Denser in-memory representation of ShardBlobsToDelete
#109848
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Today each blob to be deleted at the end of a snapshot delete costs us ~80B of heap, and sometimes that can add up to GiBs of temporary heap usage in total. This commit changes the in-memory representation to use a compressed stream of pure bytes, which should be more than 4x denser. Partially mitigates elastic#108278
DaveCTurner
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:Distributed Coordination/Snapshot/Restore
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Hi @DaveCTurner, I've created a changelog YAML for you. |
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…ed-ShardBlobsToDelete
mhl-b
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Jun 19, 2024
| shardDeleteResults.add(new ShardSnapshotMetaDeleteResult(indexId, shardId, newGeneration, blobsToDelete)); | ||
| try { | ||
| shardGenerationsBuilder.put(indexId, shardId, newGeneration); | ||
| new ShardSnapshotMetaDeleteResult(Objects.requireNonNull(indexId.getId()), shardId, blobsToDelete).writeTo(compressed); |
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As far as I understand blobsToDelete is already occupy memory we want to optimize. Adding in-memory compression will temporary increase heap usage by 20%? How do you know that blobsToDelete will be GC-ed after compression?
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There's nothing else retaining it apart from the reference in ShardBlobsToDelete#shardDeleteResults.
mhl-b
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Jun 20, 2024
pxsalehi
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Jun 20, 2024
server/src/main/java/org/elasticsearch/repositories/blobstore/BlobStoreRepository.java
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Today each blob to be deleted at the end of a snapshot delete costs us
~80B of heap, and sometimes that can add up to GiBs of temporary heap
usage in total. This commit changes the in-memory representation to use
a compressed stream of pure bytes, which should be more than 4x denser.
Partially mitigates #108278