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https://issues.apache.org/jira/browse/HDDS-16175?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Chi-Hsuan Huang updated HDDS-16175:
-----------------------------------
Affects Version/s: 2.1.0
2.1.1
2.2.0
> usedNamespace is charged on every hsync re-commit of the same key
> -----------------------------------------------------------------
>
> Key: HDDS-16175
> URL: https://issues.apache.org/jira/browse/HDDS-16175
> Project: Apache Ozone
> Issue Type: Bug
> Components: OM
> Affects Versions: 2.1.0, 2.2.0, 2.1.1
> Reporter: Chi-Hsuan Huang
> Priority: Major
>
> ### Problem
> A bucket's {{usedNamespace}} is charged once per key commit but refunded only
> once per key.
> Every hsync re-commit of the same key by the same client charges the counter
> again without
> ever adding a key, so a file that is hsync'd N times consumes N+1 namespace
> units while
> holding one name. Deleting the key refunds 1. The residue is permanent: after
> every key in
> the bucket has been deleted, {{usedNamespace}} stays at a non-zero value and
> never returns
> to 0. It permanently consumes the bucket's namespace quota, so
> {{OMKeyRequest.checkBucketQuotaInNamespace}} eventually rejects writes on a
> bucket that
> holds fewer keys than its quota allows. {{ozone sh bucket info}} and the
> Recon quota bar
> read the same persisted counter.
> This affects any hsync workload, HBase WALs in particular, on both OBS and
> FSO buckets.
> ### Root cause
> {{c351de9914}} (HDDS-13756, "Introduce Bucket Snapshot Used Bytes and
> SnapshotUsedNamespace
> in BucketInfo") hoisted {{incrUsedNamespace(1L)}} out of the {{else}} branch
> and placed it
> after the whole if/else chain:
> } else {
> checkBucketQuotaInNamespace(omBucketInfo, 1L);
> checkBucketQuotaInBytes(omMetadataManager, omBucketInfo,
> correctedSpace);
> - omBucketInfo.incrUsedNamespace(1L);
> }
> -
> + omBucketInfo.incrUsedNamespace(1L);
> Every commit now increments the counter, including the {{isSameHsyncKey}}
> branch at
> {{OMKeyCommitRequest.java:324}}, which handles a re-commit of a key the same
> client already
> hsync'd. That branch previously did not touch namespace, and that was
> deliberate:
> {{df4df20371}} (HDDS-7965, "Quota needs to be updated correctly for Hsync")
> introduced it
> precisely to settle only the byte delta for an hsync re-commit:
> - if (keyToDelete != null && !omBucketInfo.getIsVersionEnabled()) {
> + if (keyToDelete != null && isHSync) {
> + correctedSpace -= keyToDelete.getReplicatedSize();
> + checkBucketQuotaInBytes(omMetadataManager, omBucketInfo,
> correctedSpace);
> + } else if (keyToDelete != null &&
> !omBucketInfo.getIsVersionEnabled()) {
> ({{d7e5b3a3fd}}, HDDS-10770, later narrowed the condition from {{isHSync}} to
> {{isSameHsyncKey}}; the intent was unchanged.) HDDS-13756 therefore reverts
> HDDS-7965 for
> the namespace counter while leaving its byte handling in place.
> The refund side is unchanged: {{OMKeyDeleteRequest.java:169}} refunds a flat
> {{decrUsedNamespace(1L, ...)}} per key, and the neighbouring line 168
> releases bytes via
> {{sumBlockLengths}}. Bytes are therefore symmetric while namespace is not.
> Both commit paths carry the hoisted increment:
> * {{OMKeyCommitRequest.java:375}}
> * {{OMKeyCommitRequestWithFSO.java:307}}
> ### Expected semantics
> Every other surface treats {{usedNamespace}} as a count of keys:
> * {{a58d3f5a00}} (HDDS-4277) introduced the counter with the commit body "add
> namespaceQuotaUsage and update it when create and delete key in a bucket".
> * {{hadoop-hdds/docs/content/feature/Quota.md:57}}: "When bucket namespace
> quota is enabled,
> the total number of keys under the bucket, cannot exceed the bucket
> namespace quota", and
> "Namespace quota is a number that represents how many unique names can be
> used".
> * All six refund sites ({{OMKeyDeleteRequest}}, {{OMKeyDeleteRequestWithFSO}},
> {{OMKeysDeleteRequest}}, {{OMDirectoriesPurgeRequestWithFSO}},
> {{OMKeyPurgeRequest}}, and
> the overwrite branch of {{OMKeyCommitRequest}}) refund one unit per key.
> * {{OzoneRpcClientTests.java:1921}}: "Test create a file twice will not
> increase
> usedNamespace twice".
> No commit message, javadoc, document or test in the repository states that
> re-committing a
> key should consume an additional namespace unit.
> ### Fix
> Charge {{incrUsedNamespace(1L)}} only on the paths that actually add a key,
> i.e. move it
> back inside the branches rather than after the chain, in both
> {{OMKeyCommitRequest}} and
> {{OMKeyCommitRequestWithFSO}}.
> The regression shipped unnoticed because no test asserts {{usedNamespace}}
> across repeated
> hsync commits; the quota tests around this code assert {{getUsedBytes()}}
> only. A fix should
> add an assertion that hsync'ing a key N times leaves {{usedNamespace}} at 1,
> and that the
> counter returns to 0 after the key is deleted.
> ### Note on bucket versioning
> The same hoisted increment also charges once per version on a
> versioning-enabled bucket,
> because {{ff351025bc}} (HDDS-6709) routed versioned overwrites into the
> {{else}} branch that
> carries the increment. That half is out of scope here: per the discussion on
> HDDS-16127,
> there is no code path that exercises bucket versioning today, and HDDS-15728
> object
> versioning stores each version as a separate {{OmKeyInfo}}. This issue is
> limited to the
> hsync path, which is exercised by ordinary non-versioned buckets.
> The stale comment at {{OMKeyCommitRequest.java:322-323}}, "if keyToDelete
> isn't null,
> usedNamespace needn't check and increase" (introduced by {{9055a11216}},
> HDDS-6556), still
> contradicts the code and can be corrected alongside the fix.
> ### Notes
> Found while scoping HDDS-16127. Pinned source commit 4766aa8609. Analysis
> assisted by AI
> tooling (Claude Code, Opus 5).
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