labels: intentToBackport
>             Fix For: 1.9.0
>
>
> h4. Problem
> In some edge cases when the binary under the same path (/content/asset1) is modified by 2 independent checkpoints: A & B the sidegrade without providing DataStore might fail with the following error:
> {noformat:title=An exception thrown by oak-upgrade tool}
> Caused by: java.lang.UnsupportedOperationException: null
>     at org.apache.jackrabbit.oak.upgrade.cli.blob.MissingBlobStore.getInputStream(MissingBlobStore.java:62)
>     at org.apache.jackrabbit.oak.plugins.blob.BlobStoreBlob.getNewStream(BlobStoreBlob.java:47)
>     at org.apache.jackrabbit.oak.plugins.segment.SegmentBlob.getNewStream(SegmentBlob.java:276)
>     at org.apache.jackrabbit.oak.plugins.segment.SegmentBlob.getNewStream(SegmentBlob.java:86)
>     at org.apache.jackrabbit.oak.plugins.memory.AbstractBlob$1.openStream(AbstractBlob.java:44)
>     at com.google.common.io.ByteSource.contentEquals(ByteSource.java:344)
>     at org.apache.jackrabbit.oak.plugins.memory.AbstractBlob.equal(AbstractBlob.java:67)
>     at org.apache.jackrabbit.oak.plugins.segment.SegmentBlob.equals(SegmentBlob.java:227)
>     at com.google.common.base.Objects.equal(Objects.java:60)
>     at org.apache.jackrabbit.oak.plugins.memory.AbstractPropertyState.equal(AbstractPropertyState.java:59)
>     at org.apache.jackrabbit.oak.plugins.segment.SegmentPropertyState.equals(SegmentPropertyState.java:242)
>     at org.apache.jackrabbit.oak.plugins.segment.SegmentNodeState.compareProperties(SegmentNodeState.java:617)
>     at org.apache.jackrabbit.oak.plugins.segment.SegmentNodeState.compareAgainstBaseState(SegmentNodeState.java:511)
> (the same nested methods)
>     at org.apache.jackrabbit.oak.plugins.segment.SegmentNodeState.compareAgainstBaseState(SegmentNodeState.java:604)
>     at org.apache.jackrabbit.oak.upgrade.PersistingDiff.diff(PersistingDiff.java:139)
>     at org.apache.jackrabbit.oak.upgrade.PersistingDiff.childNodeChanged(PersistingDiff.java:191)
>     at org.apache.jackrabbit.oak.plugins.segment.MapRecord$3.childNodeChanged(MapRecord.java:440)
>     at org.apache.jackrabbit.oak.plugins.segment.MapRecord.compare(MapRecord.java:483)
>     at org.apache.jackrabbit.oak.plugins.segment.MapRecord.compare(MapRecord.java:432)
>     at org.apache.jackrabbit.oak.plugins.segment.SegmentNodeState.compareAgainstBaseState(SegmentNodeState.java:604)
>     at org.apache.jackrabbit.oak.upgrade.PersistingDiff.diff(PersistingDiff.java:139)
>     at org.apache.jackrabbit.oak.upgrade.PersistingDiff.applyDiffOnNodeState(PersistingDiff.java:106)
>     at org.apache.jackrabbit.oak.upgrade.RepositorySidegrade.copyDiffToTarget(RepositorySidegrade.java:403)
>     at org.apache.jackrabbit.oak.upgrade.RepositorySidegrade.migrateWithCheckpoints(RepositorySidegrade.java:347)
> {noformat}
>  
> h4. Abstract of proposed solution
> The idea for migration is simple: instead of failing on:
> {code:java}public InputStream getInputStream(String blobId) throws IOException;
> {code}
> or
> {code:java}public int readBlob(String blobId, long pos, byte[] buff, int off, int length) throws IOException;
> {code}
> lets introduce a BlobStore implementation that acts similarly as a *localhost* interface that what you sent it will resend back to this interface.
> h4. How it works
> It works as a *localhost* interface, the same way: when *{{blobId}}* is requested... then *{{blobId}}* is served as a binary content instead *of throwing*: {{UnsupportedOperationException}}.
> This allows to act quickly on migrations that requires to compare binaries in order to satisfy requirements for checkpoints to be rewritten, copied from scratch.
> h4. Pros
>  * simplifies simple sidegrade migration use cases: you do not need anymore to include your DataStore (which slows that migration not necessary) on the command line when the migration is failing
>  * speeds up the migration as it doesn't require to reference BlobStore implementation in cases where binary references are only copied together with NodeStore inlined binaries
>  * you're always copying checkpoints which means (no need anymore for {{--skip-checkpoints}} option) that no full re-indexes are happening anymore after migration on migrated repository
> h4. Cons
>  * not visible effect to user that for a specific migration a DataStore is needed (whether you are running into this specific edge case)



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